diff mbox series

[v4,2/2] mmc: mediatek: extend number of tuning steps

Message ID 20231207063535.29546-3-axe.yang@mediatek.com (mailing list archive)
State New, archived
Headers show
Series mmc: mediatek: add support for 64-steps tuning | expand

Commit Message

Axe Yang (杨磊) Dec. 7, 2023, 6:35 a.m. UTC 
Previously, during the MSDC calibration process, a full clock cycle
actually not be covered, which in some cases didn't yield the best
results and could cause CRC errors. This problem is particularly
evident when MSDC is used as an SDIO host. In fact, MSDC support
tuning up to a maximum of 64 steps, but by default, the step number
is 32. By increase the tuning step, we are more likely to cover more
parts of a clock cycle, and get better calibration result.

To illustrate, when tuning 32 steps, if the obtained window has a hole
near the middle, like this: 0xffc07ff (hex), then the selected delay
will be the 6 (counting from right to left).

(32 <- 1)
1111 1111 1100 0000 0000 0111 11(1)1 1111

However, if we tune 64 steps, the window obtained may look like this:
0xfffffffffffc07ff. The final selected delay will be 44, which is
safer as it is further away from the hole:

(64 <- 1)
1111 ... (1)111 1111 1111 1111 1111 1100 0000 0000 0111 1111 1111

In this case, delay 6 selected through 32 steps tuning is obviously
not optimal, and this delay is closer to the hole, using it would
easily cause CRC problems.

As per mesaurements taken on mediatek SoC platform, the tuning phase
will take:
	eMMC	- 32 steps: ~3ms
		- 64 steps: ~6ms
	SDIO	- 32 steps: ~4ms
		- 64 steos: ~7ms
Tuning more steps won't prolong boot times by any meaningful amount
of time, so for SD/SDIO the default tuning steps will be adjust to
64. But for eMMC, it is still preferred to use 32 steps tuning as
otherwise there would be performance lose when accessing the RPMB
partition(requiring retuning each time).

You can configure property "mediatek,tuning-step" in MSDC dts node
to adjust the step number.

Signed-off-by: Axe Yang <axe.yang@mediatek.com>
---
 drivers/mmc/host/mtk-sd.c | 158 ++++++++++++++++++++++++++------------
 1 file changed, 110 insertions(+), 48 deletions(-)

Comments

AngeloGioacchino Del Regno Dec. 7, 2023, 12:37 p.m. UTC | #1 
Il 07/12/23 07:35, Axe Yang ha scritto:
> Previously, during the MSDC calibration process, a full clock cycle
> actually not be covered, which in some cases didn't yield the best
> results and could cause CRC errors. This problem is particularly
> evident when MSDC is used as an SDIO host. In fact, MSDC support
> tuning up to a maximum of 64 steps, but by default, the step number
> is 32. By increase the tuning step, we are more likely to cover more
> parts of a clock cycle, and get better calibration result.
> 
> To illustrate, when tuning 32 steps, if the obtained window has a hole
> near the middle, like this: 0xffc07ff (hex), then the selected delay
> will be the 6 (counting from right to left).
> 
> (32 <- 1)
> 1111 1111 1100 0000 0000 0111 11(1)1 1111
> 
> However, if we tune 64 steps, the window obtained may look like this:
> 0xfffffffffffc07ff. The final selected delay will be 44, which is
> safer as it is further away from the hole:
> 
> (64 <- 1)
> 1111 ... (1)111 1111 1111 1111 1111 1100 0000 0000 0111 1111 1111
> 
> In this case, delay 6 selected through 32 steps tuning is obviously
> not optimal, and this delay is closer to the hole, using it would
> easily cause CRC problems.
> 
> As per mesaurements taken on mediatek SoC platform, the tuning phase
> will take:
> 	eMMC	- 32 steps: ~3ms
> 		- 64 steps: ~6ms
> 	SDIO	- 32 steps: ~4ms
> 		- 64 steos: ~7ms
> Tuning more steps won't prolong boot times by any meaningful amount
> of time, so for SD/SDIO the default tuning steps will be adjust to
> 64. But for eMMC, it is still preferred to use 32 steps tuning as
> otherwise there would be performance lose when accessing the RPMB
> partition(requiring retuning each time).
> 
> You can configure property "mediatek,tuning-step" in MSDC dts node
> to adjust the step number.
> 
> Signed-off-by: Axe Yang <axe.yang@mediatek.com>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
diff mbox series

