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Subject[PATCH v2 20/40] mmc: tegra: Add a workaround for tap value change glitch
Date
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 <avienamo@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
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