RE: [PATCH v2 1/2] mtd: fsl-quadspi: Update slave device hwcap based on mode provided in dtsi file

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Hi Cyrille,

> -----Original Message-----
> From: Cyrille Pitchen [mailto:cyrille.pitchen@xxxxxxxxxx]
> Sent: Tuesday, February 06, 2018 2:19 AM
> To: Yogesh Narayan Gaur <yogeshnarayan.gaur@xxxxxxx>; linux-
> mtd@xxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; robh@xxxxxxxxxx;
> mark.rutland@xxxxxxx; shawnguo@xxxxxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; boris.brezillon@xxxxxxxxxxxxxxxxxx;
> computersforpeace@xxxxxxxxx; Han Xu <han.xu@xxxxxxx>;
> festevam@xxxxxxxxx; Prabhakar Kushwaha <prabhakar.kushwaha@xxxxxxx>;
> Suresh Gupta <suresh.gupta@xxxxxxx>
> Subject: Re: [PATCH v2 1/2] mtd: fsl-quadspi: Update slave device hwcap based
> on mode provided in dtsi file
> 
> Hi Yogesh,
> 
> Le 02/02/2018 à 06:31, Yogesh Gaur a écrit :
> > FSL QuadSPI controller supports Single, dual, quad modes of operation.
> > Mode information is available via "spi-tx-bus-width" and
> > "spi-rx-bus-width" nodes of device tree for the connected slave device.
> >
> > Update read and write hwcap capability for slave device by reading
> > "spi-rx-bus-width" and "spi-tx-bus-width" respectively.
> > Assign hwcaps mask to minimal caps for the slave node i.e.
> > 	SNOR_HWCAPS_READ | SNOR_HWCAPS_PP
> >
> > If value not provided in device tree file, then fallback to default
> > mode i.e. SNOR_HWCAPS_READ_1_1_4 and SNOR_HWCAPS_PP.
> >
> > Signed-off-by: Prabhakar Kushwaha <prabhakar.kushwaha@xxxxxxx>
> > Signed-off-by: Yogesh Gaur <yogeshnarayan.gaur@xxxxxxx>
> > ---
> > Changes for v2:
> > - None
> >
> >  drivers/mtd/spi-nor/fsl-quadspi.c | 56
> > +++++++++++++++++++++++++++++++++++----
> >  1 file changed, 51 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/mtd/spi-nor/fsl-quadspi.c
> > b/drivers/mtd/spi-nor/fsl-quadspi.c
> > index b9c5918..1503e0c 100644
> > --- a/drivers/mtd/spi-nor/fsl-quadspi.c
> > +++ b/drivers/mtd/spi-nor/fsl-quadspi.c
> > @@ -994,17 +994,14 @@ static void fsl_qspi_unprep(struct spi_nor *nor,
> > enum spi_nor_ops ops)
> >
> >  static int fsl_qspi_probe(struct platform_device *pdev)  {
> > -	const struct spi_nor_hwcaps hwcaps = {
> > -		.mask = SNOR_HWCAPS_READ_1_1_4 |
> > -			SNOR_HWCAPS_PP,
> > -	};
> > +	struct spi_nor_hwcaps hwcaps;
> >  	struct device_node *np = pdev->dev.of_node;
> >  	struct device *dev = &pdev->dev;
> >  	struct fsl_qspi *q;
> >  	struct resource *res;
> >  	struct spi_nor *nor;
> >  	struct mtd_info *mtd;
> > -	int ret, i = 0;
> > +	int ret, i = 0, value;
> >
> >  	q = devm_kzalloc(dev, sizeof(*q), GFP_KERNEL);
> >  	if (!q)
> > @@ -1077,6 +1074,10 @@ static int fsl_qspi_probe(struct
> > platform_device *pdev)
> >
> >  	/* iterate the subnodes. */
> >  	for_each_available_child_of_node(dev->of_node, np) {
> > +		/* Reset hwcaps mask to minimal caps for the slave node. */
> > +		hwcaps.mask = SNOR_HWCAPS_READ | SNOR_HWCAPS_PP;
> > +		value = 0;
> > +
> >  		/* skip the holes */
> >  		if (!q->has_second_chip)
> >  			i *= 2;
> > @@ -1106,6 +1107,51 @@ static int fsl_qspi_probe(struct platform_device
> *pdev)
> >  		/* set the chip address for READID */
> >  		fsl_qspi_set_base_addr(q, nor);
> >
> > +		/*
> > +		 * If spi-rx-bus-width and spi-tx-bus-width not defined assign
> > +		 * default hardware capabilities SNOR_HWCAPS_READ_1_1_4
> and
> > +		 * SNOR_HWCAPS_PP supported by the Quad-SPI controller.
> > +		 */
> > +		if (!of_property_read_u32(np, "spi-rx-bus-width", &value)) {
> > +			switch (value) {
> > +			case 1:
> > +				hwcaps.mask |= SNOR_HWCAPS_READ |
> > +					       SNOR_HWCAPS_READ_FAST;
> > +				break;
> > +			case 2:
> > +				hwcaps.mask |= SNOR_HWCAPS_READ_1_1_2
> |
> > +					       SNOR_HWCAPS_READ_1_2_2;
> 
> I guess there is a misunderstanding in the meaning of spi-rx-bus-width and spi-
> tx-bus_width.
> 
> spi-rx-bus-width = <N>, resp. spi-tx-bus-width = <N>, means the SPI controller
> can receive, resp. send, data on N I/O Lines.
> 
> Then let's take the example of some Fast Read X-Y-Z command:
> 
> the op code is *sent* on X I/O lines: you need to check spi-tx-bus-width the
> address/mode/dummy bits are *sent* on Y I/O lines: check spi-tx-bus-width too
> the data bits are *received* on Z I/O lines: check spi-rx-bus_width.
> 
> > +				break;
> > +			case 4:
> > +				hwcaps.mask |= SNOR_HWCAPS_READ_1_1_4
> |
> > +					       SNOR_HWCAPS_READ_1_4_4;
> 
> The same here: to allow SPI 1-4-4, you have to check that spi-tx-bus-width == 4.
> 
> So your usage of spi-{tx|rx}-bus-width is not consistent with the usage done in
> the SPI subsystem. Please have a look at drivers/mtd/devices/m25p80.c,
> especially how the SPI_RX_QUAD and SPI_TX_QUAD flags are used in the
> m25p_probe() function to have a better idea of how it should work.
> 
> Also have a look at of_spi_parse_dt() in drivers/spi/spi.c, to figure out how the
> SPI_{TX|RX}_{DUAL|QUAD} flags are set according to the spi-{tx|rx}-bus-width
> DT properties.
> 
Thanks for review, would incorporate your review comments and would have usage of spi-{rx/tx}-bus-width as being done in SPI subsystem.

