[PATCH RESEND v3 2/3] mmc: sdhci_am654: Add sdhci_am654_start_signal_voltage_switch

Judith Mendez
2025-04-22T22:05:29Z

The sdhci_start_signal_voltage_switch function sets
V1P8_SIGNAL_ENA by default after switching to 1v8 signaling.
V1P8_SIGNAL_ENA has a timing component where it determines
whether to launch cmd/data on neg edge (half cycle timing)
or pos edge (full cycle timing) of clock. V1P8_SIGNAL_ENA also
has a voltage switch component where if there exists an internal
LDO, for SD this bit is used to switch from 3.3V to 1.8V IO
signal voltage.

The sequence is to switch to 1.8 IO voltage, set V1P8_SIGNAL_ENA,
change bus width, then update HIGH_SPEED_ENA & UHS_MODE_SELECT.
During bus width change is when eMMC failures are seen with
Kingston eMMC and various types SD cards across Sitara K3 SoCs.

So, add a quirk to suppress V1P8_SIGNAL_ENA and do not enable by
default for eMMC since it is anyways optional for this interface
and parse DT property: ti,fails-without-test-cd to apply the quirk
for SD cards.

Signed-off-by: Judith Mendez <jm@ti.com>
Suggested-by: Hiago De Franco <hiago.franco@toradex.com>
Fixes: ac5a41b472b4 ("Revert "mmc: sdhci_am654: Add sdhci_am654_start_signal_voltage_switch"")
Fixes: 941a7abd4666 ("mmc: sdhci_am654: Add sdhci_am654_start_signal_voltage_switch")
Cc: stable@vger.kernel.org
---
drivers/mmc/host/sdhci_am654.c | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)

diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
index f75c31815ab0..d4cafc7af97d 100644
--- a/drivers/mmc/host/sdhci_am654.c
+++ b/drivers/mmc/host/sdhci_am654.c
@@ -87,6 +87,7 @@
#define CLOCK_TOO_SLOW_HZ 50000000
#define SDHCI_AM654_AUTOSUSPEND_DELAY -1
#define RETRY_TUNING_MAX 10
+#define BUS_WIDTH_8 8

/* Command Queue Host Controller Interface Base address */
#define SDHCI_AM654_CQE_BASE_ADDR 0x200
@@ -155,6 +156,7 @@ struct sdhci_am654_data {
u32 tuning_loop;

#define SDHCI_AM654_QUIRK_FORCE_CDTEST BIT(0)
+#define SDHCI_AM654_QUIRK_SUPPRESS_V1P8_ENA BIT(1)
};

struct window {
@@ -356,6 +358,29 @@ static void sdhci_j721e_4bit_set_clock(struct sdhci_host *host,
sdhci_set_clock(host, clock);
}

+static int sdhci_am654_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 sdhci_am654_data *sdhci_am654 = sdhci_pltfm_priv(pltfm_host);
+ int ret;
+
+ if ((sdhci_am654->quirks & SDHCI_AM654_QUIRK_SUPPRESS_V1P8_ENA) &&
+ ios->signal_voltage == MMC_SIGNAL_VOLTAGE_180) {
+ if (!IS_ERR(mmc->supply.vqmmc)) {
+ ret = mmc_regulator_set_vqmmc(mmc, ios);
+ if (ret < 0) {
+ pr_err("%s: Switching to 1.8V signalling voltage failed,\n",
+ mmc_hostname(mmc));
+ return -EIO;
+ }
+ }
+ return 0;
+ }
+
+ return sdhci_start_signal_voltage_switch(mmc, ios);
+}
+
static u8 sdhci_am654_write_power_on(struct sdhci_host *host, u8 val, int reg)
{
writeb(val, host->ioaddr + reg);
@@ -802,6 +827,7 @@ static int sdhci_am654_get_of_property(struct platform_device *pdev,
{
struct device *dev = &pdev->dev;
int drv_strength;
+ u32 bus_width;
int ret;

if (sdhci_am654->flags & DLL_PRESENT) {
@@ -844,6 +870,11 @@ static int sdhci_am654_get_of_property(struct platform_device *pdev,
if (device_property_read_bool(dev, "ti,fails-without-test-cd"))
sdhci_am654->quirks |= SDHCI_AM654_QUIRK_FORCE_CDTEST;

+ /* Suppress V1P8_SIGNAL_ENA */
+ device_property_read_u32(dev, "bus-width", &bus_width);
+ if (bus_width == BUS_WIDTH_8 || device_property_read_bool(dev, "ti,suppress-v1p8-ena"))
+ sdhci_am654->quirks |= SDHCI_AM654_QUIRK_SUPPRESS_V1P8_ENA;
+
sdhci_get_of_property(pdev);

return 0;
@@ -940,6 +971,7 @@ static int sdhci_am654_probe(struct platform_device *pdev)
goto err_pltfm_free;
}

+ host->mmc_host_ops.start_signal_voltage_switch = sdhci_am654_start_signal_voltage_switch;
host->mmc_host_ops.execute_tuning = sdhci_am654_execute_tuning;

pm_runtime_get_noresume(dev);
--
2.49.0