This is a note to let you know that I've just added the patch titled
mmc: jz4740: Work around bug on JZ4760(B)
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mmc-jz4740-work-around-bug-on-jz4760-b.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3f18c5046e633cc4bbad396b74c05d46d353033d Mon Sep 17 00:00:00 2001
From: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
Date: Tue, 31 Jan 2023 21:02:28 +0000
Subject: mmc: jz4740: Work around bug on JZ4760(B)
From: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
commit 3f18c5046e633cc4bbad396b74c05d46d353033d upstream.
On JZ4760 and JZ4760B, SD cards fail to run if the maximum clock
rate is set to 50 MHz, even though the controller officially does
support it.
Until the actual bug is found and fixed, limit the maximum clock rate to
24 MHz.
Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20230131210229.68129-1-paul@xxxxxxxxxxxxxxx
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/mmc/host/jz4740_mmc.c | 10 ++++++++++
1 file changed, 10 insertions(+)
--- a/drivers/mmc/host/jz4740_mmc.c
+++ b/drivers/mmc/host/jz4740_mmc.c
@@ -1082,6 +1082,16 @@ static int jz4740_mmc_probe(struct platf
mmc->ops = &jz4740_mmc_ops;
if (!mmc->f_max)
mmc->f_max = JZ_MMC_CLK_RATE;
+
+ /*
+ * There seems to be a problem with this driver on the JZ4760 and
+ * JZ4760B SoCs. There, when using the maximum rate supported (50 MHz),
+ * the communication fails with many SD cards.
+ * Until this bug is sorted out, limit the maximum rate to 24 MHz.
+ */
+ if (host->version == JZ_MMC_JZ4760 && mmc->f_max > JZ_MMC_CLK_RATE)
+ mmc->f_max = JZ_MMC_CLK_RATE;
+
mmc->f_min = mmc->f_max / 128;
mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34;
Patches currently in stable-queue which might be from paul@xxxxxxxxxxxxxxx are
queue-4.19/mmc-jz4740-work-around-bug-on-jz4760-b.patch
