[PATCH] spi: bcm2835: fix gpio cs level inversion

[PATCH] spi: bcm2835: fix gpio cs level inversion

[Martin Hundebøll]

The work on improving gpio chip-select in spi core, and the following
fixes, has caused the bcm2835 spi driver to use wrong levels. Fix this
by simply removing level handling in the bcm2835 driver, and let the
core do its work.

Fixes: 3e5ec1db8bfe ("spi: Fix SPI_CS_HIGH setting when using native and GPIO CS")
Cc: <stable@vger.kernel.org>
Signed-off-by: Martin Hundebøll <martin@geanix.com>
---
 drivers/spi/spi-bcm2835.c | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index b87116e9b413..9b6ba94fe878 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -1259,18 +1259,6 @@ static int bcm2835_spi_setup(struct spi_device *spi)
 	if (!chip)
 		return 0;
 
-	/*
-	 * Retrieve the corresponding GPIO line used for CS.
-	 * The inversion semantics will be handled by the GPIO core
-	 * code, so we pass GPIOD_OUT_LOW for "unasserted" and
-	 * the correct flag for inversion semantics. The SPI_CS_HIGH
-	 * on spi->mode cannot be checked for polarity in this case
-	 * as the flag use_gpio_descriptors enforces SPI_CS_HIGH.
-	 */
-	if (of_property_read_bool(spi->dev.of_node, "spi-cs-high"))
-		lflags = GPIO_ACTIVE_HIGH;
-	else
-		lflags = GPIO_ACTIVE_LOW;
 	spi->cs_gpiod = gpiochip_request_own_desc(chip, 8 - spi->chip_select,
 						  DRV_NAME,
 						  lflags,
-- 
2.28.0

Re: [PATCH] spi: bcm2835: fix gpio cs level inversion

[Nathan Chancellor]

On Wed, Oct 14, 2020 at 11:02:30AM +0200, Martin Hundebøll wrote:
> The work on improving gpio chip-select in spi core, and the following
> fixes, has caused the bcm2835 spi driver to use wrong levels. Fix this
> by simply removing level handling in the bcm2835 driver, and let the
> core do its work.
> 
> Fixes: 3e5ec1db8bfe ("spi: Fix SPI_CS_HIGH setting when using native and GPIO CS")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Martin Hundebøll <martin@geanix.com>
> ---
>  drivers/spi/spi-bcm2835.c | 12 ------------
>  1 file changed, 12 deletions(-)
> 
> diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
> index b87116e9b413..9b6ba94fe878 100644
> --- a/drivers/spi/spi-bcm2835.c
> +++ b/drivers/spi/spi-bcm2835.c
> @@ -1259,18 +1259,6 @@ static int bcm2835_spi_setup(struct spi_device *spi)
>  	if (!chip)
>  		return 0;
>  
> -	/*
> -	 * Retrieve the corresponding GPIO line used for CS.
> -	 * The inversion semantics will be handled by the GPIO core
> -	 * code, so we pass GPIOD_OUT_LOW for "unasserted" and
> -	 * the correct flag for inversion semantics. The SPI_CS_HIGH
> -	 * on spi->mode cannot be checked for polarity in this case
> -	 * as the flag use_gpio_descriptors enforces SPI_CS_HIGH.
> -	 */
> -	if (of_property_read_bool(spi->dev.of_node, "spi-cs-high"))
> -		lflags = GPIO_ACTIVE_HIGH;
> -	else
> -		lflags = GPIO_ACTIVE_LOW;
>  	spi->cs_gpiod = gpiochip_request_own_desc(chip, 8 - spi->chip_select,
>  						  DRV_NAME,
>  						  lflags,
> -- 
> 2.28.0
> 
> 

Clang now warns:

drivers/spi/spi-bcm2835.c:1264:9: warning: variable 'lflags' is uninitialized when used here [-Wuninitialized]
                                                  lflags,
                                                  ^~~~~~
drivers/spi/spi-bcm2835.c:1196:2: note: variable 'lflags' is declared here
        enum gpio_lookup_flags lflags;
        ^
1 warning generated.

Cheers,
Nathan

[PATCH] spi: bcm2835: remove use of uninitialized gpio flags variable

[Martin Hundebøll]

Removing the duplicate gpio chip select level handling in
bcm2835_spi_setup() left the lflags variable uninitialized. Avoid trhe
use of such variable by passing default flags to
gpiochip_request_own_desc().

Fixes: 5e31ba0c0543 ("spi: bcm2835: fix gpio cs level inversion")
Signed-off-by: Martin Hundebøll <martin@geanix.com>
---

Feel free to squash this commit with my previous patch, if rebasing
for-next is allowed.

 drivers/spi/spi-bcm2835.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index 9b6ba94fe878..7104cf17b848 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -1193,7 +1193,6 @@ static int bcm2835_spi_setup(struct spi_device *spi)
 	struct spi_controller *ctlr = spi->controller;
 	struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
 	struct gpio_chip *chip;
-	enum gpio_lookup_flags lflags;
 	u32 cs;
 
 	/*
@@ -1261,7 +1260,7 @@ static int bcm2835_spi_setup(struct spi_device *spi)
 
 	spi->cs_gpiod = gpiochip_request_own_desc(chip, 8 - spi->chip_select,
 						  DRV_NAME,
-						  lflags,
+						  GPIO_LOOKUP_FLAGS_DEFAULT,
 						  GPIOD_OUT_LOW);
 	if (IS_ERR(spi->cs_gpiod))
 		return PTR_ERR(spi->cs_gpiod);
-- 
2.28.0

Re: [PATCH] spi: bcm2835: remove use of uninitialized gpio flags variable

[Mark Brown]

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On Thu, Nov 05, 2020 at 10:06:15AM +0100, Martin Hundebøll wrote:
> Removing the duplicate gpio chip select level handling in
> bcm2835_spi_setup() left the lflags variable uninitialized. Avoid trhe
> use of such variable by passing default flags to
> gpiochip_request_own_desc().

Please don't send patches in reply to old threads, it buries them and
can make it unclear what is a new patch which needs review.  Send new
patches as new threads.

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