[PATCH RFC 4/4] mmc: sdhci-of-dwcmshc: Add support for T-Head TH1520

[Drew Fustini <dfustini@baylibre.com>]

Add basic support for the T-Head TH1520 SoC mmc controller. The new
compatible "thead,th1520-dwcmshc" enables basic support by:

 - Enabling v4 mode to properly communicate with the mmc device
 - Setting quirk to disable ADMA
 - Setting flag to disable SDMA and force PIO mode
 - Turing .reset op into a no-op as the driver does not yet know how to
   configure the phy. Rely on the vendor u-boot to have configured the
   phy and do not reset the controller in Linux.

Signed-off-by: Drew Fustini <dfustini@baylibre.com>
---
 drivers/mmc/host/sdhci-of-dwcmshc.c | 42 +++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
index e68cd87998c8..8573aff25a81 100644
--- a/drivers/mmc/host/sdhci-of-dwcmshc.c
+++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
@@ -337,6 +337,14 @@ static void rk35xx_sdhci_reset(struct sdhci_host *host, u8 mask)
 	sdhci_reset(host, mask);
 }
 
+static void th1520_sdhci_reset(struct sdhci_host *host, u8 mask)
+{
+	/*
+	 * MMC controller and phy is configured by vendor u-boot so
+	 * take the simplistic approach of not doing reset in Linux.
+	 */
+}
+
 static const struct sdhci_ops sdhci_dwcmshc_ops = {
 	.set_clock		= sdhci_set_clock,
 	.set_bus_width		= sdhci_set_bus_width,
@@ -355,6 +363,15 @@ static const struct sdhci_ops sdhci_dwcmshc_rk35xx_ops = {
 	.adma_write_desc	= dwcmshc_adma_write_desc,
 };
 
+static const struct sdhci_ops sdhci_dwcmshc_th1520_ops = {
+	.set_clock		= sdhci_set_clock,
+	.set_bus_width		= sdhci_set_bus_width,
+	.set_uhs_signaling	= dwcmshc_set_uhs_signaling,
+	.get_max_clock		= dwcmshc_get_max_clock,
+	.reset			= th1520_sdhci_reset,
+	.adma_write_desc	= dwcmshc_adma_write_desc,
+};
+
 static const struct sdhci_pltfm_data sdhci_dwcmshc_pdata = {
 	.ops = &sdhci_dwcmshc_ops,
 	.quirks = SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN,
@@ -378,6 +395,13 @@ static const struct sdhci_pltfm_data sdhci_dwcmshc_rk35xx_pdata = {
 		   SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN,
 };
 
+static const struct sdhci_pltfm_data sdhci_dwcmshc_th1520_pdata = {
+	.ops = &sdhci_dwcmshc_th1520_ops,
+	.quirks = SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN | SDHCI_QUIRK_BROKEN_DMA |
+		  SDHCI_QUIRK_BROKEN_ADMA,
+	.quirks2 = SDHCI_QUIRK2_PRESET_VALUE_BROKEN,
+};
+
 static int dwcmshc_rk35xx_init(struct sdhci_host *host, struct dwcmshc_priv *dwc_priv)
 {
 	int err;
@@ -434,6 +458,10 @@ static void dwcmshc_rk35xx_postinit(struct sdhci_host *host, struct dwcmshc_priv
 }
 
 static const struct of_device_id sdhci_dwcmshc_dt_ids[] = {
+	{
+		.compatible = "thead,th1520-dwcmshc",
+		.data = &sdhci_dwcmshc_th1520_pdata,
+	},
 	{
 		.compatible = "rockchip,rk3588-dwcmshc",
 		.data = &sdhci_dwcmshc_rk35xx_pdata,
@@ -546,6 +574,20 @@ static int dwcmshc_probe(struct platform_device *pdev)
 		sdhci_enable_v4_mode(host);
 #endif
 
+	if (pltfm_data == &sdhci_dwcmshc_th1520_pdata) {
+		/*
+		 * The controller needs v4 mode enabled to properly
+		 * communicate with the mmc device.
+		 */
+		sdhci_enable_v4_mode(host);
+
+		/*
+		 * Set flag so the SDHCI host core will disable DMA
+		 * and use PIO mode.
+		 */
+		host->flags &= ~SDHCI_USE_SDMA;
+	}
+
 	host->mmc->caps |= MMC_CAP_WAIT_WHILE_BUSY;
 
 	err = sdhci_setup_host(host);

-- 
2.34.1