Patch

diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
index 97f7c3d4be6e..f315db48ac02 100644
--- a/drivers/mmc/host/mtk-sd.c
+++ b/drivers/mmc/host/mtk-sd.c
@@ -252,12 +252,16 @@ 
 
 #define MSDC_PAD_TUNE_DATWRDLY	  GENMASK(4, 0)		/* RW */
 #define MSDC_PAD_TUNE_DATRRDLY	  GENMASK(12, 8)	/* RW */
+#define MSDC_PAD_TUNE_DATRRDLY2	  GENMASK(12, 8)	/* RW */
 #define MSDC_PAD_TUNE_CMDRDLY	  GENMASK(20, 16)	/* RW */
+#define MSDC_PAD_TUNE_CMDRDLY2	  GENMASK(20, 16)	/* RW */
 #define MSDC_PAD_TUNE_CMDRRDLY	  GENMASK(26, 22)	/* RW */
 #define MSDC_PAD_TUNE_CLKTDLY	  GENMASK(31, 27)	/* RW */
 #define MSDC_PAD_TUNE_RXDLYSEL	  BIT(15)   /* RW */
 #define MSDC_PAD_TUNE_RD_SEL	  BIT(13)   /* RW */
 #define MSDC_PAD_TUNE_CMD_SEL	  BIT(21)   /* RW */
+#define MSDC_PAD_TUNE_RD2_SEL	  BIT(13)   /* RW */
+#define MSDC_PAD_TUNE_CMD2_SEL	  BIT(21)   /* RW */
 
 #define PAD_DS_TUNE_DLY_SEL       BIT(0)	  /* RW */
 #define PAD_DS_TUNE_DLY1	  GENMASK(6, 2)   /* RW */
@@ -325,7 +329,9 @@ 
 
 #define DEFAULT_DEBOUNCE	(8)	/* 8 cycles CD debounce */
 
-#define PAD_DELAY_MAX	32 /* PAD delay cells */
+#define TUNING_REG2_FIXED_OFFEST	4
+#define PAD_DELAY_HALF	32 /* PAD delay cells */
+#define PAD_DELAY_FULL	64
 /*--------------------------------------------------------------------------*/
 /* Descriptor Structure                                                     */
 /*--------------------------------------------------------------------------*/
@@ -461,6 +467,7 @@  struct msdc_host {
 	u32 hs400_ds_dly3;
 	u32 hs200_cmd_int_delay; /* cmd internal delay for HS200/SDR104 */
 	u32 hs400_cmd_int_delay; /* cmd internal delay for HS400 */
+	u32 tuning_step;
 	bool hs400_cmd_resp_sel_rising;
 				 /* cmd response sample selection for HS400 */
 	bool hs400_mode;	/* current eMMC will run at hs400 mode */
@@ -1615,7 +1622,7 @@  static irqreturn_t msdc_cmdq_irq(struct msdc_host *host, u32 intsts)
 	}
 
 	if (cmd_err || dat_err) {
-		dev_err(host->dev, "cmd_err = %d, dat_err =%d, intsts = 0x%x",
+		dev_err(host->dev, "cmd_err = %d, dat_err = %d, intsts = 0x%x",
 			cmd_err, dat_err, intsts);
 	}
 
@@ -1780,10 +1787,20 @@  static void msdc_init_hw(struct msdc_host *host)
 				     DATA_K_VALUE_SEL);
 			sdr_set_bits(host->top_base + EMMC_TOP_CMD,
 				     PAD_CMD_RD_RXDLY_SEL);
+			if (host->tuning_step > PAD_DELAY_HALF) {
+				sdr_set_bits(host->top_base + EMMC_TOP_CONTROL,
+					     PAD_DAT_RD_RXDLY2_SEL);
+				sdr_set_bits(host->top_base + EMMC_TOP_CMD,
+					     PAD_CMD_RD_RXDLY2_SEL);
+			}
 		} else {
 			sdr_set_bits(host->base + tune_reg,
 				     MSDC_PAD_TUNE_RD_SEL |
 				     MSDC_PAD_TUNE_CMD_SEL);
+			if (host->tuning_step > PAD_DELAY_HALF)
+				sdr_set_bits(host->base + tune_reg + TUNING_REG2_FIXED_OFFEST,
+					     MSDC_PAD_TUNE_RD2_SEL |
+					     MSDC_PAD_TUNE_CMD2_SEL);
 		}
 	} else {
 		/* choose clock tune */
@@ -1925,24 +1942,24 @@  static void msdc_ops_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 		msdc_set_mclk(host, ios->timing, ios->clock);
 }
 
