[PATCH v5 3/9] mmc: sdhci-of-k1: add regulator and pinctrl voltage switching support

Iker Pedrosa
2026-03-30T08:38:29Z

Add voltage switching infrastructure for UHS-I modes by integrating both
regulator framework (for supply voltage control) and pinctrl state
switching (for pin drive strength optimization).

- Add regulator supply parsing and voltage switching callback
- Add optional pinctrl state switching between "default" (3.3V) and
"state_uhs" (1.8V) configurations
- Enable coordinated voltage and pin configuration changes for UHS modes

This provides complete voltage switching support while maintaining
backward compatibility when pinctrl states are not defined.

Tested-by: Anand Moon <linux.amoon@gmail.com>
Tested-by: Trevor Gamblin <tgamblin@baylibre.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Iker Pedrosa <ikerpedrosam@gmail.com>
---
drivers/mmc/host/sdhci-of-k1.c | 72 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 72 insertions(+)

diff --git a/drivers/mmc/host/sdhci-of-k1.c b/drivers/mmc/host/sdhci-of-k1.c
index 0dd06fc19b8574ae1b00f7e5d09b7d4c87d06770..234e258af25996e7bbcd0b70366c7480bf62bee7 100644
--- a/drivers/mmc/host/sdhci-of-k1.c
+++ b/drivers/mmc/host/sdhci-of-k1.c
@@ -16,6 +16,7 @@
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/reset.h>
+#include <linux/pinctrl/consumer.h>
#include <linux/platform_device.h>

#include "sdhci.h"
@@ -71,6 +72,9 @@
struct spacemit_sdhci_host {
struct clk *clk_core;
struct clk *clk_io;
+ struct pinctrl *pinctrl;
+ struct pinctrl_state *pinctrl_default;
+ struct pinctrl_state *pinctrl_uhs;
};

/* All helper functions will update clr/set while preserve rest bits */
@@ -219,6 +223,46 @@ static void spacemit_sdhci_pre_hs400_to_hs200(struct mmc_host *mmc)
SPACEMIT_SDHC_PHY_CTRL_REG);
}

+static int spacemit_sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
+ struct mmc_ios *ios)
+{
+ struct sdhci_host *host = mmc_priv(mmc);
+ struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+ struct spacemit_sdhci_host *sdhst = sdhci_pltfm_priv(pltfm_host);
+ struct pinctrl_state *state;
+ int ret;
+
+ ret = sdhci_start_signal_voltage_switch(mmc, ios);
+ if (ret)
+ return ret;
+
+ if (!sdhst->pinctrl)
+ return 0;
+
+ /* Select appropriate pinctrl state based on signal voltage */
+ switch (ios->signal_voltage) {
+ case MMC_SIGNAL_VOLTAGE_330:
+ state = sdhst->pinctrl_default;
+ break;
+ case MMC_SIGNAL_VOLTAGE_180:
+ state = sdhst->pinctrl_uhs;
+ break;
+ default:
+ dev_warn(mmc_dev(mmc), "unsupported voltage %d\n", ios->signal_voltage);
+ return 0;
+ }
+
+ ret = pinctrl_select_state(sdhst->pinctrl, state);
+ if (ret) {
+ dev_warn(mmc_dev(mmc), "failed to select pinctrl state: %d\n", ret);
+ return 0;
+ }
+ dev_dbg(mmc_dev(mmc), "switched to %s pinctrl state\n",
+ ios->signal_voltage == MMC_SIGNAL_VOLTAGE_180 ? "UHS" : "default");
+
+ return 0;
+}
+
static inline int spacemit_sdhci_get_clocks(struct device *dev,
struct sdhci_pltfm_host *pltfm_host)
{
@@ -252,6 +296,30 @@ static inline int spacemit_sdhci_get_resets(struct device *dev)
return 0;
}

+static inline void spacemit_sdhci_get_pins(struct device *dev,
+ struct sdhci_pltfm_host *pltfm_host)
+{
+ struct spacemit_sdhci_host *sdhst = sdhci_pltfm_priv(pltfm_host);
+
+ sdhst->pinctrl = devm_pinctrl_get(dev);
+ if (IS_ERR(sdhst->pinctrl)) {
+ sdhst->pinctrl = NULL;
+ dev_dbg(dev, "pinctrl not available, voltage switching will work without it\n");
+ return;
+ }
+
+ sdhst->pinctrl_default = pinctrl_lookup_state(sdhst->pinctrl, "default");
+ if (IS_ERR(sdhst->pinctrl_default))
+ sdhst->pinctrl_default = NULL;
+
+ sdhst->pinctrl_uhs = pinctrl_lookup_state(sdhst->pinctrl, "state_uhs");
+ if (IS_ERR(sdhst->pinctrl_uhs))
+ sdhst->pinctrl_uhs = NULL;
+
+ dev_dbg(dev, "pinctrl setup: default=%p, uhs=%p\n",
+ sdhst->pinctrl_default, sdhst->pinctrl_uhs);
+}
+
static const struct sdhci_ops spacemit_sdhci_ops = {
.get_max_clock = spacemit_sdhci_clk_get_max_clock,
.reset = spacemit_sdhci_reset,
@@ -324,6 +392,10 @@ static int spacemit_sdhci_probe(struct platform_device *pdev)

host->mmc->caps |= MMC_CAP_NEED_RSP_BUSY;

+ spacemit_sdhci_get_pins(dev, pltfm_host);
+
+ host->mmc_host_ops.start_signal_voltage_switch = spacemit_sdhci_start_signal_voltage_switch;
+
ret = spacemit_sdhci_get_clocks(dev, pltfm_host);
if (ret)
goto err_pltfm;

--
2.53.0