Re: [PATCH 2/2] mmc: sdhci-of-at91: add DT property to enable calibration on full reset

Ludovic Desroches
2019-10-11T12:41:24Z

On Tue, Oct 08, 2019 at 02:34:32PM +0200, Nicolas Ferre wrote:
> Add a property to keep the analog calibration cell powered.
> This feature is specific to the Microchip SDHCI IP and outside
> of the standard SDHCI register map.
>
> By always keeping it on, after a full reset sequence, we make sure
> that this feature is activated and not disabled.
>
> We expose a hardware property to the DT as this feature can be used
> to adapt SDHCI behavior vs. how the SDCAL SoC pin is connected
> on the board.
>
> Note that managing properly this property would reduce
> power consumption on some SAMA5D2 SiP revisions.
>
> Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>

Thanks

Ludovic

> ---
> drivers/mmc/host/sdhci-of-at91.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
> index e7d1920729fb..9571c4a882a9 100644
> --- a/drivers/mmc/host/sdhci-of-at91.c
> +++ b/drivers/mmc/host/sdhci-of-at91.c
> @@ -27,6 +27,9 @@
> #define SDMMC_CACR 0x230
> #define SDMMC_CACR_CAPWREN BIT(0)
> #define SDMMC_CACR_KEY (0x46 << 8)
> +#define SDMMC_CALCR 0x240
> +#define SDMMC_CALCR_EN BIT(0)
> +#define SDMMC_CALCR_ALWYSON BIT(4)
>
> #define SDHCI_AT91_PRESET_COMMON_CONF 0x400 /* drv type B, programmable clock mode */
>
> @@ -35,6 +38,7 @@ struct sdhci_at91_priv {
> struct clk *gck;
> struct clk *mainck;
> bool restore_needed;
> + bool cal_always_on;
> };
>
> static void sdhci_at91_set_force_card_detect(struct sdhci_host *host)
> @@ -116,10 +120,17 @@ static void sdhci_at91_set_uhs_signaling(struct sdhci_host *host,
>
> static void sdhci_at91_reset(struct sdhci_host *host, u8 mask)
> {
> + struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> + struct sdhci_at91_priv *priv = sdhci_pltfm_priv(pltfm_host);
> +
> sdhci_reset(host, mask);
>
> if (host->mmc->caps & MMC_CAP_NONREMOVABLE)
> sdhci_at91_set_force_card_detect(host);
> +
> + if (priv->cal_always_on && (mask & SDHCI_RESET_ALL))
> + sdhci_writel(host, SDMMC_CALCR_ALWYSON | SDMMC_CALCR_EN,
> + SDMMC_CALCR);
> }
>
> static const struct sdhci_ops sdhci_at91_sama5d2_ops = {
> @@ -345,6 +356,14 @@ static int sdhci_at91_probe(struct platform_device *pdev)
>
> priv->restore_needed = false;
>
> + /*
> + * if SDCAL pin is wrongly connected, we must enable
> + * the analog calibration cell permanently.
> + */
> + priv->cal_always_on =
> + device_property_read_bool(&pdev->dev,
> + "microchip,sdcal-inverted");
> +
> ret = mmc_of_parse(host->mmc);
> if (ret)
> goto clocks_disable_unprepare;
> --
> 2.17.1
>