mmc: core: eMMC 4.5 Power Class Selection Feature

This patch adds the power class selection feature available for mmc
versions 4.0 and above.  During the enumeration stage before switching
to the lower data bus, check if the power class is supported for the
current bus width. If the power class is available then switch to the
power class and use the higher data bus. If power class is not supported
then switch to the lower data bus in a worst case.

Signed-off-by: Girish K S <girish.shivananjappa@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 96 insertions, 0 deletions

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 7adc30da8366..c2334d636fe8 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -532,6 +532,86 @@ static struct device_type mmc_type = {
 };
 
 /*
+ * Select the PowerClass for the current bus width
+ * If power class is defined for 4/8 bit bus in the
+ * extended CSD register, select it by executing the
+ * mmc_switch command.
+ */
+static int mmc_select_powerclass(struct mmc_card *card,
+		unsigned int bus_width, u8 *ext_csd)
+{
+	int err = 0;
+	unsigned int pwrclass_val;
+	unsigned int index = 0;
+	struct mmc_host *host;
+
+	BUG_ON(!card);
+
+	host = card->host;
+	BUG_ON(!host);
+
+	if (ext_csd == NULL)
+		return 0;
+
+	/* Power class selection is supported for versions >= 4.0 */
+	if (card->csd.mmca_vsn < CSD_SPEC_VER_4)
+		return 0;
+
+	/* Power class values are defined only for 4/8 bit bus */
+	if (bus_width == EXT_CSD_BUS_WIDTH_1)
+		return 0;
+
+	switch (1 << host->ios.vdd) {
+	case MMC_VDD_165_195:
+		if (host->ios.clock <= 26000000)
+			index = EXT_CSD_PWR_CL_26_195;
+		else if	(host->ios.clock <= 52000000)
+			index = (bus_width <= EXT_CSD_BUS_WIDTH_8) ?
+				EXT_CSD_PWR_CL_52_195 :
+				EXT_CSD_PWR_CL_DDR_52_195;
+		else if (host->ios.clock <= 200000000)
+			index = EXT_CSD_PWR_CL_200_195;
+		break;
+	case MMC_VDD_32_33:
+	case MMC_VDD_33_34:
+	case MMC_VDD_34_35:
+	case MMC_VDD_35_36:
+		if (host->ios.clock <= 26000000)
+			index = EXT_CSD_PWR_CL_26_360;
+		else if	(host->ios.clock <= 52000000)
+			index = (bus_width <= EXT_CSD_BUS_WIDTH_8) ?
+				EXT_CSD_PWR_CL_52_360 :
+				EXT_CSD_PWR_CL_DDR_52_360;
+		else if (host->ios.clock <= 200000000)
+			index = EXT_CSD_PWR_CL_200_360;
+		break;
+	default:
+		pr_warning("%s: Voltage range not supported "
+			   "for power class.\n", mmc_hostname(host));
+		return -EINVAL;
+	}
+
+	pwrclass_val = ext_csd[index];
+
+	if (bus_width & (EXT_CSD_BUS_WIDTH_8 | EXT_CSD_DDR_BUS_WIDTH_8))
+		pwrclass_val = (pwrclass_val & EXT_CSD_PWR_CL_8BIT_MASK) >>
+				EXT_CSD_PWR_CL_8BIT_SHIFT;
+	else
+		pwrclass_val = (pwrclass_val & EXT_CSD_PWR_CL_4BIT_MASK) >>
+				EXT_CSD_PWR_CL_4BIT_SHIFT;
+
+	/* If the power class is different from the default value */
+	if (pwrclass_val > 0) {
+		err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
+				 EXT_CSD_POWER_CLASS,
+				 pwrclass_val,
+				 0);
+	}
+
+	return err;
+}
+
+/*
  * Handle the detection and initialisation of a card.
  *
  * In the case of a resume, "oldcard" will contain the card
@@ -787,6 +867,14 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 			bus_width = bus_widths[idx];
 			if (bus_width == MMC_BUS_WIDTH_1)
 				ddr = 0; /* no DDR for 1-bit width */
+			err = mmc_select_powerclass(card, ext_csd_bits[idx][0],
+						    ext_csd);
+			if (err)
+				pr_err("%s: power class selection to "
+				       "bus width %d failed\n",
+				       mmc_hostname(card->host),
+				       1 << bus_width);
+
 			err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
 					 EXT_CSD_BUS_WIDTH,
 					 ext_csd_bits[idx][0],
@@ -810,6 +898,14 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 		}
 
 		if (!err && ddr) {
+			err = mmc_select_powerclass(card, ext_csd_bits[idx][1],
+						    ext_csd);
+			if (err)
+				pr_err("%s: power class selection to "
+				       "bus width %d ddr %d failed\n",
+				       mmc_hostname(card->host),
+				       1 << bus_width, ddr);
+
 			err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
 					 EXT_CSD_BUS_WIDTH,
 					 ext_csd_bits[idx][1],