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Subject[PATCH V5 2/2] mmc: sdhci-msm: Re-initialize DLL if MCLK is gated dynamically
Date
On few SDHCI-MSM controllers, the host controller's clock tuning
circuit may go out of sync if controller clocks are gated which
eventually will result in data CRC, command CRC/timeout errors.
To overcome this h/w limitation, the DLL needs to be re-initialized
and restored with its old settings once clocks are ungated.

Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
---
drivers/mmc/host/sdhci-msm.c | 78 +++++++++++++++++++++++++++++++++++++-------
1 file changed, 67 insertions(+), 11 deletions(-)

diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index 3cc8bfe..4cac593 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -232,6 +232,7 @@ struct sdhci_msm_variant_ops {
*/
struct sdhci_msm_variant_info {
bool mci_removed;
+ bool restore_dll_config;
const struct sdhci_msm_variant_ops *var_ops;
const struct sdhci_msm_offset *offset;
};
@@ -256,6 +257,7 @@ struct sdhci_msm_host {
bool pwr_irq_flag;
u32 caps_0;
bool mci_removed;
+ bool restore_dll_config;
const struct sdhci_msm_variant_ops *var_ops;
const struct sdhci_msm_offset *offset;
};
@@ -1025,6 +1027,48 @@ static int sdhci_msm_hs400_dll_calibration(struct sdhci_host *host)
return ret;
}

+static bool sdhci_msm_is_tuning_needed(struct sdhci_host *host)
+{
+ struct mmc_ios *ios = &host->mmc->ios;
+
+ /*
+ * Tuning is required for SDR104, HS200 and HS400 cards and
+ * if clock frequency is greater than 100MHz in these modes.
+ */
+ if (host->clock <= CORE_FREQ_100MHZ ||
+ !(ios->timing == MMC_TIMING_MMC_HS400 ||
+ ios->timing == MMC_TIMING_MMC_HS200 ||
+ ios->timing == MMC_TIMING_UHS_SDR104) ||
+ ios->enhanced_strobe)
+ return false;
+
+ return true;
+}
+
+static int sdhci_msm_restore_sdr_dll_config(struct sdhci_host *host)
+{
+ struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+ struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
+ int ret;
+
+ /*
+ * SDR DLL comes into picture only for timing modes which needs
+ * tuning.
+ */
+ if (!sdhci_msm_is_tuning_needed(host))
+ return 0;
+
+ /* Reset the tuning block */
+ ret = msm_init_cm_dll(host);
+ if (ret)
+ return ret;
+
+ /* Restore the tuning block */
+ ret = msm_config_cm_dll_phase(host, msm_host->saved_tuning_phase);
+
+ return ret;
+}
+
static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
{
struct sdhci_host *host = mmc_priv(mmc);
@@ -1035,14 +1079,7 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);

- /*
- * Tuning is required for SDR104, HS200 and HS400 cards and
- * if clock frequency is greater than 100MHz in these modes.
- */
- if (host->clock <= CORE_FREQ_100MHZ ||
- !(ios.timing == MMC_TIMING_MMC_HS400 ||
- ios.timing == MMC_TIMING_MMC_HS200 ||
- ios.timing == MMC_TIMING_UHS_SDR104))
+ if (!sdhci_msm_is_tuning_needed(host))
return 0;

/*
@@ -1069,7 +1106,6 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
if (rc)
return rc;

- msm_host->saved_tuning_phase = phase;
rc = mmc_send_tuning(mmc, opcode, NULL);
if (!rc) {
/* Tuning is successful at this tuning point */
@@ -1094,6 +1130,7 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
rc = msm_config_cm_dll_phase(host, phase);
if (rc)
return rc;
+ msm_host->saved_tuning_phase = phase;
dev_dbg(mmc_dev(mmc), "%s: Setting the tuning phase to %d\n",
mmc_hostname(mmc), phase);
} else {
@@ -1616,7 +1653,6 @@ static void sdhci_msm_set_regulator_caps(struct sdhci_msm_host *msm_host)
};

static const struct sdhci_msm_variant_info sdhci_msm_mci_var = {
- .mci_removed = false,
.var_ops = &mci_var_ops,
.offset = &sdhci_msm_mci_offset,
};
@@ -1627,9 +1663,17 @@ static void sdhci_msm_set_regulator_caps(struct sdhci_msm_host *msm_host)
.offset = &sdhci_msm_v5_offset,
};

+static const struct sdhci_msm_variant_info sdm845_sdhci_var = {
+ .mci_removed = true,
+ .restore_dll_config = true,
+ .var_ops = &v5_var_ops,
+ .offset = &sdhci_msm_v5_offset,
+};
+
static const struct of_device_id sdhci_msm_dt_match[] = {
{.compatible = "qcom,sdhci-msm-v4", .data = &sdhci_msm_mci_var},
{.compatible = "qcom,sdhci-msm-v5", .data = &sdhci_msm_v5_var},
+ {.compatible = "qcom,sdm845-sdhci", .data = &sdm845_sdhci_var},
{},
};

@@ -1689,6 +1733,7 @@ static int sdhci_msm_probe(struct platform_device *pdev)
var_info = of_device_get_match_data(&pdev->dev);

msm_host->mci_removed = var_info->mci_removed;
+ msm_host->restore_dll_config = var_info->restore_dll_config;
msm_host->var_ops = var_info->var_ops;
msm_host->offset = var_info->offset;

@@ -1928,9 +1973,20 @@ static int sdhci_msm_runtime_resume(struct device *dev)
struct sdhci_host *host = dev_get_drvdata(dev);
struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
+ int ret;

- return clk_bulk_prepare_enable(ARRAY_SIZE(msm_host->bulk_clks),
+ ret = clk_bulk_prepare_enable(ARRAY_SIZE(msm_host->bulk_clks),
msm_host->bulk_clks);
+ if (ret)
+ return ret;
+ /*
+ * Whenever core-clock is gated dynamically, it's needed to
+ * restore the SDR DLL settings when the clock is ungated.
+ */
+ if (msm_host->restore_dll_config && msm_host->clk_rate)
+ return sdhci_msm_restore_sdr_dll_config(host);
+
+ return 0;
}
#endif

--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
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