linux-kernel - Re: [PATCH] spi: bcm2835: Restore native CS probing when pinctrl-bcm2835 is absent

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Message-ID: <CAMRc=MeiALzO3XAmH9BLjxrB3EA1br1tpzHd5Qucw2NCVQ2q7g@mail.gmail.com>
Date: Wed, 2 Apr 2025 13:44:04 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Florian Fainelli <florian.fainelli@...adcom.com>
Cc: linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>, 
	Ray Jui <rjui@...adcom.com>, Scott Branden <sbranden@...adcom.com>, 
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, 
	Linus Walleij <linus.walleij@...aro.org>, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, 
	"open list:SPI SUBSYSTEM" <linux-spi@...r.kernel.org>, 
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" <linux-rpi-kernel@...ts.infradead.org>, 
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] spi: bcm2835: Restore native CS probing when
 pinctrl-bcm2835 is absent

On Wed, Apr 2, 2025 at 1:37 AM Florian Fainelli
<florian.fainelli@...adcom.com> wrote:
>
> The lookup table forces the use of the "pinctrl-bcm2835" GPIO chip
> provider and essentially assumes that there is going to be such a
> provider, and if not, we will fail to set-up the SPI device.
>

Yeah, the consumer driver itself is an unfortunate place to define the
provider data. This could potentially be moved to gpiolib-of.c quirks.

> While this is true on Raspberry Pi based systems (2835/36/37, 2711,
> 2712), this is not true on 7712/77122 Broadcom STB systems which use the
> SPI driver, but not the GPIO driver.
>
> There used to be an early check:
>
>        chip = gpiochip_find("pinctrl-bcm2835", chip_match_name);
>        if (!chip)
>                return 0;
>
> which would accomplish that nicely, bring something similar back by
> checking for the compatible strings matched by the pinctrl-bcm2835.c
> driver, if there is no Device Tree node matching those compatible
> strings, then we won't find any GPIO provider registered by the
> "pinctrl-bcm2835" driver.
>
> Fixes: 21f252cd29f0 ("spi: bcm2835: reduce the abuse of the GPIO API")
> Signed-off-by: Florian Fainelli <florian.fainelli@...adcom.com>
> ---
>  drivers/spi/spi-bcm2835.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
> index a5d621b94d5e..5926e004d9a6 100644
> --- a/drivers/spi/spi-bcm2835.c
> +++ b/drivers/spi/spi-bcm2835.c
> @@ -1226,7 +1226,12 @@ static int bcm2835_spi_setup(struct spi_device *spi)
>         struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
>         struct bcm2835_spidev *target = spi_get_ctldata(spi);
>         struct gpiod_lookup_table *lookup __free(kfree) = NULL;
> -       int ret;
> +       const char *pinctrl_compats[] = {
> +               "brcm,bcm2835-gpio",
> +               "brcm,bcm2711-gpio",
> +               "brcm,bcm7211-gpio",
> +       };
> +       int ret, i;
>         u32 cs;
>
>         if (!target) {
> @@ -1291,6 +1296,14 @@ static int bcm2835_spi_setup(struct spi_device *spi)
>                 goto err_cleanup;
>         }
>
> +       for (i = 0; i < ARRAY_SIZE(pinctrl_compats); i++) {
> +               if (of_find_compatible_node(NULL, NULL, pinctrl_compats[i]))
> +                       break;
> +       }
> +
> +       if (i == ARRAY_SIZE(pinctrl_compats))
> +               return 0;
> +
>         /*
>          * TODO: The code below is a slightly better alternative to the utter
>          * abuse of the GPIO API that I found here before. It creates a
> --
> 2.34.1
>
>

The fix is good for now but I'd still try to move this out of the
driver at some point.

Acked-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>