RE: [PATCH v10 1/8] spi: Add multi-cs memories support in SPI core

["Mahapatra, Amit Kumar" <amit.kumar-mahapatra@xxxxxxx>]

Hello Stefan,

> -----Original Message-----
> From: Stefan Binding <sbinding@xxxxxxxxxxxxxxxxxxxxx>
> Sent: Tuesday, November 21, 2023 7:28 PM
> To: Mahapatra, Amit Kumar <amit.kumar-mahapatra@xxxxxxx>;
> broonie@xxxxxxxxxx; tudor.ambarus@xxxxxxxxxx; pratyush@xxxxxxxxxx;
> miquel.raynal@xxxxxxxxxxx; richard@xxxxxx; vigneshr@xxxxxx
> Cc: linux-spi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> michael@xxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx;
> nicolas.ferre@xxxxxxxxxxxxx; alexandre.belloni@xxxxxxxxxxx;
> claudiu.beznea@xxxxxxxxx; Simek, Michal <michal.simek@xxxxxxx>; linux-
> arm-kernel@xxxxxxxxxxxxxxxxxxx; git (AMD-Xilinx) <git@xxxxxxx>;
> amitrkcian2002@xxxxxxxxx; patches@xxxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v10 1/8] spi: Add multi-cs memories support in SPI core
> 
> 
> On 21/11/2023 07:39, Mahapatra, Amit Kumar wrote:
> > Hello Stefan,
> >
> >> -----Original Message-----
> >> From: Stefan Binding <sbinding@xxxxxxxxxxxxxxxxxxxxx>
> >> Sent: Monday, November 20, 2023 8:00 PM
> >> To: Mahapatra, Amit Kumar <amit.kumar-mahapatra@xxxxxxx>;
> >> broonie@xxxxxxxxxx; tudor.ambarus@xxxxxxxxxx; pratyush@xxxxxxxxxx;
> >> miquel.raynal@xxxxxxxxxxx; richard@xxxxxx; vigneshr@xxxxxx
> >> Cc: linux-spi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> >> michael@xxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx;
> >> nicolas.ferre@xxxxxxxxxxxxx; alexandre.belloni@xxxxxxxxxxx;
> >> claudiu.beznea@xxxxxxxxx; Simek, Michal <michal.simek@xxxxxxx>;
> >> linux- arm-kernel@xxxxxxxxxxxxxxxxxxx; git (AMD-Xilinx)
> >> <git@xxxxxxx>; amitrkcian2002@xxxxxxxxx;
> >> patches@xxxxxxxxxxxxxxxxxxxxx
> >> Subject: Re: [PATCH v10 1/8] spi: Add multi-cs memories support in
> >> SPI core
> >>
> >>
> >> On 18/11/2023 13:54, Amit Kumar Mahapatra wrote:
> >>> AMD-Xilinx GQSPI controller has two advanced mode that allows the
> >>> controller to consider two flashes as one single device.
> >>>
> >>> One of these two mode is the parallel mode in which each byte of
> >>> data is stored in both devices, the even bits in the lower flash &
> >>> the odd bits in the upper flash. The byte split is automatically
> >>> handled by the QSPI controller.
> >>>
> >>> The other mode is the stacked mode in which both the flashes share
> >>> the same SPI bus but each of the device contain half of the data. In
> >>> this mode, the controller does not follow CS requests but instead
> >>> internally wires the two CS levels with the value of the most
> >>> significant
> >> address bit.
> >>> For supporting both these modes SPI core need to be updated for
> >>> providing multiple CS for a single SPI device.
> >>>
> >>> For adding multi CS support the SPI device need to be aware of all
> >>> the CS values. So, the "chip_select" member in the spi_device
> >>> structure is now an array that holds all the CS values.
> >>>
> >>> spi_device structure now has a "cs_index_mask" member. This acts as
> >>> an index to the chip_select array. If nth bit of spi->cs_index_mask
> >>> is set then the driver would assert spi->chip_select[n].
> >>>
> >>> In parallel mode all the chip selects are asserted/de-asserted
> >>> simultaneously and each byte of data is stored in both devices, the
> >>> even bits in one, the odd bits in the other. The split is
> >>> automatically handled by the GQSPI controller. The GQSPI controller
> >>> supports a maximum of two flashes connected in parallel mode. A
> >>> SPI_CONTROLLER_MULTI_CS flag bit is added in the spi controller
> >>> flags, through ctlr->flags the spi core will make sure that the
> >>> controller is capable of handling multiple chip selects at once.
