[PATCH 2/2] mmc: sdhci-msm: Re-initialize DLL if MCLK is gated dynamically

[Veerabhadrarao Badiganti <vbadigan@codeaurora.org>]

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 | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index 486462d..4a83850 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -18,6 +18,7 @@
 #include <linux/of_device.h>
 #include <linux/delay.h>
 #include <linux/mmc/mmc.h>
+#include <linux/mmc/host.h>
 #include <linux/pm_runtime.h>
 #include <linux/slab.h>
 #include <linux/iopoll.h>
@@ -264,6 +265,8 @@ struct sdhci_msm_host {
 	u32 vmmc_level[2];
 	bool vqmmc_load;
 	u32 vqmmc_level[2];
+	bool restore_dll_cfg_needed;
+	bool restore_dll_cfg;
 };
 
 static const struct sdhci_msm_offset *sdhci_priv_msm_offset(struct sdhci_host *host)
@@ -1068,6 +1071,20 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
 	if (rc)
 		return rc;
 
+	/*
+	 * If restore dll config flag is set, then just program the DLL with
+	 * last saved tuning phase. If this operation fails, proceed with
+	 * full-fledged tuning.
+	 */
+	if (msm_host->restore_dll_cfg) {
+		rc = msm_config_cm_dll_phase(host,
+				msm_host->saved_tuning_phase);
+		msm_host->restore_dll_cfg = false;
+		if (!rc)
+			return rc;
+
+	}
+
 	phase = 0;
 	do {
 		/* Set the phase in delay line hw block */
@@ -1075,7 +1092,6 @@ 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 */
@@ -1100,6 +1116,7 @@ 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 {
@@ -2049,6 +2066,9 @@ static int sdhci_msm_probe(struct platform_device *pdev)
 		goto clk_disable;
 	}
 
+	if (device_property_read_bool(&pdev->dev, "qcom,restore-dll-config"))
+		msm_host->restore_dll_cfg_needed = true;
+
 	pm_runtime_get_noresume(&pdev->dev);
 	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);
@@ -2124,6 +2144,15 @@ static int sdhci_msm_runtime_resume(struct device *dev)
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
 	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
 
+	/*
+	 * Whenever core-clock is gated dynamically, it's needed to
+	 * re-initialize the DLL when the clock is ungated.
+	 */
+	if (msm_host->restore_dll_cfg_needed && msm_host->clk_rate) {
+		msm_host->restore_dll_cfg = true;
+		mmc_retune_needed(host->mmc);
+	}
+
 	return clk_bulk_prepare_enable(ARRAY_SIZE(msm_host->bulk_clks),
 				       msm_host->bulk_clks);
 }
-- 
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