mmc: mmc: Read card's valid driver strength mask

In preparation for supporing drive strength selection
for eMMC, read the card's valid driver strengths.

Note that though the SD spec uses the term "drive strength",
the JEDEC eMMC spec uses the term "driver strength".
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/mmc.c

@@ -437,6 +437,7 @@ static int mmc_decode_ext_csd(struct mmc_card *card, u8 *ext_csd)
 	card->ext_csd.raw_trim_mult =
 		ext_csd[EXT_CSD_TRIM_MULT];
 	card->ext_csd.raw_partition_support = ext_csd[EXT_CSD_PARTITION_SUPPORT];
+	card->ext_csd.raw_driver_strength = ext_csd[EXT_CSD_DRIVER_STRENGTH];
 	if (card->ext_csd.rev >= 4) {
 		if (ext_csd[EXT_CSD_PARTITION_SETTING_COMPLETED] &
 		    EXT_CSD_PART_SETTING_COMPLETED)

include/linux/mmc/card.h

@@ -97,6 +97,7 @@ struct mmc_ext_csd {
 	u8			raw_erased_mem_count;	/* 181 */
 	u8			raw_ext_csd_structure;	/* 194 */
 	u8			raw_card_type;		/* 196 */
+	u8			raw_driver_strength;	/* 197 */
 	u8			out_of_int_time;	/* 198 */
 	u8			raw_pwr_cl_52_195;	/* 200 */
 	u8			raw_pwr_cl_26_195;	/* 201 */

include/linux/mmc/mmc.h

@@ -302,6 +302,7 @@ struct _mmc_csd {
 #define EXT_CSD_REV			192	/* RO */
 #define EXT_CSD_STRUCTURE		194	/* RO */
 #define EXT_CSD_CARD_TYPE		196	/* RO */
+#define EXT_CSD_DRIVER_STRENGTH		197	/* RO */
 #define EXT_CSD_OUT_OF_INTERRUPT_TIME	198	/* RO */
 #define EXT_CSD_PART_SWITCH_TIME        199     /* RO */
 #define EXT_CSD_PWR_CL_52_195		200	/* RO */