[PATCH V5 3/4] mmc: core: Introduce a new flag max-sd-hs-hz
From: Sarthak Garg <hidden>
Date: 2025-09-03 08:04:24
Also in:
linux-arm-msm, linux-mmc, lkml
Subsystem:
multimedia card (mmc), secure digital (sd) and sdio subsystem, the rest · Maintainers:
Ulf Hansson, Linus Torvalds
Introduce a new device tree flag to cap the maximum High-Speed (HS) mode frequency for SD cards, accommodating board-specific constraints such as the inclusion of a level shifter which cannot support the default 50Mhz HS frequency and others. Signed-off-by: Sarthak Garg <redacted> --- drivers/mmc/core/host.c | 2 ++ drivers/mmc/core/sd.c | 2 +- include/linux/mmc/host.h | 1 + 3 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index dacb5bd9bb71..3fe6ae56a6ae 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c@@ -302,6 +302,8 @@ int mmc_of_parse(struct mmc_host *host) /* f_max is obtained from the optional "max-frequency" property */ device_property_read_u32(dev, "max-frequency", &host->f_max); + device_property_read_u32(dev, "max-sd-hs-hz", &host->max_sd_hs_hz); + /* * Configure CD and WP pins. They are both by default active low to * match the SDHCI spec. If GPIOs are provided for CD and / or WP, the
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index ec02067f03c5..67cd63004829 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c@@ -359,7 +359,7 @@ static int mmc_read_switch(struct mmc_card *card) } if (status[13] & SD_MODE_HIGH_SPEED) - card->sw_caps.hs_max_dtr = HIGH_SPEED_MAX_DTR; + card->sw_caps.hs_max_dtr = card->host->max_sd_hs_hz ?: HIGH_SPEED_MAX_DTR; if (card->scr.sda_spec3) { card->sw_caps.sd3_bus_mode = status[13];
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 68f09a955a90..a698b4b02d95 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h@@ -565,6 +565,7 @@ struct mmc_host { int hsq_depth; u32 err_stats[MMC_ERR_MAX]; + unsigned int max_sd_hs_hz; unsigned long private[] ____cacheline_aligned; };
--
2.34.1