> >>>
> >>> For supporting multiple CS via GPIO the cs_gpiod member of the
> >>> spi_device structure is now an array that holds the gpio descriptor
> >>> for each chipselect.
> >>>
> >>> CS GPIO is not tested due to unavailability of necessary hardware setup.
> >>>
> >>> Signed-off-by: Amit Kumar Mahapatra <amit.kumar-
> mahapatra@xxxxxxx>
> >>> ---
> >>> Hello @Stefen,
> >>> We restructured the SPI core implementation, for handling arbitrary
> >>> number of devices connected in parallel(multi-cs) or stacked mode.
> >>> We have tested this updated patch on native-cs setup but couldn't
> >>> test cs-gpio due to unavailability of a proper setup. If possible,
> >>> could you please retest the cs-gpio use case with this updated patch
> >>> and provide
> >> your feedback.
> >>
> >> Hi,
> >>
> >> I tested this chain on 2 different systems using GPIOs as chip
> >> selects, and see the same error on both:
> >> [    2.842045] pxa2xx-spi pxa2xx-spi.6: chipselect 0 already in use
> >>
> >> Let me know if you need any further testing.
> >>
> >> Thanks,
> >>
> >> Stefan Binding
> >>
> >>> ---
> >>>    drivers/spi/spi.c       | 192 +++++++++++++++++++++++++++++++---------
> >>>    include/linux/spi/spi.h |  51 ++++++++---
> >>>    2 files changed, 191 insertions(+), 52 deletions(-)
> >>>
> >>> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index
> >>> 8ead7acb99f3..ff66147ba95f 100644
> >>> --- a/drivers/spi/spi.c
> >>> +++ b/drivers/spi/spi.c
> >>> @@ -612,10 +612,21 @@ static int spi_dev_check(struct device *dev,
> >>> void
> >> *data)
> >>>    {
> >>>    	struct spi_device *spi = to_spi_device(dev);
> >>>    	struct spi_device *new_spi = data;
> >>> -
> >>> -	if (spi->controller == new_spi->controller &&
> >>> -	    spi_get_chipselect(spi, 0) == spi_get_chipselect(new_spi, 0))
> >>> -		return -EBUSY;
> >>> +	int idx, nw_idx;
> >>> +	u8 cs, cs_nw;
> >>> +
> >>> +	if (spi->controller == new_spi->controller) {
> >>> +		for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> >>> +			cs = spi_get_chipselect(spi, idx);
> >>> +			for (nw_idx = 0; nw_idx < SPI_CS_CNT_MAX;
> >> nw_idx++) {
> >>> +				cs_nw = spi_get_chipselect(spi, nw_idx);
> > Thank you for dedicating your time to test my patch.
> > As per my analysis the error is reported from here as we are supplying
> > the former SPI device structure to retrieve the CS value for the new
> > SPI devices.
> > To fix this, could you kindly substitute the above line with
> >
> > cs_nw = spi_get_chipselect(new_spi, nw_idx);
> >
> > and rerun your tests?
> > If it works correctly, I will incorporate this fix into my upcoming
> > series.
> >
> > Regards,
> > Amit
> 
> Hi,
> 
> I still see the same error:
> 
> [    2.748546] pxa2xx-spi pxa2xx-spi.6: chipselect 0 already in use

Thank you for the quick testing. For further analysis I have incorporated 
additional debug prints on top of 1/8 patch. The corresponding diff is 
shared below. Kindly implement the specified changes, rerun your test and 
share the kernel logs.

