[PATCH v2 2/4] mmc: sdhci-brcmstb: Enable Clock Gating to save power

[Ulf Hansson]

On Wed, 27 Apr 2022 at 20:09, Kamal Dasu <kdasu.kdev at gmail.com> wrote:
>
> From: Al Cooper <alcooperx at gmail.com>
>
> Enabling this feature will allow the controller to stop the bus
> clock when the bus is idle. The feature is not part of the standard
> and is unique to newer Arasan cores and is enabled with a bit in a
> vendor specific register. This feature will only be enabled for
> non-removable devices because they don't switch the voltage and
> clock gating breaks SD Card volatge switching.
>
> Signed-off-by: Al Cooper <alcooperx at gmail.com>
> Signed-off-by: Kamal Dasu <kdasu.kdev at gmail.com>
> Acked-by: Florian Fainelli <f.fainelli at gmail.com>
> Acked-by: Adrian Hunter <adrian.hunter at intel.com>

Applied for next, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/sdhci-brcmstb.c | 35 +++++++++++++++++++++++++++++++-
>  1 file changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-brcmstb.c b/drivers/mmc/host/sdhci-brcmstb.c
> index 244780481193..683d0c685748 100644
> --- a/drivers/mmc/host/sdhci-brcmstb.c
> +++ b/drivers/mmc/host/sdhci-brcmstb.c
> @@ -17,11 +17,14 @@
>
>  #define SDHCI_VENDOR 0x78
>  #define  SDHCI_VENDOR_ENHANCED_STRB 0x1
> +#define  SDHCI_VENDOR_GATE_SDCLK_EN 0x2
>
>  #define BRCMSTB_MATCH_FLAGS_NO_64BIT           BIT(0)
>  #define BRCMSTB_MATCH_FLAGS_BROKEN_TIMEOUT     BIT(1)
> +#define BRCMSTB_MATCH_FLAGS_HAS_CLOCK_GATE     BIT(2)
>
>  #define BRCMSTB_PRIV_FLAGS_HAS_CQE             BIT(0)
> +#define BRCMSTB_PRIV_FLAGS_GATE_CLOCK          BIT(1)
>
>  #define SDHCI_ARASAN_CQE_BASE_ADDR             0x200
>
> @@ -36,6 +39,27 @@ struct brcmstb_match_priv {
>         const unsigned int flags;
>  };
>
> +static inline void enable_clock_gating(struct sdhci_host *host)
> +{
> +       u32 reg;
> +
> +       reg = sdhci_readl(host, SDHCI_VENDOR);
> +       reg |= SDHCI_VENDOR_GATE_SDCLK_EN;
> +       sdhci_writel(host, reg, SDHCI_VENDOR);
> +}
> +
> +void brcmstb_reset(struct sdhci_host *host, u8 mask)
> +{
> +       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +       struct sdhci_brcmstb_priv *priv = sdhci_pltfm_priv(pltfm_host);
> +
> +       sdhci_reset(host, mask);
> +
> +       /* Reset will clear this, so re-enable it */
> +       if (priv->flags & BRCMSTB_PRIV_FLAGS_GATE_CLOCK)
> +               enable_clock_gating(host);
> +}
> +
>  static void sdhci_brcmstb_hs400es(struct mmc_host *mmc, struct mmc_ios *ios)
>  {
>         struct sdhci_host *host = mmc_priv(mmc);
> @@ -131,7 +155,7 @@ static struct sdhci_ops sdhci_brcmstb_ops = {
>  static struct sdhci_ops sdhci_brcmstb_ops_7216 = {
>         .set_clock = sdhci_brcmstb_set_clock,
>         .set_bus_width = sdhci_set_bus_width,
> -       .reset = sdhci_reset,
> +       .reset = brcmstb_reset,
>         .set_uhs_signaling = sdhci_brcmstb_set_uhs_signaling,
>  };
>
> @@ -147,6 +171,7 @@ static struct brcmstb_match_priv match_priv_7445 = {
>  };
>
>  static const struct brcmstb_match_priv match_priv_7216 = {
> +       .flags = BRCMSTB_MATCH_FLAGS_HAS_CLOCK_GATE,
>         .hs400es = sdhci_brcmstb_hs400es,
>         .ops = &sdhci_brcmstb_ops_7216,
>  };
> @@ -273,6 +298,14 @@ static int sdhci_brcmstb_probe(struct platform_device *pdev)
>         if (res)
>                 goto err;
>
> +       /*
> +        * Automatic clock gating does not work for SD cards that may
> +        * voltage switch so only enable it for non-removable devices.
> +        */
> +       if ((match_priv->flags & BRCMSTB_MATCH_FLAGS_HAS_CLOCK_GATE) &&
> +           (host->mmc->caps & MMC_CAP_NONREMOVABLE))
> +               priv->flags |= BRCMSTB_PRIV_FLAGS_GATE_CLOCK;
> +
>         /*
>          * If the chip has enhanced strobe and it's enabled, add
>          * callback
> --
> 2.17.1
>