-static u32 test_delay_bit(u32 delay, u32 bit)
+static u64 test_delay_bit(u64 delay, u32 bit)
 {
-	bit %= PAD_DELAY_MAX;
-	return delay & BIT(bit);
+	bit %= PAD_DELAY_FULL;
+	return delay & BIT_ULL(bit);
 }
 
-static int get_delay_len(u32 delay, u32 start_bit)
+static int get_delay_len(u64 delay, u32 start_bit)
 {
 	int i;
 
-	for (i = 0; i < (PAD_DELAY_MAX - start_bit); i++) {
+	for (i = 0; i < (PAD_DELAY_FULL - start_bit); i++) {
 		if (test_delay_bit(delay, start_bit + i) == 0)
 			return i;
 	}
-	return PAD_DELAY_MAX - start_bit;
+	return PAD_DELAY_FULL - start_bit;
 }
 
-static struct msdc_delay_phase get_best_delay(struct msdc_host *host, u32 delay)
+static struct msdc_delay_phase get_best_delay(struct msdc_host *host, u64 delay)
 {
 	int start = 0, len = 0;
 	int start_final = 0, len_final = 0;
@@ -1950,28 +1967,28 @@  static struct msdc_delay_phase get_best_delay(struct msdc_host *host, u32 delay)
 	struct msdc_delay_phase delay_phase = { 0, };
 
 	if (delay == 0) {
-		dev_err(host->dev, "phase error: [map:%x]\n", delay);
+		dev_err(host->dev, "phase error: [map:%016llx]\n", delay);
 		delay_phase.final_phase = final_phase;
 		return delay_phase;
 	}
 
-	while (start < PAD_DELAY_MAX) {
+	while (start < PAD_DELAY_FULL) {
 		len = get_delay_len(delay, start);
 		if (len_final < len) {
 			start_final = start;
 			len_final = len;
 		}
 		start += len ? len : 1;
-		if (len >= 12 && start_final < 4)
+		if (!upper_32_bits(delay) && len >= 12 && start_final < 4)
 			break;
 	}
 
 	/* The rule is that to find the smallest delay cell */
 	if (start_final == 0)
-		final_phase = (start_final + len_final / 3) % PAD_DELAY_MAX;
+		final_phase = (start_final + len_final / 3) % PAD_DELAY_FULL;
 	else
-		final_phase = (start_final + len_final / 2) % PAD_DELAY_MAX;
-	dev_dbg(host->dev, "phase: [map:%x] [maxlen:%d] [final:%d]\n",
+		final_phase = (start_final + len_final / 2) % PAD_DELAY_FULL;
+	dev_dbg(host->dev, "phase: [map:%016llx] [maxlen:%d] [final:%d]\n",
 		delay, len_final, final_phase);
 
 	delay_phase.maxlen = len_final;
@@ -1984,30 +2001,64 @@  static inline void msdc_set_cmd_delay(struct msdc_host *host, u32 value)
 {
 	u32 tune_reg = host->dev_comp->pad_tune_reg;
 
-	if (host->top_base)
-		sdr_set_field(host->top_base + EMMC_TOP_CMD, PAD_CMD_RXDLY,
-			      value);
-	else
-		sdr_set_field(host->base + tune_reg, MSDC_PAD_TUNE_CMDRDLY,
-			      value);
+	if (host->top_base) {
+		if (value < PAD_DELAY_HALF) {
+			sdr_set_field(host->top_base + EMMC_TOP_CMD, PAD_CMD_RXDLY, value);
+			sdr_set_field(host->top_base + EMMC_TOP_CMD, PAD_CMD_RXDLY2, 0);
+		} else {
+			sdr_set_field(host->top_base + EMMC_TOP_CMD, PAD_CMD_RXDLY,
+				      PAD_DELAY_HALF - 1);
+			sdr_set_field(host->top_base + EMMC_TOP_CMD, PAD_CMD_RXDLY2,
+				      value - PAD_DELAY_HALF);
+		}
+	} else {
+		if (value < PAD_DELAY_HALF) {
+			sdr_set_field(host->base + tune_reg, MSDC_PAD_TUNE_CMDRDLY, value);
+			sdr_set_field(host->base + tune_reg + TUNING_REG2_FIXED_OFFEST,
+				      MSDC_PAD_TUNE_CMDRDLY2, 0);
+		} else {
+			sdr_set_field(host->base + tune_reg, MSDC_PAD_TUNE_CMDRDLY,
+				      PAD_DELAY_HALF - 1);
+			sdr_set_field(host->base + tune_reg + TUNING_REG2_FIXED_OFFEST,
+				      MSDC_PAD_TUNE_CMDRDLY2, value - PAD_DELAY_HALF);
+		}
+	}
 }
 