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index ff66147ba95f..7f59ea81593d 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -618,8 +618,10 @@ static int spi_dev_check(struct device *dev, void *data)
        if (spi->controller == new_spi->controller) {
                for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
                        cs = spi_get_chipselect(spi, idx);
+                       printk("%s() [%d] CS[%d] = [%d]\n", __func__, __LINE__, idx, cs);
                        for (nw_idx = 0; nw_idx < SPI_CS_CNT_MAX; nw_idx++) {
-                               cs_nw = spi_get_chipselect(spi, nw_idx);
+                               cs_nw = spi_get_chipselect(new_spi, nw_idx);
+                               printk("%s() [%d] CS_NEW[%d] = [%d]\n", __func__, __LINE__, nw_idx, cs_nw);
                                if (cs != 0xFF && cs_nw != 0xFF && cs == cs_nw) {
                                        dev_err(dev, "chipselect %d already in use\n", cs_nw);
                                        return -EBUSY;
@@ -659,8 +661,10 @@ static int __spi_add_device(struct spi_device *spi)
         */
        for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
                cs = spi_get_chipselect(spi, idx);
+               printk("%s() [%d] CS[%d] = [%d]\n", __func__, __LINE__, idx, cs);
                for (nw_idx = idx + 1; nw_idx < SPI_CS_CNT_MAX; nw_idx++) {
                        nw_cs = spi_get_chipselect(spi, nw_idx);
+                       printk("%s() [%d] CS_NEW[%d] = [%d]\n", __func__, __LINE__, nw_idx, nw_cs);
                        if (cs != 0xFF && nw_cs != 0xFF && cs == nw_cs) {
                                dev_err(dev, "chipselect %d already in use\n", nw_cs);
                                return -EBUSY;
@@ -2401,6 +2405,9 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
        for (idx = 0; idx < rc; idx++)
                spi_set_chipselect(spi, idx, cs[idx]);
 
+       for (idx = 0; idx < SPI_CS_CNT_MAX; idx++)
+               printk("%s() [%d] CS[%d] = [%d]\n", __func__, __LINE__, idx, spi_get_chipselect(spi, idx));
+
        /* spi->chip_select[i] gives the corresponding physical CS for logical CS i
         * logical CS number is represented by setting the ith bit in spi->cs_index_mask
         * So, for example, if spi->cs_index_mask = 0x01 then logical CS number is 0 and

Regards,
Amit
 
> 
> Thanks,
> 
> Stefan
> 
> >
> >>> +				if (cs != 0xFF && cs_nw != 0xFF && cs ==
> >> cs_nw) {
> >>> +					dev_err(dev, "chipselect %d already in
> >> use\n", cs_nw);
> >>> +					return -EBUSY;
> >>> +				}
> >>> +			}
> >>> +		}
> >>> +	}
> >>>    	return 0;
> >>>    }
> >>>
> >>> @@ -629,13 +640,32 @@ static int __spi_add_device(struct spi_device
> *spi)
> >>>    {
> >>>    	struct spi_controller *ctlr = spi->controller;
> >>>    	struct device *dev = ctlr->dev.parent;
> >>> -	int status;
> >>> +	int status, idx, nw_idx;
> >>> +	u8 cs, nw_cs;
> >>> +
> >>> +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> >>> +		/* Chipselects are numbered 0..max; validate. */
> >>> +		cs = spi_get_chipselect(spi, idx);
> >>> +		if (cs != 0xFF && cs >= ctlr->num_chipselect) {
> >>> +			dev_err(dev, "cs%d >= max %d\n",
> >> spi_get_chipselect(spi, idx),
> >>> +				ctlr->num_chipselect);
> >>> +			return -EINVAL;
> >>> +		}
> >>> +	}
> >>>
> >>> -	/* Chipselects are numbered 0..max; validate. */
> >>> -	if (spi_get_chipselect(spi, 0) >= ctlr->num_chipselect) {
> >>> -		dev_err(dev, "cs%d >= max %d\n", spi_get_chipselect(spi, 0),
> >>> -			ctlr->num_chipselect);
> >>> -		return -EINVAL;
> >>> +	/*
> >>> +	 * Make sure that multiple logical CS doesn't map to the same
> >> physical CS.
> >>> +	 * For example, spi->chip_select[0] != spi->chip_select[1] and so on.
> >>> +	 */
> >>> +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> >>> +		cs = spi_get_chipselect(spi, idx);
> >>> +		for (nw_idx = idx + 1; nw_idx < SPI_CS_CNT_MAX; nw_idx++) {
> >>> +			nw_cs = spi_get_chipselect(spi, nw_idx);
> >>> +			if (cs != 0xFF && nw_cs != 0xFF && cs == nw_cs) {
> >>> +				dev_err(dev, "chipselect %d already in use\n",
> >> nw_cs);
> >>> +				return -EBUSY;
> >>> +			}
> >>> +		}
> >>>    	}
> >>>
> >>>    	/* Set the bus ID string */
> >>> @@ -647,11 +677,8 @@ static int __spi_add_device(struct spi_device
> *spi)
> >>>    	 * its configuration.
