Re: [PATCHv3 1/2] spi: imx: fix use of native chip-selects with devicetree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi Oleksij,

On 20/07/17 16:34, Oleksij Rempel wrote:
Hi Greg,

On Tue, Jul 18, 2017 at 09:53:58PM -0300, Fabio Estevam wrote:
Adding Pengutronix folks on Cc.

On Tue, Jul 11, 2017 at 1:22 AM, Greg Ungerer <gerg@xxxxxxxxxxxxxx> wrote:
The commonly used mechanism of specifying the hardware or native
chip-select on an SPI device in devicetree (that is "cs-gpios = <0>")
does not result in the native chip-select being configured for use.
So external SPI devices that require use of the native chip-select
will not work.

You can successfully specify native chip-selects if using a platform
setup by specifying the cs-gpio as negative offset by 32. And that
works correctly. You cannot use the same method in devicetree.

The logic in the spi-imx.c driver during probe uses core spi function
of_spi_register_master() in spi.c to parse the "cs-gpios" devicetree tag.
For valid GPIO values that will be recorded for use, all other entries in
the cs_gpios list will be set to -ENOENT. So entries like "<0>" will be
set to -ENOENT in the cs_gpios list.

When the SPI device registers are setup the code will use the GPIO
listed in the cs_gpios list for the desired chip-select. If the cs_gpio
is less then 0 then it is intended to be for a native chip-select, and
its cs_gpio value is added to 32 to get the chipselect number to use.
Problem is that with devicetree this can only ever be -ENOENT (which
is -2), and that alone results in an invalid chip-select number. But also
doesn't allow selection of the native chip-select at all.

To fix, if the cs_gpio specified for this spi device is not a
valid GPIO then use the "chip_select" (that is the native chip-select
number) for hardware setup.

Signed-off-by: Greg Ungerer <gerg@xxxxxxxxxxxxxx>
---
  drivers/spi/spi-imx.c | 8 ++++----
  1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index b402530..f4fe66c 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -524,8 +524,8 @@ static int mx31_config(struct spi_device *spi, struct spi_imx_config *config)
                 reg |= MX31_CSPICTRL_POL;
         if (spi->mode & SPI_CS_HIGH)
                 reg |= MX31_CSPICTRL_SSPOL;
-       if (spi->cs_gpio < 0)
-               reg |= (spi->cs_gpio + 32) <<
+       if (!gpio_is_valid(spi->cs_gpio))
+               reg |= (spi->chip_select) <<
                         (is_imx35_cspi(spi_imx) ? MX35_CSPICTRL_CS_SHIFT :
                                                   MX31_CSPICTRL_CS_SHIFT);

@@ -616,8 +616,8 @@ static int mx21_config(struct spi_device *spi, struct spi_imx_config *config)
                 reg |= MX21_CSPICTRL_POL;
         if (spi->mode & SPI_CS_HIGH)
                 reg |= MX21_CSPICTRL_SSPOL;
-       if (spi->cs_gpio < 0)
-               reg |= (spi->cs_gpio + 32) << MX21_CSPICTRL_CS_SHIFT;
+       if (!gpio_is_valid(spi->cs_gpio))
+               reg |= spi->chip_select << MX21_CSPICTRL_CS_SHIFT;

         writel(reg, spi_imx->base + MXC_CSPICTRL);


hm... do I see this correctly, all native chip_selects should
be registered before gpio based CS?

I don't follow. The "<0>" must be in the position in the list where
you want to use the native chip select. You can't arbitrarily change
the order.


For example like this?
cs-gpios = <0>, <&gpio1 1 0>, <&gpio1 2 0>;

Looks like we don't have any sanity checks for this kind of
configuration:
cs-gpios = <&gpio1 1 0>, <&gpio1 2 0>, <0>;

The chip_select is sanity checked in spi_add_device().


We may shift some wired numbers here:
reg |= spi->chip_select << MX21_CSPICTRL_CS_SHIFT;

I am not sure I see how that can be the case?

Regards
Greg



this should be reflected in the documentation too:
Documentation/devicetree/bindings/spi/spi-bus.txt


--
To unsubscribe from this list: send the line "unsubscribe linux-spi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux Kernel]     [Linux ARM (vger)]     [Linux ARM MSM]     [Linux Omap]     [Linux Arm]     [Linux Tegra]     [Fedora ARM]     [Linux for Samsung SOC]     [eCos]     [Linux Fastboot]     [Gcc Help]     [Git]     [DCCP]     [IETF Announce]     [Security]     [Linux MIPS]     [Yosemite Campsites]

  Powered by Linux