[PATCH v3 09/11] mmc: sdhci: enable preset value after uhs initialization

[Arindam Nath <arindam.nath@amd.com>]

According to the Host Controller spec v3.00, setting Preset Value Enable
in the Host Control2 register lets SDCLK Frequency Select, Clock Generator
Select and Driver Strength Select to be set automatically by the Host
Controller based on the UHS-I mode set. This patch enables this feature.
We also reset Preset Value Enable next time before initialization.

Signed-off-by: Arindam Nath <arindam.nath@amd.com>
---
 drivers/mmc/core/sd.c    |   11 +++++++++++
 drivers/mmc/host/sdhci.c |   32 ++++++++++++++++++++++++++++++++
 include/linux/mmc/host.h |    1 +
 3 files changed, 44 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index f3ecdef..08305ab 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -959,6 +959,13 @@ static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
 		}
 	}
 
+	/*
+	 * Since initialization is now complete, enable preset
+	 * value registers.
+	 */
+	if (host->ops->enable_preset_value)
+		host->ops->enable_preset_value(host, 1);
+
 	host->card = card;
 	return 0;
 
@@ -1109,6 +1116,10 @@ int mmc_attach_sd(struct mmc_host *host)
 	if (err)
 		return err;
 
+	/* Disable preset value enable if already set from last time */
+	if (host->ops->enable_preset_value)
+		host->ops->enable_preset_value(host, 0);
+
 	/*
 	 * We need to get OCR a different way for SPI.
 	 */
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 9065157..c25ab83 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1614,6 +1614,37 @@ out:
 	return err;
 }
 
+static void sdhci_enable_preset_value(struct mmc_host *mmc, int enable)
+{
+	struct sdhci_host *host;
+	u16 ctrl;
+	unsigned long flags;
+
+	host = mmc_priv(mmc);
+
+	/* Host Controller v3.00 defines preset value registers */
+	if (host->version < SDHCI_SPEC_300)
+		return;
+
+	spin_lock_irqsave(&host->lock, flags);
+
+	ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
+
+	/*
+	 * We only enable or disable Preset Value if they are not already
+	 * enabled or disabled respectively. Otherwise, we bail out.
+	 */
+	if (enable && !(ctrl & SDHCI_CTRL_PRESET_VAL_ENABLE)) {
+		ctrl |= SDHCI_CTRL_PRESET_VAL_ENABLE;
+		sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
+	} else if (!enable && (ctrl & SDHCI_CTRL_PRESET_VAL_ENABLE)) {
+		ctrl &= ~SDHCI_CTRL_PRESET_VAL_ENABLE;
+		sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
+	}
+
+	spin_unlock_irqrestore(&host->lock, flags);
+}
+
 static const struct mmc_host_ops sdhci_ops = {
 	.request	= sdhci_request,
 	.set_ios	= sdhci_set_ios,
@@ -1621,6 +1652,7 @@ static const struct mmc_host_ops sdhci_ops = {
 	.enable_sdio_irq = sdhci_enable_sdio_irq,
 	.start_signal_voltage_switch	= sdhci_start_signal_voltage_switch,
 	.execute_tuning			= sdhci_execute_tuning,
+	.enable_preset_value		= sdhci_enable_preset_value,
 };
 
 /*****************************************************************************\
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index ca7007f..2209e01 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -137,6 +137,7 @@ struct mmc_host_ops {
 
 	int	(*start_signal_voltage_switch)(struct mmc_host *host, struct mmc_ios *ios);
 	int	(*execute_tuning)(struct mmc_host *host);
+	void	(*enable_preset_value)(struct mmc_host *host, int enable);
 };
 
 struct mmc_card;
-- 
1.7.1