phy: rockchip-emmc: configure default output tap delay

The output tap delay controls helps maintain the hold requirements for
eMMC. The exact value is dependent on the SoC and other factors, though
it isn't really an exact science. But the default of 0 is not very good,
as it doesn't give the eMMC much hold time, so let's bump up to 4
(approx 90 degree phase?). If we need to configure this any further
(e.g., based on board or speed factors), we may need to consider a
device tree representation.

Suggested-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/phy/phy-rockchip-emmc.c b/drivers/phy/phy-rockchip-emmc.c
index f2f75cf69af1..a0b87cc6c818 100644
--- a/drivers/phy/phy-rockchip-emmc.c
+++ b/drivers/phy/phy-rockchip-emmc.c
@@ -69,6 +69,11 @@
 #define PHYCTRL_DR_66OHM        0x2
 #define PHYCTRL_DR_100OHM       0x3
 #define PHYCTRL_DR_40OHM        0x4
+#define PHYCTRL_OTAPDLYENA              0x1
+#define PHYCTRL_OTAPDLYENA_MASK         0x1
+#define PHYCTRL_OTAPDLYENA_SHIFT        0xb
+#define PHYCTRL_OTAPDLYSEL_MASK         0xf
+#define PHYCTRL_OTAPDLYSEL_SHIFT        0x7
 
 struct rockchip_emmc_phy {
         unsigned int    reg_offset;
@@ -181,6 +186,20 @@ static int rockchip_emmc_phy_power_on(struct phy *phy)
                                    PHYCTRL_DR_MASK,
                                    PHYCTRL_DR_SHIFT));
 
+        /* Output tap delay: enable */
+        regmap_write(rk_phy->reg_base,
+                     rk_phy->reg_offset + GRF_EMMCPHY_CON0,
+                     HIWORD_UPDATE(PHYCTRL_OTAPDLYENA,
+                                   PHYCTRL_OTAPDLYENA_MASK,
+                                   PHYCTRL_OTAPDLYENA_SHIFT));
+
+        /* Output tap delay */
+        regmap_write(rk_phy->reg_base,
+                     rk_phy->reg_offset + GRF_EMMCPHY_CON0,
+                     HIWORD_UPDATE(4,
+                                   PHYCTRL_OTAPDLYSEL_MASK,
+                                   PHYCTRL_OTAPDLYSEL_SHIFT));
+
         /* Power up emmc phy analog blocks */
         ret = rockchip_emmc_phy_power(rk_phy, PHYCTRL_PDB_PWR_ON);
         if (ret)