linux-kernel - Re: [PATCH 1/2] mmc: xenon: fix PHY init clock stability

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Date: Wed, 7 Feb 2024 18:23:22 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Elad Nachman <enachman@...vell.com>
Cc: huziji@...vell.com, adrian.hunter@...el.com, linux-mmc@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mmc: xenon: fix PHY init clock stability

On Wed, 7 Feb 2024 at 18:04, Elad Nachman <enachman@...vell.com> wrote:
>
> From: Elad Nachman <enachman@...vell.com>
>
> Each time SD/mmc phy is initialized, at times, in some of
> the attempts, phy fails to completes its initialization
> which results into timeout error. Per the HW spec, it is
> a pre-requisite to ensure a stable SD clock before a phy
> initialization is attempted.
>
> Signed-off-by: Elad Nachman <enachman@...vell.com>
> ---
>  drivers/mmc/host/sdhci-xenon-phy.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-xenon-phy.c b/drivers/mmc/host/sdhci-xenon-phy.c
> index 8cf3a375de65..4e99197b62c3 100644
> --- a/drivers/mmc/host/sdhci-xenon-phy.c
> +++ b/drivers/mmc/host/sdhci-xenon-phy.c
> @@ -216,6 +216,24 @@ static int xenon_alloc_emmc_phy(struct sdhci_host *host)
>         return 0;
>  }
>
> +static int xenon_check_stability_internal_clk(struct sdhci_host *host)
> +{
> +       u32 reg;
> +       ktime_t timeout;
> +
> +       /* Wait max 20 ms */
> +       timeout = ktime_add_ms(ktime_get(), 20);
> +       while (!((reg = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
> +               & SDHCI_CLOCK_INT_STABLE)) {
> +               if (ktime_after(ktime_get(), timeout)) {
> +                       dev_err(mmc_dev(host->mmc), "phy_init: Internal clock never stabilized.\n");
> +                       return -ETIMEDOUT;
> +               }
> +               usleep_range(900, 1100);
> +       }
> +       return 0;

Please convert the above into readx_poll_timeout() or similar.

> +}
> +
>  /*
>   * eMMC 5.0/5.1 PHY init/re-init.
>   * eMMC PHY init should be executed after:
> @@ -232,6 +250,11 @@ static int xenon_emmc_phy_init(struct sdhci_host *host)
>         struct xenon_priv *priv = sdhci_pltfm_priv(pltfm_host);
>         struct xenon_emmc_phy_regs *phy_regs = priv->emmc_phy_regs;
>
> +       int ret = xenon_check_stability_internal_clk(host);
> +
> +       if (ret)
> +               return ret;
> +
>         reg = sdhci_readl(host, phy_regs->timing_adj);
>         reg |= XENON_PHY_INITIALIZAION;
>         sdhci_writel(host, reg, phy_regs->timing_adj);

Kind regards
Uffe