mmc: sdhci-of-arasan: Add quirk for unstable clocks

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 known to be 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>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/sdhci-of-arasan.c b/drivers/mmc/host/sdhci-of-arasan.c
index e3332a5..a40bcc2 100644 (file)
--- 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;
@@ -758,6 +771,9 @@ 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,