 static inline void msdc_set_data_delay(struct msdc_host *host, u32 value)
 {
 	u32 tune_reg = host->dev_comp->pad_tune_reg;
 
-	if (host->top_base)
-		sdr_set_field(host->top_base + EMMC_TOP_CONTROL,
-			      PAD_DAT_RD_RXDLY, value);
-	else
-		sdr_set_field(host->base + tune_reg, MSDC_PAD_TUNE_DATRRDLY,
-			      value);
+	if (host->top_base) {
+		if (value < PAD_DELAY_HALF) {
+			sdr_set_field(host->top_base + EMMC_TOP_CONTROL,
+				      PAD_DAT_RD_RXDLY, value);
+			sdr_set_field(host->top_base + EMMC_TOP_CONTROL,
+				      PAD_DAT_RD_RXDLY2, 0);
+		} else {
+			sdr_set_field(host->top_base + EMMC_TOP_CONTROL,
+				      PAD_DAT_RD_RXDLY, PAD_DELAY_HALF - 1);
+			sdr_set_field(host->top_base + EMMC_TOP_CONTROL,
+				      PAD_DAT_RD_RXDLY2, value - PAD_DELAY_HALF);
+		}
+	} else {
+		if (value < PAD_DELAY_HALF) {
+			sdr_set_field(host->base + tune_reg, MSDC_PAD_TUNE_DATRRDLY, value);
+			sdr_set_field(host->base + tune_reg + TUNING_REG2_FIXED_OFFEST,
+				      MSDC_PAD_TUNE_DATRRDLY2, 0);
+		} else {
+			sdr_set_field(host->base + tune_reg, MSDC_PAD_TUNE_DATRRDLY,
+				      PAD_DELAY_HALF - 1);
+			sdr_set_field(host->base + tune_reg + TUNING_REG2_FIXED_OFFEST,
+				      MSDC_PAD_TUNE_DATRRDLY2, value - PAD_DELAY_HALF);
+		}
+	}
 }
 
 static int msdc_tune_response(struct mmc_host *mmc, u32 opcode)
 {
 	struct msdc_host *host = mmc_priv(mmc);
-	u32 rise_delay = 0, fall_delay = 0;
+	u64 rise_delay = 0, fall_delay = 0;
 	struct msdc_delay_phase final_rise_delay, final_fall_delay = { 0,};
 	struct msdc_delay_phase internal_delay_phase;
 	u8 final_delay, final_maxlen;
@@ -2023,7 +2074,7 @@  static int msdc_tune_response(struct mmc_host *mmc, u32 opcode)
 			      host->hs200_cmd_int_delay);
 
 	sdr_clr_bits(host->base + MSDC_IOCON, MSDC_IOCON_RSPL);
-	for (i = 0 ; i < PAD_DELAY_MAX; i++) {
+	for (i = 0; i < host->tuning_step; i++) {
 		msdc_set_cmd_delay(host, i);
 		/*
 		 * Using the same parameters, it may sometimes pass the test,
@@ -2033,9 +2084,9 @@  static int msdc_tune_response(struct mmc_host *mmc, u32 opcode)
 		for (j = 0; j < 3; j++) {
 			mmc_send_tuning(mmc, opcode, &cmd_err);
 			if (!cmd_err) {
-				rise_delay |= BIT(i);
+				rise_delay |= BIT_ULL(i);
 			} else {
-				rise_delay &= ~BIT(i);
+				rise_delay &= ~BIT_ULL(i);
 				break;
 			}
 		}
@@ -2047,7 +2098,7 @@  static int msdc_tune_response(struct mmc_host *mmc, u32 opcode)
 		goto skip_fall;
 