> >>>    	 */
> >>>    	status = bus_for_each_dev(&spi_bus_type, NULL, spi, spi_dev_check);
> >>> -	if (status) {
> >>> -		dev_err(dev, "chipselect %d already in use\n",
> >>> -				spi_get_chipselect(spi, 0));
> >>> +	if (status)
> >>>    		return status;
> >>> -	}
> >>>
> >>>    	/* Controller may unregister concurrently */
> >>>    	if (IS_ENABLED(CONFIG_SPI_DYNAMIC) && @@ -659,8 +686,15 @@
> >> static
> >>> int __spi_add_device(struct spi_device *spi)
> >>>    		return -ENODEV;
> >>>    	}
> >>>
> >>> -	if (ctlr->cs_gpiods)
> >>> -		spi_set_csgpiod(spi, 0, ctlr->cs_gpiods[spi_get_chipselect(spi,
> >> 0)]);
> >>> +	if (ctlr->cs_gpiods) {
> >>> +		u8 cs;
> >>> +
> >>> +		for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> >>> +			cs = spi_get_chipselect(spi, idx);
> >>> +			if (cs != 0xFF)
> >>> +				spi_set_csgpiod(spi, idx, ctlr->cs_gpiods[cs]);
> >>> +		}
> >>> +	}
> >>>
> >>>    	/*
> >>>    	 * Drivers may modify this initial i/o setup, but will @@ -701,6
> >>> +735,9 @@ int spi_add_device(struct spi_device *spi)
> >>>    	struct spi_controller *ctlr = spi->controller;
> >>>    	int status;
> >>>
> >>> +	/* Set the bus ID string */
> >>> +	spi_dev_set_name(spi);
> >>> +
> >>>    	mutex_lock(&ctlr->add_lock);
> >>>    	status = __spi_add_device(spi);
> >>>    	mutex_unlock(&ctlr->add_lock);
> >>> @@ -942,32 +979,51 @@ static void spi_res_release(struct
> >>> spi_controller
> >> *ctlr, struct spi_message *mes
> >>>    }
> >>>
> >>>
> >>> /*------------------------------------------------------------------
> >>> --
> >>> -----*/
> >>> +static inline bool spi_is_last_cs(struct spi_device *spi) {
> >>> +	u8 idx;
> >>> +	bool last = false;
> >>> +
> >>> +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> >>> +		if ((spi->cs_index_mask >> idx) & 0x01) {
> >>> +			if (spi->controller->last_cs[idx] ==
> >> spi_get_chipselect(spi, idx))
> >>> +				last = true;
> >>> +		}
> >>> +	}
> >>> +	return last;
> >>> +}
> >>> +
> >>>
> >>>    static void spi_set_cs(struct spi_device *spi, bool enable, bool force)
> >>>    {
> >>>    	bool activate = enable;
> >>> +	u8 idx;
> >>>
> >>>    	/*
> >>>    	 * Avoid calling into the driver (or doing delays) if the chip select
> >>>    	 * isn't actually changing from the last time this was called.
> >>>    	 */
> >>> -	if (!force && ((enable && spi->controller->last_cs ==
> >> spi_get_chipselect(spi, 0)) ||
> >>> -		       (!enable && spi->controller->last_cs !=
> >> spi_get_chipselect(spi, 0))) &&
> >>> +	if (!force && ((enable && spi->controller->last_cs_index_mask ==
> >>> +spi-
> >>> cs_index_mask &&
> >>> +			spi_is_last_cs(spi)) ||
> >>> +		       (!enable && spi->controller->last_cs_index_mask == spi-
> >>> cs_index_mask &&
> >>> +			!spi_is_last_cs(spi))) &&
> >>>    	    (spi->controller->last_cs_mode_high == (spi->mode &
> >> SPI_CS_HIGH)))
> >>>    		return;
> >>>
> >>>    	trace_spi_set_cs(spi, activate);
> >>>
> >>> -	spi->controller->last_cs = enable ? spi_get_chipselect(spi, 0) : -1;
> >>> +	spi->controller->last_cs_index_mask = spi->cs_index_mask;
> >>> +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++)
> >>> +		spi->controller->last_cs[idx] = enable ? spi_get_chipselect(spi,
> >> 0)
> >>> +: -1;
> >>>    	spi->controller->last_cs_mode_high = spi->mode & SPI_CS_HIGH;
> >>>
> >>> -	if ((spi_get_csgpiod(spi, 0) || !spi->controller->set_cs_timing) &&
> >> !activate)
> >>> -		spi_delay_exec(&spi->cs_hold, NULL);
> >>> -
> >>>    	if (spi->mode & SPI_CS_HIGH)
> >>>    		enable = !enable;
> >>>
> >>> -	if (spi_get_csgpiod(spi, 0)) {
> >>> +	if (spi_is_csgpiod(spi)) {
> >>> +		if (!spi->controller->set_cs_timing && !activate)
> >>> +			spi_delay_exec(&spi->cs_hold, NULL);
> >>> +
> >>>    		if (!(spi->mode & SPI_NO_CS)) {
> >>>    			/*
> >>>    			 * Historically ACPI has no means of the GPIO polarity
> >> and @@
> >>> -979,26 +1035,38 @@ static void spi_set_cs(struct spi_device *spi,
> >>> bool
> >> enable, bool force)
> >>>    			 * ambiguity. That's why we use enable, that takes
> >> SPI_CS_HIGH
> >>>    			 * into account.
