mmc: sdhci-msm: Disable CDR function on TX

commit a89e7bcb upstream.

The Clock Data Recovery (CDR) circuit allows to automatically adjust
the RX sampling-point/phase for high frequency cards (SDR104, HS200...).
CDR is automatically enabled during DLL configuration.
However, according to the APQ8016 reference manual, this function
must be disabled during TX and tuning phase in order to prevent any
interferences during tuning challenges and unexpected phase alteration
during TX transfers.

This patch enables/disables CDR according to the current transfer mode.

This fixes sporadic write transfer issues observed with some SDR104 and
HS200 cards.

Inspired by sdhci-msm downstream patch:
https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/432516/Reported-by: Leonid Segal <leonid.s@variscite.com>
Reported-by: Manabu Igusa <migusa@arrowjapan.com>
Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Georgi Djakov <georgi.djakov@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
[georgi: backport to v4.14]
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/mmc/host/sdhci-msm.c

@@ -138,6 +138,8 @@ struct sdhci_msm_host {
 	bool calibration_done;
 	u8 saved_tuning_phase;
 	bool use_cdclp533;
+	bool use_cdr;
+	u32 transfer_mode;
 };
 
 static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
@@ -815,6 +817,23 @@ static int sdhci_msm_hs400_dll_calibration(struct sdhci_host *host)
 	return ret;
 }
 
+static void sdhci_msm_set_cdr(struct sdhci_host *host, bool enable)
+{
+	u32 config, oldconfig = readl_relaxed(host->ioaddr + CORE_DLL_CONFIG);
+
+	config = oldconfig;
+	if (enable) {
+		config |= CORE_CDR_EN;
+		config &= ~CORE_CDR_EXT_EN;
+	} else {
+		config &= ~CORE_CDR_EN;
+		config |= CORE_CDR_EXT_EN;
+	}
+
+	if (config != oldconfig)
+		writel_relaxed(config, host->ioaddr + CORE_DLL_CONFIG);
+}
+
 static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
 {
 	struct sdhci_host *host = mmc_priv(mmc);
@@ -832,8 +851,14 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
 	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.timing == MMC_TIMING_UHS_SDR104)) {
+		msm_host->use_cdr = false;
+		sdhci_msm_set_cdr(host, false);
 		return 0;
+	}
+
+	/* Clock-Data-Recovery used to dynamically adjust RX sampling point */
+	msm_host->use_cdr = true;
 
 	/*
 	 * For HS400 tuning in HS200 timing requires:
@@ -1092,6 +1117,29 @@ static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
 	__sdhci_msm_set_clock(host, clock);
 }
 
+static void sdhci_msm_write_w(struct sdhci_host *host, u16 val, int reg)
+{
+	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
+
+	switch (reg) {
+	case SDHCI_TRANSFER_MODE:
+		msm_host->transfer_mode = val;
+		break;
+	case SDHCI_COMMAND:
+		if (!msm_host->use_cdr)
+			break;
+		if ((msm_host->transfer_mode & SDHCI_TRNS_READ) &&
+		    (SDHCI_GET_CMD(val) != MMC_SEND_TUNING_BLOCK_HS200) &&
+		    (SDHCI_GET_CMD(val) != MMC_SEND_TUNING_BLOCK))
+			sdhci_msm_set_cdr(host, true);
+		else
+			sdhci_msm_set_cdr(host, false);
+		break;
+	}
+	writew(val, host->ioaddr + reg);
+}
+
 static const struct of_device_id sdhci_msm_dt_match[] = {
 	{ .compatible = "qcom,sdhci-msm-v4" },
 	{},
@@ -1107,6 +1155,7 @@ static const struct sdhci_ops sdhci_msm_ops = {
 	.set_bus_width = sdhci_set_bus_width,
 	.set_uhs_signaling = sdhci_msm_set_uhs_signaling,
 	.voltage_switch = sdhci_msm_voltage_switch,
+	.write_w = sdhci_msm_write_w,
 };
 
 static const struct sdhci_pltfm_data sdhci_msm_pdata = {