> > +				break;
> > +			default:
> > +				dev_err(dev,
> > +					"spi-rx-bus-width %d not supported\n",
> > +					value);
> > +				break;
> > +			}
> > +		} else
> > +			hwcaps.mask |= SNOR_HWCAPS_READ_1_1_4;
> 
> Not sure whether it passes checkpatch, you may have to add { } for the else
> statement even if there is a single line as the if statement use { }.
> 
I have run ' ./scripts/checkpatch.pl' present in linux-mtd code base and it hasn't reported any warning or error messages.
Meanwhile, would add {} braces for this else statement also.

--
Regards
Yogesh Gaur.

> Personally I don't mind that much. Please just check that your patch passes
> checkpatch verification and it will be okay for me :)
> 
> Best regards,
> 
> Cyrille
> 
> > +
> > +		if (!of_property_read_u32(np, "spi-tx-bus-width", &value)) {
> > +			switch (value) {
> > +			case 1:
> > +				hwcaps.mask |= SNOR_HWCAPS_PP;
> > +				break;
> > +			case 4:
> > +				hwcaps.mask |= SNOR_HWCAPS_PP_1_1_4 |
> > +					       SNOR_HWCAPS_PP_1_4_4;
> > +				break;
> > +			default:
> > +				dev_err(dev,
> > +					"spi-tx-bus-width %d not supported\n",
> > +					value);
> > +				break;
> > +			}
> > +		}
> > +
> >  		ret = spi_nor_scan(nor, NULL, &hwcaps);
> >  		if (ret)
> >  			goto mutex_failed;
> >

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