Re: [RFC PATCH 2/2] mmc: allow to match the device tree to apply quirks

[Ulf Hansson <ulf.hansson@linaro.org>]

On Thu, 14 Oct 2021 at 16:30, Jerome Pouiller
<Jerome.Pouiller@silabs.com> wrote:
>
> From: Jérôme Pouiller <jerome.pouiller@silabs.com>
>
> MMC subsystem provides a way to apply quirks when a device match some
> properties (VID, PID, etc...) Unfortunately, some SDIO devices does not
> comply with the SDIO specification and does not provide reliable VID/PID
> (eg. Silabs WF200).
>
> So, the drivers for these devices rely on device tree to identify the
> device.
>
> This patch allows the MMC to also rely on the device tree to apply a
> quirk.
>
> Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
> ---
>  drivers/mmc/core/card.h   |  3 +++
>  drivers/mmc/core/quirks.h | 18 ++++++++++++++++++
>  2 files changed, 21 insertions(+)
>
> diff --git a/drivers/mmc/core/card.h b/drivers/mmc/core/card.h
> index 7bd392d55cfa..2f73f8567e14 100644
> --- a/drivers/mmc/core/card.h
> +++ b/drivers/mmc/core/card.h
> @@ -59,6 +59,9 @@ struct mmc_fixup {
>         /* for MMC cards */
>         unsigned int ext_csd_rev;
>
> +       /* Match against functions declared in device tree */
> +       const char *const *of_compatible;

const char is probably sufficient.

> +
>         void (*vendor_fixup)(struct mmc_card *card, int data);
>         int data;
>  };
> diff --git a/drivers/mmc/core/quirks.h b/drivers/mmc/core/quirks.h
> index c7ef2d14b359..ef368386e711 100644
> --- a/drivers/mmc/core/quirks.h
> +++ b/drivers/mmc/core/quirks.h
> @@ -10,6 +10,7 @@
>   *
>   */
>
> +#include <linux/of.h>
>  #include <linux/mmc/sdio_ids.h>
>
>  #include "card.h"
> @@ -145,6 +146,20 @@ static const struct mmc_fixup __maybe_unused sdio_fixup_methods[] = {
>         END_FIXUP
>  };
>
> +static inline bool mmc_fixup_of_compatible_match(struct mmc_card *card,
> +                                                const char *const *compat_list)
> +{
> +       struct device_node *of_node;
> +       int i;
> +
> +       for (i = 0; i < 7; i++) {

We need to iterate up '8', to cover all functional devices.

The function numbers are from 1->7, while we use '0' for the
"mmc-card" compatible.

> +               of_node = mmc_of_find_child_device(card->host, i);
> +               if (of_node && of_device_compatible_match(of_node, compat_list))
> +                       return true;
> +       }

Another option, which would avoid doing the iteration over and over
again in mmc_of_find_child_device(), would be to simply do the parsing
of the compatible in the child nodes, right here. In other words, just
use for_each_child_of_node().

> +       return false;
> +}
> +
>  static inline void mmc_fixup_device(struct mmc_card *card,
>                                     const struct mmc_fixup *table)
>  {
> @@ -173,6 +188,9 @@ static inline void mmc_fixup_device(struct mmc_card *card,
>                         continue;
>                 if (rev < f->rev_start || rev > f->rev_end)
>                         continue;
> +               if (f->of_compatible != NULL &&
> +                   !mmc_fixup_of_compatible_match(card, f->of_compatible))
> +                       continue;
>
>                 dev_dbg(&card->dev, "calling %ps\n", f->vendor_fixup);
>                 f->vendor_fixup(card, f->data);

Kind regards
Uffe