The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From c9107dd0b851777d7e134420baf13a5c5343bc16 Mon Sep 17 00:00:00 2001 From: Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx> Date: Sat, 7 Aug 2021 13:06:35 +0200 Subject: [PATCH] mmc: sdhci-iproc: Cap min clock frequency on BCM2711 There is a known bug on BCM2711's SDHCI core integration where the controller will hang when the difference between the core clock and the bus clock is too great. Specifically this can be reproduced under the following conditions: - No SD card plugged in, polling thread is running, probing cards at 100 kHz. - BCM2711's core clock configured at 500MHz or more. So set 200 kHz as the minimum clock frequency available for that board. For more information on the issue see this: https://lore.kernel.org/linux-mmc/20210322185816.27582-1-nsaenz@xxxxxxxxxx/T/#m11f2783a09b581da6b8a15f302625b43a6ecdeca Fixes: f84e411c85be ("mmc: sdhci-iproc: Add support for emmc2 of the BCM2711") Signed-off-by: Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx> Signed-off-by: Stefan Wahren <stefan.wahren@xxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/1628334401-6577-5-git-send-email-stefan.wahren@xxxxxxxx Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx> --- drivers/mmc/host/sdhci-iproc.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/mmc/host/sdhci-iproc.c b/drivers/mmc/host/sdhci-iproc.c index cce390fe9cf3..032bf852397f 100644 --- a/drivers/mmc/host/sdhci-iproc.c +++ b/drivers/mmc/host/sdhci-iproc.c @@ -173,6 +173,23 @@ static unsigned int sdhci_iproc_get_max_clock(struct sdhci_host *host) return pltfm_host->clock; } +/* + * There is a known bug on BCM2711's SDHCI core integration where the + * controller will hang when the difference between the core clock and the bus + * clock is too great. Specifically this can be reproduced under the following + * conditions: + * + * - No SD card plugged in, polling thread is running, probing cards at + * 100 kHz. + * - BCM2711's core clock configured at 500MHz or more + * + * So we set 200kHz as the minimum clock frequency available for that SoC. + */ +static unsigned int sdhci_iproc_bcm2711_get_min_clock(struct sdhci_host *host) +{ + return 200000; +} + static const struct sdhci_ops sdhci_iproc_ops = { .set_clock = sdhci_set_clock, .get_max_clock = sdhci_iproc_get_max_clock, @@ -271,6 +288,7 @@ static const struct sdhci_ops sdhci_iproc_bcm2711_ops = { .set_clock = sdhci_set_clock, .set_power = sdhci_set_power_and_bus_voltage, .get_max_clock = sdhci_iproc_get_max_clock, + .get_min_clock = sdhci_iproc_bcm2711_get_min_clock, .set_bus_width = sdhci_set_bus_width, .reset = sdhci_reset, .set_uhs_signaling = sdhci_set_uhs_signaling, -- 2.30.2
