mmc: tegra: allow disabling external clock loopback
Introduce CONFIG_TEGRA124_MMC_DISABLE_EXT_LOOPBACK to disable the external clock
loopback and use the internal one on SDMMC3 as per the SDMMC_VENDOR_MISC_CNTRL_0
register's SDMMC_SPARE1 bits being set to 0xfffd according to the TRM.
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Marcel Ziswiler <marcel@ziswiler.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/drivers/mmc/tegra_mmc.c b/drivers/mmc/tegra_mmc.c
index 0df74ef..6c6affb 100644
--- a/drivers/mmc/tegra_mmc.c
+++ b/drivers/mmc/tegra_mmc.c
@@ -513,6 +513,22 @@
tegra_mmc_reset(priv, mmc);
+#if defined(CONFIG_TEGRA124_MMC_DISABLE_EXT_LOOPBACK)
+ /*
+ * Disable the external clock loopback and use the internal one on
+ * SDMMC3 as per the SDMMC_VENDOR_MISC_CNTRL_0 register's SDMMC_SPARE1
+ * bits being set to 0xfffd according to the TRM.
+ *
+ * TODO(marcel.ziswiler@toradex.com): Move to device tree controlled
+ * approach once proper kernel integration made it mainline.
+ */
+ if (priv->reg == (void *)0x700b0400) {
+ mask = readl(&priv->reg->venmiscctl);
+ mask &= ~TEGRA_MMC_MISCON_ENABLE_EXT_LOOPBACK;
+ writel(mask, &priv->reg->venmiscctl);
+ }
+#endif
+
priv->version = readw(&priv->reg->hcver);
debug("host version = %x\n", priv->version);