Re: [PATCH v2] mmc: sdhci-of-arasan: Add quirk for unstable clocks

Adrian Hunter
2018-06-19T09:09:17Z

On 15/06/18 11:18, Helmut Grohne wrote:
> Some controllers immediately report SDHCI_CLOCK_INT_STABLE after
> enabling the clock even when the clock is not stable. When used in
> conjunction with older/slower cards, this can result in:
>
> mmc0: error -84 whilst initialising SD card
>
> When the stable reporting is broken, we simply wait for the maximum
> stabilization period.
>
> Signed-off-by: Helmut Grohne <h.grohne@intenta.de>

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
> Documentation/devicetree/bindings/mmc/arasan,sdhci.txt | 2 ++
> drivers/mmc/host/sdhci-of-arasan.c | 16 ++++++++++++++++
> 2 files changed, 18 insertions(+)
>
> Changes since v1 (RFC):
> * Use an arasan-specific quirk in the ->set_clock() callback as requested by
> Adrian Hunter.
>
> diff --git a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
> index 60481bfc3d31..c0e0f04a8504 100644
> --- a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
> +++ b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
> @@ -39,6 +39,8 @@ Optional Properties:
> - xlnx,fails-without-test-cd: when present, the controller doesn't work when
> the CD line is not connected properly, and the line is not connected
> properly. Test mode can be used to force the controller to function.
> + - xlnx,int-clock-stable-broken: when present, the controller always reports
> + that the internal clock is stable even when it is not.
>
> Example:
> sdhci@e0100000 {
> diff --git a/drivers/mmc/host/sdhci-of-arasan.c b/drivers/mmc/host/sdhci-of-arasan.c
> index c33a5f7393bd..f7fe26c75150 100644
> --- a/drivers/mmc/host/sdhci-of-arasan.c
> +++ b/drivers/mmc/host/sdhci-of-arasan.c
> @@ -102,6 +102,9 @@ struct sdhci_arasan_data {
>
> /* Controller does not have CD wired and will not function normally without */
> #define SDHCI_ARASAN_QUIRK_FORCE_CDTEST BIT(0)
> +/* Controller immediately reports SDHCI_CLOCK_INT_STABLE after enabling the
> + * internal clock even when the clock isn't stable */
> +#define SDHCI_ARASAN_QUIRK_CLOCK_UNSTABLE BIT(1)
> };
>
> static const struct sdhci_arasan_soc_ctl_map rk3399_soc_ctl_map = {
> @@ -207,6 +210,16 @@ static void sdhci_arasan_set_clock(struct sdhci_host *host, unsigned int clock)
>
> sdhci_set_clock(host, clock);
>
> + if (sdhci_arasan->quirks & SDHCI_ARASAN_QUIRK_CLOCK_UNSTABLE)
> + /*
> + * Some controllers immediately report SDHCI_CLOCK_INT_STABLE
> + * after enabling the clock even though the clock is not
> + * stable. Trying to use a clock without waiting here results
> + * in EILSEQ while detecting some older/slower cards. The
> + * chosen delay is the maximum delay from sdhci_set_clock.
> + */
> + msleep(20);
> +
> if (ctrl_phy) {
> phy_power_on(sdhci_arasan->phy);
> sdhci_arasan->is_phy_on = true;
> @@ -759,6 +772,9 @@ static int sdhci_arasan_probe(struct platform_device *pdev)
> if (of_property_read_bool(np, "xlnx,fails-without-test-cd"))
> sdhci_arasan->quirks |= SDHCI_ARASAN_QUIRK_FORCE_CDTEST;
>
> + if (of_property_read_bool(np, "xlnx,int-clock-stable-broken"))
> + sdhci_arasan->quirks |= SDHCI_ARASAN_QUIRK_CLOCK_UNSTABLE;
> +
> pltfm_host->clk = clk_xin;
>
> if (of_device_is_compatible(pdev->dev.of_node,
>