 	sdr_set_bits(host->base + MSDC_IOCON, MSDC_IOCON_RSPL);
-	for (i = 0; i < PAD_DELAY_MAX; i++) {
+	for (i = 0; i < host->tuning_step; i++) {
 		msdc_set_cmd_delay(host, i);
 		/*
 		 * Using the same parameters, it may sometimes pass the test,
@@ -2057,9 +2108,9 @@  static int msdc_tune_response(struct mmc_host *mmc, u32 opcode)
 		for (j = 0; j < 3; j++) {
 			mmc_send_tuning(mmc, opcode, &cmd_err);
 			if (!cmd_err) {
-				fall_delay |= BIT(i);
+				fall_delay |= BIT_ULL(i);
 			} else {
-				fall_delay &= ~BIT(i);
+				fall_delay &= ~BIT_ULL(i);
 				break;
 			}
 		}
@@ -2082,12 +2133,12 @@  static int msdc_tune_response(struct mmc_host *mmc, u32 opcode)
 	if (host->dev_comp->async_fifo || host->hs200_cmd_int_delay)
 		goto skip_internal;
 
-	for (i = 0; i < PAD_DELAY_MAX; i++) {
+	for (i = 0; i < host->tuning_step; i++) {
 		sdr_set_field(host->base + tune_reg,
 			      MSDC_PAD_TUNE_CMDRRDLY, i);
 		mmc_send_tuning(mmc, opcode, &cmd_err);
 		if (!cmd_err)
-			internal_delay |= BIT(i);
+			internal_delay |= BIT_ULL(i);
 	}
 	dev_dbg(host->dev, "Final internal delay: 0x%x\n", internal_delay);
 	internal_delay_phase = get_best_delay(host, internal_delay);
@@ -2121,7 +2172,8 @@  static int hs400_tune_response(struct mmc_host *mmc, u32 opcode)
 		sdr_clr_bits(host->base + MSDC_IOCON, MSDC_IOCON_RSPL);
 	else
 		sdr_set_bits(host->base + MSDC_IOCON, MSDC_IOCON_RSPL);
-	for (i = 0 ; i < PAD_DELAY_MAX; i++) {
+
+	for (i = 0; i < PAD_DELAY_HALF; i++) {
 		sdr_set_field(host->base + PAD_CMD_TUNE,
 			      PAD_CMD_TUNE_RX_DLY3, i);
 		/*
@@ -2151,7 +2203,7 @@  static int hs400_tune_response(struct mmc_host *mmc, u32 opcode)
 static int msdc_tune_data(struct mmc_host *mmc, u32 opcode)
 {
 	struct msdc_host *host = mmc_priv(mmc);
-	u32 rise_delay = 0, fall_delay = 0;
+	u64 rise_delay = 0, fall_delay = 0;
 	struct msdc_delay_phase final_rise_delay, final_fall_delay = { 0,};
 	u8 final_delay, final_maxlen;
 	int i, ret;
@@ -2160,11 +2212,11 @@  static int msdc_tune_data(struct mmc_host *mmc, u32 opcode)
 		      host->latch_ck);
 	sdr_clr_bits(host->base + MSDC_IOCON, MSDC_IOCON_DSPL);
 	sdr_clr_bits(host->base + MSDC_IOCON, MSDC_IOCON_W_DSPL);
-	for (i = 0 ; i < PAD_DELAY_MAX; i++) {
+	for (i = 0; i < host->tuning_step; i++) {
 		msdc_set_data_delay(host, i);
 		ret = mmc_send_tuning(mmc, opcode, NULL);
 		if (!ret)
-			rise_delay |= BIT(i);
+			rise_delay |= BIT_ULL(i);
 	}
 	final_rise_delay = get_best_delay(host, rise_delay);
 	/* if rising edge has enough margin, then do not scan falling edge */
@@ -2174,11 +2226,11 @@  static int msdc_tune_data(struct mmc_host *mmc, u32 opcode)
 
 	sdr_set_bits(host->base + MSDC_IOCON, MSDC_IOCON_DSPL);
 	sdr_set_bits(host->base + MSDC_IOCON, MSDC_IOCON_W_DSPL);
-	for (i = 0; i < PAD_DELAY_MAX; i++) {
+	for (i = 0; i < host->tuning_step; i++) {
 		msdc_set_data_delay(host, i);
 		ret = mmc_send_tuning(mmc, opcode, NULL);
 		if (!ret)
-			fall_delay |= BIT(i);
+			fall_delay |= BIT_ULL(i);
 	}
 	final_fall_delay = get_best_delay(host, fall_delay);
 
