mmc: core: add support for eMMC Dual Data Rate

eMMC voltage change not required for 1.8V.  3.3V and 1.8V vcc
are capable of doing DDR. vccq of 1.8v is not required.
Signed-off-by: Philip Rakity <prakity@marvell.com>
Reviewed-by: Arindam Nath <arindam.nath@amd.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/core/core.c

@@ -717,23 +717,13 @@ void mmc_set_bus_mode(struct mmc_host *host, unsigned int mode)
 	mmc_set_ios(host);
 }
 
-/*
- * Change data bus width and DDR mode of a host.
- */
-void mmc_set_bus_width_ddr(struct mmc_host *host, unsigned int width,
-			   unsigned int ddr)
-{
-	host->ios.bus_width = width;
-	host->ios.ddr = ddr;
-	mmc_set_ios(host);
-}
-
 /*
  * Change data bus width of a host.
  */
 void mmc_set_bus_width(struct mmc_host *host, unsigned int width)
 {
-	mmc_set_bus_width_ddr(host, width, MMC_SDR_MODE);
+	host->ios.bus_width = width;
+	mmc_set_ios(host);
 }
 
 /**

drivers/mmc/core/core.h

@@ -38,8 +38,6 @@ void mmc_ungate_clock(struct mmc_host *host);
 void mmc_set_ungated(struct mmc_host *host);
 void mmc_set_bus_mode(struct mmc_host *host, unsigned int mode);
 void mmc_set_bus_width(struct mmc_host *host, unsigned int width);
-void mmc_set_bus_width_ddr(struct mmc_host *host, unsigned int width,
-			   unsigned int ddr);
 u32 mmc_select_voltage(struct mmc_host *host, u32 ocr);
 int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage,
 			   bool cmd11);

drivers/mmc/core/mmc.c

@@ -20,6 +20,7 @@
 #include "core.h"
 #include "bus.h"
 #include "mmc_ops.h"
+#include "sd_ops.h"
 
 static const unsigned int tran_exp[] = {
 	10000,		100000,		1000000,	10000000,
@@ -633,10 +634,14 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 	 */
 	if (mmc_card_highspeed(card)) {
 		if ((card->ext_csd.card_type & EXT_CSD_CARD_TYPE_DDR_1_8V)
-			&& (host->caps & (MMC_CAP_1_8V_DDR)))
+			&& ((host->caps & (MMC_CAP_1_8V_DDR |
+			     MMC_CAP_UHS_DDR50))
+				== (MMC_CAP_1_8V_DDR | MMC_CAP_UHS_DDR50)))
 				ddr = MMC_1_8V_DDR_MODE;
 		else if ((card->ext_csd.card_type & EXT_CSD_CARD_TYPE_DDR_1_2V)
-			&& (host->caps & (MMC_CAP_1_2V_DDR)))
+			&& ((host->caps & (MMC_CAP_1_2V_DDR |
+			     MMC_CAP_UHS_DDR50))
+				== (MMC_CAP_1_2V_DDR | MMC_CAP_UHS_DDR50)))
 				ddr = MMC_1_2V_DDR_MODE;
 	}
 
@@ -670,8 +675,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 					 ext_csd_bits[idx][0],
 					 0);
 			if (!err) {
-				mmc_set_bus_width_ddr(card->host,
-						      bus_width, MMC_SDR_MODE);
+				mmc_set_bus_width(card->host, bus_width);
 				/*
 				 * If controller can't handle bus width test,
 				 * use the highest bus width to maintain
@@ -697,8 +701,29 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 				1 << bus_width, ddr);
 			goto free_card;
 		} else if (ddr) {
+			/*
+			 * eMMC cards can support 3.3V to 1.2V i/o (vccq)
+			 * signaling.
+			 *
+			 * EXT_CSD_CARD_TYPE_DDR_1_8V means 3.3V or 1.8V vccq.
+			 *
+			 * 1.8V vccq at 3.3V core voltage (vcc) is not required
+			 * in the JEDEC spec for DDR.
+			 *
+			 * Do not force change in vccq since we are obviously
+			 * working and no change to vccq is needed.
+			 *
+			 * WARNING: eMMC rules are NOT the same as SD DDR
+			 */
+			if (ddr == EXT_CSD_CARD_TYPE_DDR_1_2V) {
+				err = mmc_set_signal_voltage(host,
+					MMC_SIGNAL_VOLTAGE_120, 0);
+				if (err)
+					goto err;
+			}
 			mmc_card_set_ddr_mode(card);
-			mmc_set_bus_width_ddr(card->host, bus_width, ddr);
+			mmc_set_timing(card->host, MMC_TIMING_UHS_DDR50);
+			mmc_set_bus_width(card->host, bus_width);
 		}
 	}
 

include/linux/mmc/host.h

@@ -66,6 +66,7 @@ struct mmc_ios {
 
 #define MMC_SIGNAL_VOLTAGE_330	0
 #define MMC_SIGNAL_VOLTAGE_180	1
+#define MMC_SIGNAL_VOLTAGE_120	2
 
 	unsigned char	drv_type;		/* driver type (A, B, C, D) */