linux-kernel - [PATCH V3 3/4] mmc: core: Introduce a new flag max-sd-hs-frequency

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Message-Id: <20250618072818.1667097-4-quic_sartgarg@quicinc.com>
Date: Wed, 18 Jun 2025 12:58:17 +0530
From: Sarthak Garg <quic_sartgarg@...cinc.com>
To: Ulf Hansson <ulf.hansson@...aro.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>
Cc: linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        quic_cang@...cinc.com, quic_nguyenb@...cinc.com,
        quic_rampraka@...cinc.com, quic_pragalla@...cinc.com,
        quic_sayalil@...cinc.com, quic_nitirawa@...cinc.com,
        quic_bhaskarv@...cinc.com, kernel@....qualcomm.com,
        Sarthak Garg <quic_sartgarg@...cinc.com>
Subject: [PATCH V3 3/4] mmc: core: Introduce a new flag max-sd-hs-frequency

Introduce a new device tree flag to cap the maximum High-Speed (HS)
mode frequency for SD cards, accommodating vendor-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 <quic_sartgarg@...cinc.com>
---
 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..7892e80bc073 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-frequency", &host->max_sd_hs_freq);
+
 	/*
 	 * 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..d2f1766bddb4 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_freq ?: 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..552e8a22c0a2 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_freq;
 	unsigned long		private[] ____cacheline_aligned;
 };
 
-- 
2.34.1