Re: [PATCH v2] mmc: sdhci: make sure SDHCI_CLOCK_CARD_EN bit sticks

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

On Wed, 19 Feb 2020 at 22:07, Jean-Francois Dagenais
<jeff.dagenais@gmail.com> wrote:
>
> Regardless of the broken-cd quirk, when it silently doesn't stick,
> no clock is applied to the bus lines, yet the code continues to
> try to make CMDs and times out after 10 seconds for each. This
> process can take up to a minute as mmc_rescan_try_freq tries the
> different commands to discover the card.
>
> Short of changing sdhci_enable_clk's signature chain in all
> dependent drivers, at least provide a hint that this might be the
> problem. This will save tons of time for system integrators.
>
> Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>

The change looks reasonable to me. However I would like to get an ack
by Adrian before applying, as I may not have thought of all the
consequences this change may have.

Kind regards
Uffe


> ---
> Changes in v2:
>  * removed redundant wmb()
> ---
>  drivers/mmc/host/sdhci.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 63db84481dff..42a02d034fda 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1894,6 +1894,20 @@ void sdhci_enable_clk(struct sdhci_host *host, u16 clk)
>
>         clk |= SDHCI_CLOCK_CARD_EN;
>         sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> +
> +       clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> +       if (clk & SDHCI_CLOCK_CARD_EN)
> +               return;
> +
> +       /* The controller will clear this bit if card absent condition is
> +        * detected. If card is indeed present, check platform configuration for
> +        * how CD is reported to the SDHCI host controller. There may be an
> +        * "assume present" mechanism in the platform registers, or your pin mux
> +        * may be incorrect.
> +        */
> +       pr_err("%s: SDHCI_CLOCK_CARD_EN bit did not stick. Card absent?\n",
> +               mmc_hostname(host->mmc));
> +       sdhci_dumpregs(host);
>  }
>  EXPORT_SYMBOL_GPL(sdhci_enable_clk);
>
> --
> 2.25.0
>