phy: rockchip-emmc: Wait even longer for the DLL to lock

Two times out of 2000 reboots I ran into the error message
"rockchip_emmc_phy_power: dllrdy timeout".  Presumably there is some
corner case where the DLL just takes a little longer to timeout.  Let's
give it even more time to handle these corner cases.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

1 files changed, 11 insertions, 1 deletions

diff --git a/drivers/phy/phy-rockchip-emmc.c b/drivers/phy/phy-rockchip-emmc.c
index a2aa6aca7dec..fd57345ffed2 100644
--- a/drivers/phy/phy-rockchip-emmc.c
+++ b/drivers/phy/phy-rockchip-emmc.c
@@ -206,8 +206,18 @@ static int rockchip_emmc_phy_power(struct phy *phy, bool on_off)
          * per the math: 10.2 us * (50000000 Hz / 100000 Hz) => 5.1 ms
          * Hopefully we won't be running at 100 kHz, but we should still make
          * sure we wait long enough.
+         *
+         * NOTE: There appear to be corner cases where the DLL seems to take
+         * extra long to lock for reasons that aren't understood.  In some
+         * extreme cases we've seen it take up to over 10ms (!).  We'll be
+         * generous and give it 50ms.  We still busy wait here because:
+         * - In most cases it should be super fast.
+         * - This is not called lots during normal operation so it shouldn't
+         *   be a power or performance problem to busy wait.  We expect it
+         *   only at boot / resume.  In both cases, eMMC is probably on the
+         *   critical path so busy waiting a little extra time should be OK.
          */
-        timeout = jiffies + msecs_to_jiffies(10);
+        timeout = jiffies + msecs_to_jiffies(50);
         do {
                 udelay(1);