[PATCH v2 20/40] mmc: tegra: Add a workaround for tap value change glitch

[Aapo Vienamo]

Add quirk to disable the card clock during configuration of the tap
value in tegra_sdhci_set_tap() and issue sdhci_reset() after value
change. This is a workaround to avoid propagation of a potential
glitch caused by setting the tap value.

Signed-off-by: Aapo Vienamo <avien...@nvidia.com>
---
 drivers/mmc/host/sdhci-tegra.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
index 955c317..e82fb92 100644
--- a/drivers/mmc/host/sdhci-tegra.c
+++ b/drivers/mmc/host/sdhci-tegra.c
@@ -47,6 +47,9 @@
 #define SDHCI_MISC_CTRL_ENABLE_SDHCI_SPEC_300          0x20
 #define SDHCI_MISC_CTRL_ENABLE_DDR50                   0x200
 
+#define SDHCI_VNDR_TUN_CTRL0_0                         0x1c0
+#define SDHCI_VNDR_TUN_CTRL0_TUN_HW_TAP                        0x20000
+
 #define SDHCI_TEGRA_AUTO_CAL_CONFIG                    0x1e4
 #define SDHCI_AUTO_CAL_START                           BIT(31)
 #define SDHCI_AUTO_CAL_ENABLE                          BIT(29)
@@ -68,6 +71,7 @@
 #define NVQUIRK_ENABLE_DDR50                           BIT(5)
 #define NVQUIRK_HAS_PADCALIB                           BIT(6)
 #define NVQUIRK_NEEDS_PAD_CONTROL                      BIT(7)
+#define NVQUIRK_DIS_CARD_CLK_CONFIG_TAP                        BIT(8)
 
 struct sdhci_tegra_soc_data {
        const struct sdhci_pltfm_data *pdata;
@@ -500,12 +504,32 @@ static unsigned int tegra_sdhci_get_max_clock(struct 
sdhci_host *host)
 
 static void tegra_sdhci_set_tap(struct sdhci_host *host, unsigned int tap)
 {
+       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+       struct sdhci_tegra *tegra_host = sdhci_pltfm_priv(pltfm_host);
+       const struct sdhci_tegra_soc_data *soc_data = tegra_host->soc_data;
+       bool card_clk_enabled = false;
        u32 reg;
 
+       /*
+        * Touching the tap values is a bit tricky on some SoC generations.
+        * The quirk enables a workaround for a glitch that sometimes occurs if
+        * the tap values are changed.
+        */
+
+       if (soc_data->nvquirks & NVQUIRK_DIS_CARD_CLK_CONFIG_TAP)
+               card_clk_enabled = tegra_sdhci_configure_card_clk(host, false);
+
        reg = sdhci_readl(host, SDHCI_TEGRA_VENDOR_CLOCK_CTRL);
        reg &= ~SDHCI_CLOCK_CTRL_TAP_MASK;
        reg |= tap << SDHCI_CLOCK_CTRL_TAP_SHIFT;
        sdhci_writel(host, reg, SDHCI_TEGRA_VENDOR_CLOCK_CTRL);
+
+       if (soc_data->nvquirks & NVQUIRK_DIS_CARD_CLK_CONFIG_TAP &&
+           card_clk_enabled) {
+               usleep_range(1, 2);
+               sdhci_reset(host, SDHCI_RESET_CMD | SDHCI_RESET_DATA);
+               tegra_sdhci_configure_card_clk(host, card_clk_enabled);
+       }
 }
 
 static int tegra_sdhci_execute_tuning(struct sdhci_host *host, u32 opcode)
@@ -759,7 +783,8 @@ static const struct sdhci_pltfm_data sdhci_tegra210_pdata = 
{
 static const struct sdhci_tegra_soc_data soc_data_tegra210 = {
        .pdata = &sdhci_tegra210_pdata,
        .nvquirks = NVQUIRK_NEEDS_PAD_CONTROL |
-                   NVQUIRK_HAS_PADCALIB,
+                   NVQUIRK_HAS_PADCALIB |
+                   NVQUIRK_DIS_CARD_CLK_CONFIG_TAP,
 };
 
 static const struct sdhci_pltfm_data sdhci_tegra186_pdata = {
@@ -784,7 +809,8 @@ static const struct sdhci_pltfm_data sdhci_tegra186_pdata = 
{
 static const struct sdhci_tegra_soc_data soc_data_tegra186 = {
        .pdata = &sdhci_tegra186_pdata,
        .nvquirks = NVQUIRK_NEEDS_PAD_CONTROL |
-                   NVQUIRK_HAS_PADCALIB,
+                   NVQUIRK_HAS_PADCALIB |
+                   NVQUIRK_DIS_CARD_CLK_CONFIG_TAP,
 };
 
 static const struct of_device_id sdhci_tegra_dt_match[] = {
-- 
2.7.4