> >>>    			 */
> >>> -			if (has_acpi_companion(&spi->dev))
> >>> -
> >> 	gpiod_set_value_cansleep(spi_get_csgpiod(spi, 0), !enable);
> >>> -			else
> >>> -				/* Polarity handled by GPIO library */
> >>> -
> >> 	gpiod_set_value_cansleep(spi_get_csgpiod(spi, 0), activate);
> >>> +			for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> >>> +				if (((spi->cs_index_mask >> idx) & 0x01) &&
> >>> +				    spi_get_csgpiod(spi, idx)) {
> >>> +					if (has_acpi_companion(&spi->dev))
> >>> +
> >> 	gpiod_set_value_cansleep(spi_get_csgpiod(spi, idx),
> >>> +
> >> !enable);
> >>> +					else
> >>> +						/* Polarity handled by GPIO
> >> library */
> >>> +
> >> 	gpiod_set_value_cansleep(spi_get_csgpiod(spi, idx),
> >>> +
> >> activate);
> >>> +
> >>> +					if (activate)
> >>> +						spi_delay_exec(&spi-
> >>> cs_setup, NULL);
> >>> +					else
> >>> +						spi_delay_exec(&spi-
> >>> cs_inactive, NULL);
> >>> +				}
> >>> +			}
> >>>    		}
> >>>    		/* Some SPI masters need both GPIO CS & slave_select */
> >>>    		if ((spi->controller->flags & SPI_CONTROLLER_GPIO_SS) &&
> >>>    		    spi->controller->set_cs)
> >>>    			spi->controller->set_cs(spi, !enable);
> >>> +
> >>> +		if (!spi->controller->set_cs_timing) {
> >>> +			if (activate)
> >>> +				spi_delay_exec(&spi->cs_setup, NULL);
> >>> +			else
> >>> +				spi_delay_exec(&spi->cs_inactive, NULL);
> >>> +		}
> >>>    	} else if (spi->controller->set_cs) {
> >>>    		spi->controller->set_cs(spi, !enable);
> >>>    	}
> >>> -
> >>> -	if (spi_get_csgpiod(spi, 0) || !spi->controller->set_cs_timing) {
> >>> -		if (activate)
> >>> -			spi_delay_exec(&spi->cs_setup, NULL);
> >>> -		else
> >>> -			spi_delay_exec(&spi->cs_inactive, NULL);
> >>> -	}
> >>>    }
> >>>
> >>>    #ifdef CONFIG_HAS_DMA
> >>> @@ -2222,8 +2290,8 @@ static void of_spi_parse_dt_cs_delay(struct
> >> device_node *nc,
> >>>    static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device
> *spi,
> >>>    			   struct device_node *nc)
> >>>    {
> >>> -	u32 value;
> >>> -	int rc;
> >>> +	u32 value, cs[SPI_CS_CNT_MAX];
> >>> +	int rc, idx;
> >>>
> >>>    	/* Mode (clock phase/polarity/etc.) */
> >>>    	if (of_property_read_bool(nc, "spi-cpha")) @@ -2295,14 +2363,52
> >> @@
> >>> static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
> >>>    		return 0;
> >>>    	}
> >>>
> >>> +	if (ctlr->num_chipselect > SPI_CS_CNT_MAX) {
> >>> +		dev_err(&ctlr->dev, "No. of CS is more than max. no. of
> >> supported CS\n");
> >>> +		return -EINVAL;
> >>> +	}
> >>> +
> >>> +	/*
> >>> +	 * Zero(0) is a valid physical CS value and can be located at any
> >>> +	 * logical CS in the spi->chip_select[]. If all the physical CS
> >>> +	 * are initialized to 0 then It would be difficult to differentiate
> >>> +	 * between a valid physical CS 0 & an unused logical CS whose
> >> physical
> >>> +	 * CS can be 0. As a solution to this issue initialize all the CS to 0xFF.
