[PATCH v9 2/8] mmc: sdhci-of-k1: enable essential clock infrastructure for SD operation

From: Iker Pedrosa <ikerpedrosam@gmail.com>
To: Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	 Conor Dooley <conor+dt@kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	 Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	 Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>,  Yixun Lan <dlan@kernel.org>,
	Ulf Hansson <ulfh@kernel.org>,  Ulf Hansson <ulfh@kernel.org>,
	Yixun Lan <dlan@kernel.org>
Cc: Trevor Gamblin <tgamblin@baylibre.com>,
	devicetree@vger.kernel.org,
	Michael Opdenacker <michael.opdenacker@rootcommit.com>,
	Troy Mitchell <troy.mitchell@linux.dev>,
	linux-mmc@vger.kernel.org,
	Javier Martinez Canillas <javierm@redhat.com>,
	linux-kernel@vger.kernel.org, Vincent Legoll <legoll@online.fr>,
	linux-riscv@lists.infradead.org, spacemit@lists.linux.dev,
	Iker Pedrosa <ikerpedrosam@gmail.com>
Subject: [PATCH v9 2/8] mmc: sdhci-of-k1: enable essential clock infrastructure for SD operation
Date: Mon, 11 May 2026 10:53:57 +0200	[thread overview]
Message-ID: <20260511-orangepi-sd-card-uhs-v9-2-ae48c0b2b2cf@gmail.com> (raw)
In-Reply-To: <20260511-orangepi-sd-card-uhs-v9-0-ae48c0b2b2cf@gmail.com>

Ensure SD card pins receive clock signals by enabling pad clock
generation and overriding automatic clock gating. Required for all SD
operation modes.

The SDHC_GEN_PAD_CLK_ON setting in LEGACY_CTRL_REG is safe for both SD
and eMMC operation as both protocols use the same physical MMC interface
pins and require proper clock signal generation at the hardware level
for signal integrity and timing.

Additional SD-specific clock overrides (SDHC_OVRRD_CLK_OEN and
SDHC_FORCE_CLK_ON) are conditionally applied only for SD-only
controllers to handle removable card scenarios.

Tested-by: Anand Moon <linux.amoon@gmail.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Trevor Gamblin <tgamblin@baylibre.com>
Reviewed-by: Troy Mitchell <troy.mitchell@linux.dev>
Tested-by: Vincent Legoll <legoll@online.fr>
Signed-off-by: Iker Pedrosa <ikerpedrosam@gmail.com>
---
 drivers/mmc/host/sdhci-of-k1.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/mmc/host/sdhci-of-k1.c b/drivers/mmc/host/sdhci-of-k1.c
index 455656f9842d..0dd06fc19b85 100644
--- a/drivers/mmc/host/sdhci-of-k1.c
+++ b/drivers/mmc/host/sdhci-of-k1.c
@@ -21,6 +21,13 @@
 #include "sdhci.h"
 #include "sdhci-pltfm.h"
 
+#define SPACEMIT_SDHC_OP_EXT_REG	0x108
+#define  SDHC_OVRRD_CLK_OEN		BIT(11)
+#define  SDHC_FORCE_CLK_ON		BIT(12)
+
+#define SPACEMIT_SDHC_LEGACY_CTRL_REG	0x10C
+#define  SDHC_GEN_PAD_CLK_ON		BIT(6)
+
 #define SPACEMIT_SDHC_MMC_CTRL_REG	0x114
 #define  SDHC_MISC_INT_EN		BIT(1)
 #define  SDHC_MISC_INT			BIT(2)
@@ -101,6 +108,12 @@ static void spacemit_sdhci_reset(struct sdhci_host *host, u8 mask)
 
 	if (!(host->mmc->caps2 & MMC_CAP2_NO_MMC))
 		spacemit_sdhci_setbits(host, SDHC_MMC_CARD_MODE, SPACEMIT_SDHC_MMC_CTRL_REG);
+
+	spacemit_sdhci_setbits(host, SDHC_GEN_PAD_CLK_ON, SPACEMIT_SDHC_LEGACY_CTRL_REG);
+
+	if (host->mmc->caps2 & MMC_CAP2_NO_MMC)
+		spacemit_sdhci_setbits(host, SDHC_OVRRD_CLK_OEN | SDHC_FORCE_CLK_ON,
+				       SPACEMIT_SDHC_OP_EXT_REG);
 }
 
 static void spacemit_sdhci_set_uhs_signaling(struct sdhci_host *host, unsigned int timing)

-- 
2.54.0


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