linux-kernel - [PATCH] mmc: core: Set HS clock speed before sending HS CMD13

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Message-Id: <20220310125636.1.I484f4ee35609f78b932bd50feed639c29e64997e@changeid>
Date:   Thu, 10 Mar 2022 12:56:39 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     linux-kernel@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-mmc@...r.kernel.org, Brian Norris <briannorris@...omium.org>
Subject: [PATCH] mmc: core: Set HS clock speed before sending HS CMD13

Way back in commit 4f25580fb84d ("mmc: core: changes frequency to
hs_max_dtr when selecting hs400es"), Rockchip engineers noticed that
some eMMC don't respond to SEND_STATUS commands very reliably if they're
still running at a low initial frequency. As mentioned in that commit,
JESD84-B51 P49 suggests a sequence in which the host:
1. sets HS_TIMING
2. bumps the clock ("<= 52 MHz")
3. sends further commands

It doesn't exactly require that we don't use a lower-than-52MHz
frequency, but in practice, these eMMC don't like it.

Anyway, the aforementioned commit got that right for HS400ES, but the
refactoring in 53e60650f74e ("mmc: core: Allow CMD13 polling when
switching to HS mode for mmc") messed that back up again, by reordering
step 2 after step 3.

Let's fix that, and also apply the same logic to HS200/400, where this
eMMC has problems too.

This resolves errors like this seen when booting some RK3399 Gru/Scarlet
systems:

[    2.058881] mmc1: CQHCI version 5.10
[    2.097545] mmc1: SDHCI controller on fe330000.mmc [fe330000.mmc] using ADMA
[    2.209804] mmc1: mmc_select_hs400es failed, error -84
[    2.215597] mmc1: error -84 whilst initialising MMC card
[    2.417514] mmc1: mmc_select_hs400es failed, error -110
[    2.423373] mmc1: error -110 whilst initialising MMC card
[    2.605052] mmc1: mmc_select_hs400es failed, error -110
[    2.617944] mmc1: error -110 whilst initialising MMC card
[    2.835884] mmc1: mmc_select_hs400es failed, error -110
[    2.841751] mmc1: error -110 whilst initialising MMC card

Fixes: 53e60650f74e ("mmc: core: Allow CMD13 polling when switching to HS mode for mmc")
Cc: Shawn Lin <shawn.lin@...k-chips.com>
Signed-off-by: Brian Norris <briannorris@...omium.org>
---

 drivers/mmc/core/mmc.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 13abfcd130a5..821b90caba2f 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -1390,12 +1390,17 @@ static int mmc_select_hs400es(struct mmc_card *card)
 	}
 
 	mmc_set_timing(host, MMC_TIMING_MMC_HS);
+
+	/*
+	 * Bump to HS frequency. Some cards don't handle SEND_STATUS reliably
+	 * at the initial frequency.
+	 */
+	mmc_set_clock(host, card->ext_csd.hs_max_dtr);
+
 	err = mmc_switch_status(card, true);
 	if (err)
 		goto out_err;
 
-	mmc_set_clock(host, card->ext_csd.hs_max_dtr);
-
 	/* Switch card to DDR with strobe bit */
 	val = EXT_CSD_DDR_BUS_WIDTH_8 | EXT_CSD_BUS_WIDTH_STROBE;
 	err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
@@ -1487,6 +1492,12 @@ static int mmc_select_hs200(struct mmc_card *card)
 		old_timing = host->ios.timing;
 		mmc_set_timing(host, MMC_TIMING_MMC_HS200);
 
+		/*
+		 * Bump to HS frequency. Some cards don't handle SEND_STATUS
+		 * reliably at the initial frequency.
+		 */
+		mmc_set_clock(host, card->ext_csd.hs_max_dtr);
+
 		/*
 		 * For HS200, CRC errors are not a reliable way to know the
 		 * switch failed. If there really is a problem, we would expect
-- 
2.35.1.723.g4982287a31-goog