Re: [PATCH 4/4] mmc: sdhci-acpi: Fix voltage switch for some Intel host controllers

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

On 19 October 2017 at 12:41, Adrian Hunter <adrian.hunter@intel.com> wrote:
> Some Intel host controllers use an ACPI device-specific method to ensure
> correct voltage switching. Fix voltage switch for those, by adding a call
> to the DSM.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
>  drivers/mmc/host/sdhci-acpi.c | 108 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 108 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-acpi.c b/drivers/mmc/host/sdhci-acpi.c
> index 5bb5880403b2..b988997a1e80 100644
> --- a/drivers/mmc/host/sdhci-acpi.c
> +++ b/drivers/mmc/host/sdhci-acpi.c
> @@ -96,6 +96,105 @@ static inline bool sdhci_acpi_flag(struct sdhci_acpi_host *c, unsigned int flag)
>         return c->slot && (c->slot->flags & flag);
>  }
>
> +enum {
> +       INTEL_DSM_FNS           =  0,
> +       INTEL_DSM_V18_SWITCH    =  3,
> +       INTEL_DSM_V33_SWITCH    =  4,
> +};
> +
> +struct intel_host {
> +       u32     dsm_fns;
> +};
> +
> +static const guid_t intel_dsm_guid =
> +       GUID_INIT(0xF6C13EA5, 0x65CD, 0x461F,
> +                 0xAB, 0x7A, 0x29, 0xF7, 0xE8, 0xD5, 0xBD, 0x61);
> +
> +static int __intel_dsm(struct intel_host *intel_host, struct device *dev,
> +                      unsigned int fn, u32 *result)
> +{
> +       union acpi_object *obj;
> +       int err = 0;
> +
> +       obj = acpi_evaluate_dsm(ACPI_HANDLE(dev), &intel_dsm_guid, 0, fn, NULL);
> +       if (!obj)
> +               return -EOPNOTSUPP;
> +
> +       if (obj->type == ACPI_TYPE_INTEGER) {
> +               *result = obj->integer.value;
> +       } else if (obj->type == ACPI_TYPE_BUFFER && obj->buffer.length > 0) {
> +               size_t len = min_t(size_t, obj->buffer.length, 4);
> +
> +               *result = 0;
> +               memcpy(result, obj->buffer.pointer, len);
> +       } else {
> +               dev_err(dev, "%s DSM fn %u obj->type %d obj->buffer.length %d\n",
> +                       __func__, fn, obj->type, obj->buffer.length);
> +               err = -EINVAL;
> +       }
> +

This hole ACPI thing looks weird. Could perhaps the ACPI core, model
this a vqmmc regulator instead?

That would keep the ACPI specific part closer to ACPI and we can treat
this similar to other mmc host drivers.

> +       ACPI_FREE(obj);
> +
> +       return err;
> +}
> +

[...]

Kind regards
Uffe