> >>> +	 * Now all the unused logical CS will have 0xFF physical CS value
> >>> +& can
> >> be
> >>> +	 * ignore while performing physical CS validity checks.
> >>> +	 */
> >>> +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++)
> >>> +		spi_set_chipselect(spi, idx, 0xFF);
> >>> +
> >>>    	/* Device address */
> >>> -	rc = of_property_read_u32(nc, "reg", &value);
> >>> -	if (rc) {
> >>> +	rc = of_property_read_variable_u32_array(nc, "reg", &cs[0], 1,
> >>> +						 SPI_CS_CNT_MAX);
> >>> +	if (rc < 0) {
> >>>    		dev_err(&ctlr->dev, "%pOF has no valid 'reg' property
> >> (%d)\n",
> >>>    			nc, rc);
> >>>    		return rc;
> >>>    	}
> >>> -	spi_set_chipselect(spi, 0, value);
> >>> +	if (rc > ctlr->num_chipselect) {
> >>> +		dev_err(&ctlr->dev, "%pOF has number of CS > ctlr-
> >>> num_chipselect (%d)\n",
> >>> +			nc, rc);
> >>> +		return rc;
> >>> +	}
> >>> +	if ((of_property_read_bool(nc, "parallel-memories")) &&
> >>> +	    (!(ctlr->flags & SPI_CONTROLLER_MULTI_CS))) {
> >>> +		dev_err(&ctlr->dev, "SPI controller doesn't support multi
> >> CS\n");
> >>> +		return -EINVAL;
> >>> +	}
> >>> +	for (idx = 0; idx < rc; idx++)
> >>> +		spi_set_chipselect(spi, idx, cs[idx]);
> >>> +
> >>> +	/* spi->chip_select[i] gives the corresponding physical CS for
> >>> +logical CS
> >> i
> >>> +	 * logical CS number is represented by setting the ith bit in spi-
> >>> cs_index_mask
> >>> +	 * So, for example, if spi->cs_index_mask = 0x01 then logical CS
> >> number is 0 and
> >>> +	 * spi->chip_select[0] will give the physical CS.
> >>> +	 * By default spi->chip_select[0] will hold the physical CS number
> >>> +so,
> >> set
> >>> +	 * spi->cs_index_mask as 0x01.
> >>> +	 */
> >>> +	spi->cs_index_mask = 0x01;
> >>>
> >>>    	/* Device speed */
> >>>    	if (!of_property_read_u32(nc, "spi-max-frequency", &value)) @@
> >>> -3100,6 +3206,7 @@ int spi_register_controller(struct spi_controller *ctlr)
> >>>    	struct boardinfo	*bi;
> >>>    	int			first_dynamic;
> >>>    	int			status;
> >>> +	int			idx;
> >>>
> >>>    	if (!dev)
> >>>    		return -ENODEV;
> >>> @@ -3164,7 +3271,8 @@ int spi_register_controller(struct
> >>> spi_controller
> >> *ctlr)
> >>>    	}
> >>>
> >>>    	/* Setting last_cs to -1 means no chip selected */
> >>> -	ctlr->last_cs = -1;
> >>> +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++)
> >>> +		ctlr->last_cs[idx] = -1;
> >>>
> >>>    	status = device_add(&ctlr->dev);
> >>>    	if (status < 0)
> >>> @@ -3889,7 +3997,7 @@ static int __spi_validate(struct spi_device
> >>> *spi,
> >> struct spi_message *message)
> >>>    	 * cs_change is set for each transfer.
