[PATCH V2 1/4] mmc: sdhci: Fix voltage switch delay

[Adrian Hunter <adrian.hunter@intel.com>]

Commit 20b92a30b561 ("mmc: sdhci: update signal voltage switch code")
removed voltage switch delays from sdhci because mmc core had been
enhanced to support them. However that assumed that sdhci_set_ios()
did a single clock change, which it did not, and so the delays in mmc
core, which should have come after the first clock change, were not
effective.

Fix by avoiding re-configuring UHS and preset settings when the clock
is turning on and the settings have not changed. That then also avoids
the associated clock changes, so that then sdhci_set_ios() does a single
clock change when voltage switching, and the mmc core delays become
effective.

To do that has meant keeping track of driver strength (host->drv_type),
and cases of reinitialization (host->reinit_uhs).

Note also, the 'turning_on_clk' restriction should not be necessary
but is done to minimize the impact of the change on stable kernels.

Fixes: 20b92a30b561 ("mmc: sdhci: update signal voltage switch code")
Cc: stable@vger.kernel.org
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 drivers/mmc/host/sdhci.c | 61 +++++++++++++++++++++++++++++++++++-----
 drivers/mmc/host/sdhci.h |  2 ++
 2 files changed, 56 insertions(+), 7 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 2108e8075609..64750fbb0ac8 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -373,6 +373,7 @@ static void sdhci_init(struct sdhci_host *host, int soft)
 	if (soft) {
 		/* force clock reconfiguration */
 		host->clock = 0;
+		host->reinit_uhs = true;
 		mmc->ops->set_ios(mmc, &mmc->ios);
 	}
 }
@@ -2279,11 +2280,46 @@ void sdhci_set_uhs_signaling(struct sdhci_host *host, unsigned timing)
 }
 EXPORT_SYMBOL_GPL(sdhci_set_uhs_signaling);
 
+static bool sdhci_timing_has_preset(unsigned char timing)
+{
+	switch (timing) {
+	case MMC_TIMING_UHS_SDR12:
+	case MMC_TIMING_UHS_SDR25:
+	case MMC_TIMING_UHS_SDR50:
+	case MMC_TIMING_UHS_SDR104:
+	case MMC_TIMING_UHS_DDR50:
+	case MMC_TIMING_MMC_DDR52:
+		return true;
+	};
+	return false;
+}
+
+static bool sdhci_preset_needed(struct sdhci_host *host, unsigned char timing)
+{
+	return !(host->quirks2 & SDHCI_QUIRK2_PRESET_VALUE_BROKEN) &&
+	       sdhci_timing_has_preset(timing);
+}
+
+static bool sdhci_presetable_values_change(struct sdhci_host *host, struct mmc_ios *ios)
+{
+	/*
+	 * Preset Values are: Driver Strength, Clock Generator and SDCLK/RCLK
+	 * Frequency. Check if preset values need to be enabled, or the Driver
+	 * Strength needs updating. Note, clock changes are handled separately.
+	 */
+	return !host->preset_enabled &&
+	       (sdhci_preset_needed(host, ios->timing) || host->drv_type != ios->drv_type);
+}
+
 void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 {
 	struct sdhci_host *host = mmc_priv(mmc);
+	bool reinit_uhs = host->reinit_uhs;
+	bool turning_on_clk = false;
 	u8 ctrl;
 
+	host->reinit_uhs = false;
+
 	if (ios->power_mode == MMC_POWER_UNDEFINED)
 		return;
 
@@ -2309,6 +2345,8 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 		sdhci_enable_preset_value(host, false);
 
 	if (!ios->clock || ios->clock != host->clock) {
+		turning_on_clk = ios->clock && !host->clock;
+
 		host->ops->set_clock(host, ios->clock);
 		host->clock = ios->clock;
 
@@ -2335,6 +2373,17 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 
 	host->ops->set_bus_width(host, ios->bus_width);
 
+	/*
+	 * Special case to avoid multiple clock changes during voltage
+	 * switching.
+	 */
+	if (!reinit_uhs &&
+	    turning_on_clk &&
+	    host->timing == ios->timing &&
+	    host->version >= SDHCI_SPEC_300 &&
+	    !sdhci_presetable_values_change(host, ios))
+		return;
+
 	ctrl = sdhci_readb(host, SDHCI_HOST_CONTROL);
 
 	if (!(host->quirks & SDHCI_QUIRK_NO_HISPD_BIT)) {
@@ -2378,6 +2427,7 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 			}
 
 			sdhci_writew(host, ctrl_2, SDHCI_HOST_CONTROL2);
+			host->drv_type = ios->drv_type;
 		} else {
 			/*
 			 * According to SDHC Spec v3.00, if the Preset Value
@@ -2405,19 +2455,14 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 		host->ops->set_uhs_signaling(host, ios->timing);
 		host->timing = ios->timing;
 
-		if (!(host->quirks2 & SDHCI_QUIRK2_PRESET_VALUE_BROKEN) &&
-				((ios->timing == MMC_TIMING_UHS_SDR12) ||
-				 (ios->timing == MMC_TIMING_UHS_SDR25) ||
-				 (ios->timing == MMC_TIMING_UHS_SDR50) ||
-				 (ios->timing == MMC_TIMING_UHS_SDR104) ||
-				 (ios->timing == MMC_TIMING_UHS_DDR50) ||
-				 (ios->timing == MMC_TIMING_MMC_DDR52))) {
+		if (sdhci_preset_needed(host, ios->timing)) {
 			u16 preset;
 
 			sdhci_enable_preset_value(host, true);
 			preset = sdhci_get_preset_value(host);
 			ios->drv_type = FIELD_GET(SDHCI_PRESET_DRV_MASK,
 						  preset);
+			host->drv_type = ios->drv_type;
 		}
 
 		/* Re-enable SD Clock */
@@ -3754,6 +3799,7 @@ int sdhci_resume_host(struct sdhci_host *host)
 		sdhci_init(host, 0);
 		host->pwr = 0;
 		host->clock = 0;
+		host->reinit_uhs = true;
 		mmc->ops->set_ios(mmc, &mmc->ios);
 	} else {
 		sdhci_init(host, (mmc->pm_flags & MMC_PM_KEEP_POWER));
@@ -3816,6 +3862,7 @@ int sdhci_runtime_resume_host(struct sdhci_host *host, int soft_reset)
 		/* Force clock and power re-program */
 		host->pwr = 0;
 		host->clock = 0;
+		host->reinit_uhs = true;
 		mmc->ops->start_signal_voltage_switch(mmc, &mmc->ios);
 		mmc->ops->set_ios(mmc, &mmc->ios);
 
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 908da47ac5ba..b6f31a7d6152 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -524,6 +524,8 @@ struct sdhci_host {
 
 	unsigned int clock;	/* Current clock (MHz) */
 	u8 pwr;			/* Current voltage */
+	u8 drv_type;		/* Current UHS-I driver type */
+	bool reinit_uhs;	/* Force UHS-related re-initialization */
 
 	bool runtime_suspended;	/* Host is runtime suspended */
 	bool bus_on;		/* Bus power prevents runtime suspend */
-- 
2.34.1