5 files changed, 45 insertions, 0 deletions
diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 95cceae96944..d572b2beb65a 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -452,6 +452,14 @@ int mmc_of_parse(struct mmc_host *host)
 	if (of_find_property(np, "mmc-hs400-1_2v", &len))
 		host->caps2 |= MMC_CAP2_HS400_1_2V | MMC_CAP2_HS200_1_2V_SDR;
 
+	host->dsr_req = !of_property_read_u32(np, "dsr", &host->dsr);
+	if (host->dsr_req && (host->dsr & ~0xffff)) {
+		dev_err(host->parent,
+			"device tree specified broken value for DSR: 0x%x, ignoring\n",
+			host->dsr);
+		host->dsr_req = 0;
+	}
+
 	return 0;
 
 out:
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 1eda8dd8c867..31c43165f8bc 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -162,6 +162,7 @@ static int mmc_decode_csd(struct mmc_card *card)
 	csd->read_partial = UNSTUFF_BITS(resp, 79, 1);
 	csd->write_misalign = UNSTUFF_BITS(resp, 78, 1);
 	csd->read_misalign = UNSTUFF_BITS(resp, 77, 1);
+	csd->dsr_imp = UNSTUFF_BITS(resp, 76, 1);
 	csd->r2w_factor = UNSTUFF_BITS(resp, 26, 3);
 	csd->write_blkbits = UNSTUFF_BITS(resp, 22, 4);
 	csd->write_partial = UNSTUFF_BITS(resp, 21, 1);
@@ -1272,6 +1273,13 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 	}
 
 	/*
+	 * handling only for cards supporting DSR and hosts requesting
+	 * DSR configuration
+	 */
+	if (card->csd.dsr_imp && host->dsr_req)
+		mmc_set_dsr(host);
+
+	/*
 	 * Select card, as all following commands rely on that.
 	 */
 	if (!mmc_host_is_spi(host)) {
diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
index f51b5ba3bbea..ba0275e90617 100644
--- a/drivers/mmc/core/mmc_ops.c
+++ b/drivers/mmc/core/mmc_ops.c
@@ -93,6 +93,26 @@ int mmc_deselect_cards(struct mmc_host *host)
 	return _mmc_select_card(host, NULL);
 }
 
+/*
+ * Write the value specified in the device tree or board code into the optional
+ * 16 bit Driver Stage Register. This can be used to tune raise/fall times and
+ * drive strength of the DAT and CMD outputs. The actual meaning of a given
+ * value is hardware dependant.
+ * The presence of the DSR register can be determined from the CSD register,
+ * bit 76.
+ */
+int mmc_set_dsr(struct mmc_host *host)
+{
+	struct mmc_command cmd = {0};
+
+	cmd.opcode = MMC_SET_DSR;
+
+	cmd.arg = (host->dsr << 16) | 0xffff;
+	cmd.flags = MMC_RSP_NONE | MMC_CMD_AC;
+
+	return mmc_wait_for_cmd(host, &cmd, MMC_CMD_RETRIES);
+}
+
 int mmc_go_idle(struct mmc_host *host)
 {
 	int err;
diff --git a/drivers/mmc/core/mmc_ops.h b/drivers/mmc/core/mmc_ops.h
index 80ae9f4e0293..390dac665b2a 100644
--- a/drivers/mmc/core/mmc_ops.h
+++ b/drivers/mmc/core/mmc_ops.h
@@ -14,6 +14,7 @@
 
 int mmc_select_card(struct mmc_card *card);
 int mmc_deselect_cards(struct mmc_host *host);
+int mmc_set_dsr(struct mmc_host *host);
 int mmc_go_idle(struct mmc_host *host);
 int mmc_send_op_cond(struct mmc_host *host, u32 ocr, u32 *rocr);
 int mmc_all_send_cid(struct mmc_host *host, u32 *cid);
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 0c44510bf717..25913889cbaa 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -127,6 +127,7 @@ static int mmc_decode_csd(struct mmc_card *card)
 		csd->read_partial = UNSTUFF_BITS(resp, 79, 1);
 		csd->write_misalign = UNSTUFF_BITS(resp, 78, 1);
 		csd->read_misalign = UNSTUFF_BITS(resp, 77, 1);
+		csd->dsr_imp = UNSTUFF_BITS(resp, 76, 1);
 		csd->r2w_factor = UNSTUFF_BITS(resp, 26, 3);
 		csd->write_blkbits = UNSTUFF_BITS(resp, 22, 4);
 		csd->write_partial = UNSTUFF_BITS(resp, 21, 1);
@@ -954,6 +955,13 @@ static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
 	}
 
 	/*
+	 * handling only for cards supporting DSR and hosts requesting
+	 * DSR configuration
+	 */
+	if (card->csd.dsr_imp && host->dsr_req)
+		mmc_set_dsr(host);
+
+	/*
 	 * Select card, as all following commands rely on that.
 	 */
 	if (!mmc_host_is_spi(host)) {