mmc: core: Allow card drive strength to be different to host

Initialization of UHS-I modes for SD and SDIO cards
employs a callback to allow the host driver to
choose a drive strength value. Currently that
assumes the card drive strength and host driver
type must be the same value. Change to let the
callback make that decision and return both the
card drive strength and host driver type.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/sd.c

@@ -388,18 +388,9 @@ static int sd_select_driver_type(struct mmc_card *card, u8 *status)
 {
 	int host_drv_type = SD_DRIVER_TYPE_B;
 	int card_drv_type = SD_DRIVER_TYPE_B;
-	int drive_strength;
+	int drive_strength, drv_type;
 	int err;
 
-	/*
-	 * If the host doesn't support any of the Driver Types A,C or D,
-	 * or there is no board specific handler then default Driver
-	 * Type B is used.
-	 */
-	if (!(card->host->caps & (MMC_CAP_DRIVER_TYPE_A | MMC_CAP_DRIVER_TYPE_C
-	    | MMC_CAP_DRIVER_TYPE_D)))
-		return 0;
-
 	if (!card->host->ops->select_drive_strength)
 		return 0;
 
@@ -430,20 +421,22 @@ static int sd_select_driver_type(struct mmc_card *card, u8 *status)
 	mmc_host_clk_hold(card->host);
 	drive_strength = card->host->ops->select_drive_strength(
 		card->sw_caps.uhs_max_dtr,
-		host_drv_type, card_drv_type);
+		host_drv_type, card_drv_type, &drv_type);
 	mmc_host_clk_release(card->host);
 
-	err = mmc_sd_switch(card, 1, 2, drive_strength, status);
-	if (err)
-		return err;
-
-	if ((status[15] & 0xF) != drive_strength) {
-		pr_warn("%s: Problem setting drive strength!\n",
-			mmc_hostname(card->host));
-		return 0;
+	if (drive_strength) {
+		err = mmc_sd_switch(card, 1, 2, drive_strength, status);
+		if (err)
+			return err;
+		if ((status[15] & 0xF) != drive_strength) {
+			pr_warn("%s: Problem setting drive strength!\n",
+				mmc_hostname(card->host));
+			return 0;
+		}
 	}
 
-	mmc_set_driver_type(card->host, drive_strength);
+	if (drv_type)
+		mmc_set_driver_type(card->host, drv_type);
 
 	return 0;
 }

drivers/mmc/core/sdio.c

@@ -404,21 +404,10 @@ static void sdio_select_driver_type(struct mmc_card *card)
 {
 	int host_drv_type = SD_DRIVER_TYPE_B;
 	int card_drv_type = SD_DRIVER_TYPE_B;
-	int drive_strength;
+	int drive_strength, drv_type;
 	unsigned char card_strength;
 	int err;
 
-	/*
-	 * If the host doesn't support any of the Driver Types A,C or D,
-	 * or there is no board specific handler then default Driver
-	 * Type B is used.
-	 */
-	if (!(card->host->caps &
-		(MMC_CAP_DRIVER_TYPE_A |
-		 MMC_CAP_DRIVER_TYPE_C |
-		 MMC_CAP_DRIVER_TYPE_D)))
-		return;
-
 	if (!card->host->ops->select_drive_strength)
 		return;
 
@@ -448,23 +437,27 @@ static void sdio_select_driver_type(struct mmc_card *card)
 	 */
 	drive_strength = card->host->ops->select_drive_strength(
 		card->sw_caps.uhs_max_dtr,
-		host_drv_type, card_drv_type);
+		host_drv_type, card_drv_type, &drv_type);
 
-	/* if error just use default for drive strength B */
-	err = mmc_io_rw_direct(card, 0, 0, SDIO_CCCR_DRIVE_STRENGTH, 0,
-		&card_strength);
-	if (err)
-		return;
+	if (drive_strength) {
+		/* if error just use default for drive strength B */
+		err = mmc_io_rw_direct(card, 0, 0, SDIO_CCCR_DRIVE_STRENGTH, 0,
+				       &card_strength);
+		if (err)
+			return;
 
-	card_strength &= ~(SDIO_DRIVE_DTSx_MASK<<SDIO_DRIVE_DTSx_SHIFT);
-	card_strength |= host_drive_to_sdio_drive(drive_strength);
+		card_strength &= ~(SDIO_DRIVE_DTSx_MASK<<SDIO_DRIVE_DTSx_SHIFT);
+		card_strength |= host_drive_to_sdio_drive(drive_strength);
 
-	err = mmc_io_rw_direct(card, 1, 0, SDIO_CCCR_DRIVE_STRENGTH,
-		card_strength, NULL);
+		/* if error default to drive strength B */
+		err = mmc_io_rw_direct(card, 1, 0, SDIO_CCCR_DRIVE_STRENGTH,
+				       card_strength, NULL);
+		if (err)
+			return;
+	}
 
-	/* if error default to drive strength B */
-	if (!err)
-		mmc_set_driver_type(card->host, drive_strength);
+	if (drv_type)
+		mmc_set_driver_type(card->host, drv_type);
 }
 
 

include/linux/mmc/host.h

@@ -132,7 +132,8 @@ struct mmc_host_ops {
 
 	/* Prepare HS400 target operating frequency depending host driver */
 	int	(*prepare_hs400_tuning)(struct mmc_host *host, struct mmc_ios *ios);
-	int	(*select_drive_strength)(unsigned int max_dtr, int host_drv, int card_drv);
+	int	(*select_drive_strength)(unsigned int max_dtr, int host_drv,
+					 int card_drv, int *drv_type);
 	void	(*hw_reset)(struct mmc_host *host);
 	void	(*card_event)(struct mmc_host *host);