[PATCH v2] mmc: renesas_sdhi: Fix change point of data handling

[Claudiu]

From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>

On latest kernel revisions it has been noticed (on a RZ/G3S system) that
when booting Linux and root file system is on eMMC, at some point in
the booting process, when the systemd applications are started, the
"mmc0: tuning execution failed: -5" message is displayed on console.
On kernel v6.7-rc5 this is reproducible in 90% of the boots. This was
missing on the same system with kernel v6.5.0-rc1. It was also noticed on
kernel revisions v6.6-rcX on a RZ/G2UL based system but not on the kernel
this fix is based on (v6.7-rc5).

Investigating it on RZ/G3S lead to the conclusion that every time the issue
is reproduced all the probed TAPs are OK. According to datasheet, when this
happens the change point of data need to be considered for tuning.

Previous code considered the change point of data happens when the content
of the SMPCMP register is zero. According to RZ/V2M hardware manual,
chapter "Change Point of the Input Data" (as this is the most clear
description that I've found about change point of the input data and all
RZ hardware manual are similar on this chapter), at the time of tuning,
data is captured by the previous and next TAPs and the result is stored in
the SMPCMP register (previous TAP in bits 22..16, next TAP in bits 7..0).
If there is a mismatch b/w the previous and the next TAPs, it indicates
that there is a change point of the input data.

To comply with this, the code checks if this mismatch is present and
updates the priv->smpcmp mask.

This change has been checked on the devices with the following DTSes by
doing 50 consecutive reboots and checking for the tuning failure message:
- r9a08g045s33-smarc.dts
- r8a7742-iwg21d-q7.dts
- r8a7743-iwg20d-q7.dts
- r8a7744-iwg20d-q7.dts
- r8a7745-iwg22d-sodimm.dts
- r8a77470-iwg23s-sbc.dts
- r8a774a1-hihope-rzg2m-ex.dts
- r8a774b1-hihope-rzg2n-ex.dts
- r8a774c0-ek874.dts
- r8a774e1-hihope-rzg2h-ex.dts
- r9a07g043u11-smarc-rzg2ul.dts
- r9a07g044c2-smarc-rzg2lc.dts
- r9a07g044l2-smarc-rzg2l.dts
- r9a07g054l2-smarc-rzv2l.dts

On r8a774a1-hihope-rzg2m-ex, even though the hardware manual doesn't say
anything special about it in the "Change Point of the Input Data" chapter
or SMPCMP register description, it has been noticed that although all TAPs
probed in the tuning process are OK the SMPCMP is zero. For this updated
the renesas_sdhi_select_tuning() function to use priv->taps in case all
TAPs are OK.

Fixes: 5fb6bf51f6d1 ("mmc: renesas_sdhi: improve TAP selection if all TAPs are good")
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
---

Changes in v2:
- read the SH_MOBILE_SDHI_SCC_SMPCMP register only on success path of
  mmc_send_tuning()

 drivers/mmc/host/renesas_sdhi_core.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/mmc/host/renesas_sdhi_core.c b/drivers/mmc/host/renesas_sdhi_core.c
index c675dec587ef..0090228a5e8f 100644
--- a/drivers/mmc/host/renesas_sdhi_core.c
+++ b/drivers/mmc/host/renesas_sdhi_core.c
@@ -18,6 +18,7 @@
  *
  */
 
+#include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/iopoll.h>
@@ -312,6 +313,8 @@ static int renesas_sdhi_start_signal_voltage_switch(struct mmc_host *mmc,
 #define SH_MOBILE_SDHI_SCC_SMPCMP_CMD_REQDOWN	BIT(8)
 #define SH_MOBILE_SDHI_SCC_SMPCMP_CMD_REQUP	BIT(24)
 #define SH_MOBILE_SDHI_SCC_SMPCMP_CMD_ERR	(BIT(8) | BIT(24))
+#define SH_MOBILE_SDHI_SCC_SMPCMP_CMPNGU_DATA	GENMASK(23, 16)
+#define SH_MOBILE_SDHI_SCC_SMPCMP_CMPNGD_DATA	GENMASK(7, 0)
 
 #define SH_MOBILE_SDHI_SCC_TMPPORT2_HS400OSEL	BIT(4)
 #define SH_MOBILE_SDHI_SCC_TMPPORT2_HS400EN	BIT(31)
@@ -641,7 +644,14 @@ static int renesas_sdhi_select_tuning(struct tmio_mmc_host *host)
 	 * identifying the change point of data.
 	 */
 	if (bitmap_full(priv->taps, taps_size)) {
-		bitmap = priv->smpcmp;
+		/*
+		 * On some setups it happens that all TAPS are OK but
+		 * no change point of data. Any tap should be OK for this.
+		 */
+		if (bitmap_empty(priv->smpcmp, taps_size))
+			bitmap = priv->taps;
+		else
+			bitmap = priv->smpcmp;
 		min_tap_row = 1;
 	} else {
 		bitmap = priv->taps;
@@ -706,11 +716,18 @@ static int renesas_sdhi_execute_tuning(struct mmc_host *mmc, u32 opcode)
 		if (mmc_send_tuning(mmc, opcode, &cmd_error) == 0)
 			set_bit(i, priv->taps);
 
-		if (sd_scc_read32(host, priv, SH_MOBILE_SDHI_SCC_SMPCMP) == 0)
-			set_bit(i, priv->smpcmp);
-
-		if (cmd_error)
+		if (cmd_error) {
 			mmc_send_abort_tuning(mmc, opcode);
+		} else {
+			u32 val, cmpngu_data, cmpngd_data;
+
+			val = sd_scc_read32(host, priv, SH_MOBILE_SDHI_SCC_SMPCMP);
+			cmpngu_data = FIELD_GET(SH_MOBILE_SDHI_SCC_SMPCMP_CMPNGU_DATA, val);
+			cmpngd_data = FIELD_GET(SH_MOBILE_SDHI_SCC_SMPCMP_CMPNGD_DATA, val);
+
+			if (cmpngu_data != cmpngd_data)
+				set_bit(i, priv->smpcmp);
+		}
 	}
 
 	ret = renesas_sdhi_select_tuning(host);
-- 
2.39.2