mmc: sd: set current limit for uhs cards

We decide on the current limit to be set for the card based on the
Capability of Host Controller to provide current at 1.8V signalling,
and the maximum current limit of the card as indicated by CMD6
mode 0. We then set the current limit for the card using CMD6 mode 1.
As per the Physical Layer Spec v3.01, the current limit switch is
only applicable for SDR50, SDR104, and DDR50 bus speed modes. For
other UHS-I modes, we set the default current limit of 200mA.

Tested by Zhangfei Gao with a Toshiba uhs card and general hs card,
on mmp2 in SDMA mode.

Signed-off-by: Arindam Nath <arindam.nath@amd.com>
Reviewed-by: Philip Rakity <prakity@marvell.com>
Tested-by: Philip Rakity <prakity@marvell.com>
Acked-by: Zhangfei Gao <zhangfei.gao@marvell.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

2 files changed, 73 insertions, 0 deletions

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 6970b82..8e2d801 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -512,6 +512,64 @@ static int sd_set_bus_speed_mode(struct mmc_card *card, u8 *status)
 	return 0;
 }
 
+static int sd_set_current_limit(struct mmc_card *card, u8 *status)
+{
+	int current_limit = 0;
+	int err;
+
+	/*
+	 * Current limit switch is only defined for SDR50, SDR104, and DDR50
+	 * bus speed modes. For other bus speed modes, we set the default
+	 * current limit of 200mA.
+	 */
+	if ((card->sd_bus_speed == UHS_SDR50_BUS_SPEED) ||
+	    (card->sd_bus_speed == UHS_SDR104_BUS_SPEED) ||
+	    (card->sd_bus_speed == UHS_DDR50_BUS_SPEED)) {
+		if (card->host->caps & MMC_CAP_MAX_CURRENT_800) {
+			if (card->sw_caps.sd3_curr_limit & SD_MAX_CURRENT_800)
+				current_limit = SD_SET_CURRENT_LIMIT_800;
+			else if (card->sw_caps.sd3_curr_limit &
+					SD_MAX_CURRENT_600)
+				current_limit = SD_SET_CURRENT_LIMIT_600;
+			else if (card->sw_caps.sd3_curr_limit &
+					SD_MAX_CURRENT_400)
+				current_limit = SD_SET_CURRENT_LIMIT_400;
+			else if (card->sw_caps.sd3_curr_limit &
+					SD_MAX_CURRENT_200)
+				current_limit = SD_SET_CURRENT_LIMIT_200;
+		} else if (card->host->caps & MMC_CAP_MAX_CURRENT_600) {
+			if (card->sw_caps.sd3_curr_limit & SD_MAX_CURRENT_600)
+				current_limit = SD_SET_CURRENT_LIMIT_600;
+			else if (card->sw_caps.sd3_curr_limit &
+					SD_MAX_CURRENT_400)
+				current_limit = SD_SET_CURRENT_LIMIT_400;
+			else if (card->sw_caps.sd3_curr_limit &
+					SD_MAX_CURRENT_200)
+				current_limit = SD_SET_CURRENT_LIMIT_200;
+		} else if (card->host->caps & MMC_CAP_MAX_CURRENT_400) {
+			if (card->sw_caps.sd3_curr_limit & SD_MAX_CURRENT_400)
+				current_limit = SD_SET_CURRENT_LIMIT_400;
+			else if (card->sw_caps.sd3_curr_limit &
+					SD_MAX_CURRENT_200)
+				current_limit = SD_SET_CURRENT_LIMIT_200;
+		} else if (card->host->caps & MMC_CAP_MAX_CURRENT_200) {
+			if (card->sw_caps.sd3_curr_limit & SD_MAX_CURRENT_200)
+				current_limit = SD_SET_CURRENT_LIMIT_200;
+		}
+	} else
+		current_limit = SD_SET_CURRENT_LIMIT_200;
+
+	err = mmc_sd_switch(card, 1, 3, current_limit, status);
+	if (err)
+		return err;
+
+	if (((status[15] >> 4) & 0x0F) != current_limit)
+		printk(KERN_WARNING "%s: Problem setting current limit!\n",
+			mmc_hostname(card->host));
+
+	return 0;
+}
+
 /*
  * UHS-I specific initialization procedure
  */
@@ -550,6 +608,11 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card)
 
 	/* Set bus speed mode of the card */
 	err = sd_set_bus_speed_mode(card, status);
+	if (err)
+		goto out;
+
+	/* Set current limit for the card */
+	err = sd_set_current_limit(card, status);
 
 out:
 	kfree(status);
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 8994493..2a15aad 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2216,6 +2216,16 @@ int sdhci_add_host(struct sdhci_host *host)
 
 		if (max_current_180 > 150)
 			mmc->caps |= MMC_CAP_SET_XPC_180;
+
+		/* Maximum current capabilities of the host at 1.8V */
+		if (max_current_180 >= 800)
+			mmc->caps |= MMC_CAP_MAX_CURRENT_800;
+		else if (max_current_180 >= 600)
+			mmc->caps |= MMC_CAP_MAX_CURRENT_600;
+		else if (max_current_180 >= 400)
+			mmc->caps |= MMC_CAP_MAX_CURRENT_400;
+		else
+			mmc->caps |= MMC_CAP_MAX_CURRENT_200;
 	}
 
 	mmc->ocr_avail = ocr_avail;