[PATCH V2 04/10] mmc: sdhci-iproc: Cap min clock frequency on BCM2711

[Ulf Hansson]

On Sat, 7 Aug 2021 at 13:07, Stefan Wahren <stefan.wahren at i2se.com> wrote:
>
> From: Nicolas Saenz Julienne <nsaenz at kernel.org>
>
> There is a known bug on BCM2711's SDHCI core integration where the
> controller will hang when the difference between the core clock and the
> bus clock is too great. Specifically this can be reproduced under the
> following conditions:
>
> - No SD card plugged in, polling thread is running, probing cards at
>   100 kHz.
> - BCM2711's core clock configured at 500MHz or more.
>
> So set 200 kHz as the minimum clock frequency available for that board.
>
> For more information on the issue see this:
> https://lore.kernel.org/linux-mmc/20210322185816.27582-1-nsaenz@kernel.org/T/#m11f2783a09b581da6b8a15f302625b43a6ecdeca
>
> Fixes: f84e411c85be ("mmc: sdhci-iproc: Add support for emmc2 of the BCM2711")
> Signed-off-by: Nicolas Saenz Julienne <nsaenz at kernel.org>
> Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>

Applied for fixes and by adding a stable tag, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/sdhci-iproc.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-iproc.c b/drivers/mmc/host/sdhci-iproc.c
> index cce390f..032bf85 100644
> --- a/drivers/mmc/host/sdhci-iproc.c
> +++ b/drivers/mmc/host/sdhci-iproc.c
> @@ -173,6 +173,23 @@ static unsigned int sdhci_iproc_get_max_clock(struct sdhci_host *host)
>                 return pltfm_host->clock;
>  }
>
> +/*
> + * There is a known bug on BCM2711's SDHCI core integration where the
> + * controller will hang when the difference between the core clock and the bus
> + * clock is too great. Specifically this can be reproduced under the following
> + * conditions:
> + *
> + *  - No SD card plugged in, polling thread is running, probing cards at
> + *    100 kHz.
> + *  - BCM2711's core clock configured at 500MHz or more
> + *
> + * So we set 200kHz as the minimum clock frequency available for that SoC.
> + */
> +static unsigned int sdhci_iproc_bcm2711_get_min_clock(struct sdhci_host *host)
> +{
> +       return 200000;
> +}
> +
>  static const struct sdhci_ops sdhci_iproc_ops = {
>         .set_clock = sdhci_set_clock,
>         .get_max_clock = sdhci_iproc_get_max_clock,
> @@ -271,6 +288,7 @@ static const struct sdhci_ops sdhci_iproc_bcm2711_ops = {
>         .set_clock = sdhci_set_clock,
>         .set_power = sdhci_set_power_and_bus_voltage,
>         .get_max_clock = sdhci_iproc_get_max_clock,
> +       .get_min_clock = sdhci_iproc_bcm2711_get_min_clock,
>         .set_bus_width = sdhci_set_bus_width,
>         .reset = sdhci_reset,
>         .set_uhs_signaling = sdhci_set_uhs_signaling,
> --
> 2.7.4
>