> >>>    	 */
> >>>    	if ((spi->mode & SPI_CS_WORD) && (!(ctlr->mode_bits &
> >> SPI_CS_WORD) ||
> >>> -					  spi_get_csgpiod(spi, 0))) {
> >>> +					  spi_is_csgpiod(spi))) {
> >>>    		size_t maxsize = BITS_TO_BYTES(spi->bits_per_word);
> >>>    		int ret;
> >>>
> >>> diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index
> >>> 7b4baff63c5c..871d3a6d879b 100644
> >>> --- a/include/linux/spi/spi.h
> >>> +++ b/include/linux/spi/spi.h
> >>> @@ -20,6 +20,9 @@
> >>>
> >>>    #include <uapi/linux/spi/spi.h>
> >>>
> >>> +/* Max no. of CS supported per spi device */ #define SPI_CS_CNT_MAX
> >>> +4
> >>> +
> >>>    struct dma_chan;
> >>>    struct software_node;
> >>>    struct ptp_system_timestamp;
> >>> @@ -132,7 +135,8 @@ extern void
> >> spi_transfer_cs_change_delay_exec(struct spi_message *msg,
> >>>     * @max_speed_hz: Maximum clock rate to be used with this chip
> >>>     *	(on this board); may be changed by the device's driver.
> >>>     *	The spi_transfer.speed_hz can override this for each transfer.
> >>> - * @chip_select: Chipselect, distinguishing chips handled by @controller.
> >>> + * @chip_select: Array of physical chipselect, spi->chipselect[i] gives
> >>> + *	the corresponding physical CS for logical CS i.
> >>>     * @mode: The spi mode defines how data is clocked out and in.
> >>>     *	This may be changed by the device's driver.
> >>>     *	The "active low" default for chipselect mode can be overridden
> >>> @@ -157,8 +161,8 @@ extern void
> >> spi_transfer_cs_change_delay_exec(struct spi_message *msg,
> >>>     *	the device will bind to the named driver and only the named driver.
> >>>     *	Do not set directly, because core frees it; use driver_set_override() to
> >>>     *	set or clear it.
> >>> - * @cs_gpiod: GPIO descriptor of the chipselect line (optional, NULL
> when
> >>> - *	not using a GPIO line)
> >>> + * @cs_gpiod: Array of GPIO descriptors of the corresponding
> >>> + chipselect
> >> lines
> >>> + *	(optional, NULL when not using a GPIO line)
> >>>     * @word_delay: delay to be inserted between consecutive
> >>>     *	words of a transfer
> >>>     * @cs_setup: delay to be introduced by the controller after CS
> >>> is asserted @@ -167,6 +171,7 @@ extern void
> >> spi_transfer_cs_change_delay_exec(struct spi_message *msg,
> >>>     *	deasserted. If @cs_change_delay is used from @spi_transfer, then
> >> the
> >>>     *	two delays will be added up.
> >>>     * @pcpu_statistics: statistics for the spi_device
> >>> + * @cs_index_mask: Bit mask of the active chipselect(s) in the
> >>> + chipselect array
> >>>     *
> >>>     * A @spi_device is used to interchange data between an SPI slave
> >>>     * (usually a discrete chip) and CPU memory.
> >>> @@ -182,7 +187,7 @@ struct spi_device {
> >>>    	struct spi_controller	*controller;
> >>>    	struct spi_controller	*master;	/* Compatibility layer */
> >>>    	u32			max_speed_hz;
> >>> -	u8			chip_select;
> >>> +	u8			chip_select[SPI_CS_CNT_MAX];
> >>>    	u8			bits_per_word;
> >>>    	bool			rt;
> >>>    #define SPI_NO_TX		BIT(31)		/* No transmit wire */
> >>> @@ -213,7 +218,7 @@ struct spi_device {
> >>>    	void			*controller_data;
> >>>    	char			modalias[SPI_NAME_SIZE];
> >>>    	const char		*driver_override;
> >>> -	struct gpio_desc	*cs_gpiod;	/* Chip select GPIO descriptor
> >> */
> >>> +	struct gpio_desc	*cs_gpiod[SPI_CS_CNT_MAX];	/* Chip select
> >> gpio desc */
> >>>    	struct spi_delay	word_delay; /* Inter-word delay */
> >>>    	/* CS delays */
> >>>    	struct spi_delay	cs_setup;
> >>> @@ -223,6 +228,13 @@ struct spi_device {
> >>>    	/* The statistics */
> >>>    	struct spi_statistics __percpu	*pcpu_statistics;
> >>>
> >>> +	/* Bit mask of the chipselect(s) that the driver need to use from
> >>> +	 * the chipselect array.When the controller is capable to handle
> >>> +	 * multiple chip selects & memories are connected in parallel
> >>> +	 * then more than one bit need to be set in cs_index_mask.