@@ -2206,7 +2258,7 @@  static int msdc_tune_data(struct mmc_host *mmc, u32 opcode)
 static int msdc_tune_together(struct mmc_host *mmc, u32 opcode)
 {
 	struct msdc_host *host = mmc_priv(mmc);
-	u32 rise_delay = 0, fall_delay = 0;
+	u64 rise_delay = 0, fall_delay = 0;
 	struct msdc_delay_phase final_rise_delay, final_fall_delay = { 0,};
 	u8 final_delay, final_maxlen;
 	int i, ret;
@@ -2217,12 +2269,12 @@  static int msdc_tune_together(struct mmc_host *mmc, u32 opcode)
 	sdr_clr_bits(host->base + MSDC_IOCON, MSDC_IOCON_RSPL);
 	sdr_clr_bits(host->base + MSDC_IOCON,
 		     MSDC_IOCON_DSPL | MSDC_IOCON_W_DSPL);
-	for (i = 0 ; i < PAD_DELAY_MAX; i++) {
+	for (i = 0; i < host->tuning_step; i++) {
 		msdc_set_cmd_delay(host, i);
 		msdc_set_data_delay(host, i);
 		ret = mmc_send_tuning(mmc, opcode, NULL);
 		if (!ret)
-			rise_delay |= BIT(i);
+			rise_delay |= BIT_ULL(i);
 	}
 	final_rise_delay = get_best_delay(host, rise_delay);
 	/* if rising edge has enough margin, then do not scan falling edge */
@@ -2233,12 +2285,12 @@  static int msdc_tune_together(struct mmc_host *mmc, u32 opcode)
 	sdr_set_bits(host->base + MSDC_IOCON, MSDC_IOCON_RSPL);
 	sdr_set_bits(host->base + MSDC_IOCON,
 		     MSDC_IOCON_DSPL | MSDC_IOCON_W_DSPL);
-	for (i = 0; i < PAD_DELAY_MAX; i++) {
+	for (i = 0; i < host->tuning_step; i++) {
 		msdc_set_cmd_delay(host, i);
 		msdc_set_data_delay(host, i);
 		ret = mmc_send_tuning(mmc, opcode, NULL);
 		if (!ret)
-			fall_delay |= BIT(i);
+			fall_delay |= BIT_ULL(i);
 	}
 	final_fall_delay = get_best_delay(host, fall_delay);
 
@@ -2346,7 +2398,7 @@  static int msdc_execute_hs400_tuning(struct mmc_host *mmc, struct mmc_card *card
 	}
 
 	host->hs400_tuning = true;
-	for (i = 0; i < PAD_DELAY_MAX; i++) {
+	for (i = 0; i < PAD_DELAY_HALF; i++) {
 		if (host->top_base)
 			sdr_set_field(host->top_base + EMMC50_PAD_DS_TUNE,
 				      PAD_DS_DLY1, i);
@@ -2580,6 +2632,8 @@  static const struct cqhci_host_ops msdc_cmdq_ops = {
 static void msdc_of_property_parse(struct platform_device *pdev,
 				   struct msdc_host *host)
 {
+	struct mmc_host *mmc = mmc_from_priv(host);
+
 	of_property_read_u32(pdev->dev.of_node, "mediatek,latch-ck",
 			     &host->latch_ck);
 
@@ -2601,6 +2655,14 @@  static void msdc_of_property_parse(struct platform_device *pdev,
 	else
 		host->hs400_cmd_resp_sel_rising = false;
 
+	if (of_property_read_u32(pdev->dev.of_node, "mediatek,tuning-step",
+				 &host->tuning_step)) {
+		if (mmc->caps2 & MMC_CAP2_NO_MMC)
+			host->tuning_step = PAD_DELAY_FULL;
+		else
+			host->tuning_step = PAD_DELAY_HALF;
+	}
+
 	if (of_property_read_bool(pdev->dev.of_node,
 				  "supports-cqe"))
 		host->cqhci = true;