From: Erick Shepherd Date: Thu, 24 Jul 2025 18:53:54 +0000 (-0500) Subject: mmc: sdhci: Disable SD card clock before changing parameters X-Git-Tag: v6.18-rc1~163^2~79 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5f755ba95ae10fd4fa28d64345056ffc18d12c5a;p=thirdparty%2Fkernel%2Fstable.git mmc: sdhci: Disable SD card clock before changing parameters Per the SD Host Controller Simplified Specification v4.20 ยง3.2.3, change the SD card clock parameters only after first disabling the external card clock. Doing this fixes a spurious clock pulse on Baytrail and Apollo Lake SD controllers which otherwise breaks voltage switching with a specific Swissbit SD card. This change is limited to Intel host controllers to avoid an issue reported on ARM64 devices. Signed-off-by: Kyle Roeschley Signed-off-by: Brad Mouring Signed-off-by: Erick Shepherd Acked-by: Adrian Hunter Link: https://lore.kernel.org/r/20250724185354.815888-1-erick.shepherd@ni.com Signed-off-by: Ulf Hansson --- diff --git a/drivers/mmc/host/sdhci-pci-core.c b/drivers/mmc/host/sdhci-pci-core.c index 826958992dfe2..47a0a738862b5 100644 --- a/drivers/mmc/host/sdhci-pci-core.c +++ b/drivers/mmc/host/sdhci-pci-core.c @@ -679,8 +679,19 @@ static int intel_start_signal_voltage_switch(struct mmc_host *mmc, return 0; } +static void sdhci_intel_set_clock(struct sdhci_host *host, unsigned int clock) +{ + u16 clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL); + + /* Stop card clock separately to avoid glitches on clock line */ + if (clk & SDHCI_CLOCK_CARD_EN) + sdhci_writew(host, clk & ~SDHCI_CLOCK_CARD_EN, SDHCI_CLOCK_CONTROL); + + sdhci_set_clock(host, clock); +} + static const struct sdhci_ops sdhci_intel_byt_ops = { - .set_clock = sdhci_set_clock, + .set_clock = sdhci_intel_set_clock, .set_power = sdhci_intel_set_power, .enable_dma = sdhci_pci_enable_dma, .set_bus_width = sdhci_set_bus_width, @@ -690,7 +701,7 @@ static const struct sdhci_ops sdhci_intel_byt_ops = { }; static const struct sdhci_ops sdhci_intel_glk_ops = { - .set_clock = sdhci_set_clock, + .set_clock = sdhci_intel_set_clock, .set_power = sdhci_intel_set_power, .enable_dma = sdhci_pci_enable_dma, .set_bus_width = sdhci_set_bus_width,