> >>> +	 */
> >>> +	u32			cs_index_mask : SPI_CS_CNT_MAX;
> >>> +
> >>>    	/*
> >>>    	 * Likely need more hooks for more protocol options affecting how
> >>>    	 * the controller talks to each chip, like:
> >>> @@ -279,22 +291,33 @@ static inline void *spi_get_drvdata(const
> >>> struct spi_device *spi)
> >>>
> >>>    static inline u8 spi_get_chipselect(const struct spi_device *spi, u8 idx)
> >>>    {
> >>> -	return spi->chip_select;
> >>> +	return spi->chip_select[idx];
> >>>    }
> >>>
> >>>    static inline void spi_set_chipselect(struct spi_device *spi, u8
> >>> idx, u8
> >> chipselect)
> >>>    {
> >>> -	spi->chip_select = chipselect;
> >>> +	spi->chip_select[idx] = chipselect;
> >>>    }
> >>>
> >>>    static inline struct gpio_desc *spi_get_csgpiod(const struct
> >>> spi_device *spi,
> >> u8 idx)
> >>>    {
> >>> -	return spi->cs_gpiod;
> >>> +	return spi->cs_gpiod[idx];
> >>>    }
> >>>
> >>>    static inline void spi_set_csgpiod(struct spi_device *spi, u8
> >>> idx, struct
> >> gpio_desc *csgpiod)
> >>>    {
> >>> -	spi->cs_gpiod = csgpiod;
> >>> +	spi->cs_gpiod[idx] = csgpiod;
> >>> +}
> >>> +
> >>> +static inline bool spi_is_csgpiod(struct spi_device *spi) {
> >>> +	u8 idx;
> >>> +
> >>> +	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
> >>> +		if (spi_get_csgpiod(spi, idx))
> >>> +			return true;
> >>> +	}
> >>> +	return false;
> >>>    }
> >>>
> >>>    /**
> >>> @@ -399,6 +422,8 @@ extern struct spi_device
> >> *spi_new_ancillary_device(struct spi_device *spi, u8 ch
> >>>     * @bus_lock_spinlock: spinlock for SPI bus locking
> >>>     * @bus_lock_mutex: mutex for exclusion of multiple callers
> >>>     * @bus_lock_flag: indicates that the SPI bus is locked for
> >>> exclusive use
> >>> + * @multi_cs_cap: indicates that the SPI Controller can assert/de-assert
> >>> + *	more than one chip select at once.
> >>>     * @setup: updates the device mode and clocking records used by a
> >>>     *	device's SPI controller; protocol code may call this.  This
> >>>     *	must fail if an unrecognized or unsupported mode is requested.
> >>> @@ -567,6 +592,11 @@ struct spi_controller {
> >>>    #define SPI_CONTROLLER_MUST_TX		BIT(4)	/* Requires tx
> */
> >>>    #define SPI_CONTROLLER_GPIO_SS		BIT(5)	/* GPIO CS
> must
> >> select slave */
> >>>    #define SPI_CONTROLLER_SUSPENDED	BIT(6)	/* Currently
> >> suspended */
> >>> +	/*
> >>> +	 * The spi-controller has multi chip select capability and can
> >>> +	 * assert/de-assert more than one chip select at once.
> >>> +	 */
> >>> +#define SPI_CONTROLLER_MULTI_CS		BIT(7)
> >>>
> >>>    	/* Flag indicating if the allocation of this struct is devres-managed */
> >>>    	bool			devm_allocated;
> >>> @@ -677,7 +707,8 @@ struct spi_controller {
> >>>    	bool				rt;
> >>>    	bool				auto_runtime_pm;
> >>>    	bool				cur_msg_mapped;
> >>> -	char				last_cs;
> >>> +	char				last_cs[SPI_CS_CNT_MAX];
> >>> +	char				last_cs_index_mask;
> >>>    	bool				last_cs_mode_high;
> >>>    	bool                            fallback;
> >>>    	struct completion               xfer_completion;