[v2,3/3] mmc: mediatek: add optional module reset property

[Wenbin Mei]

This patch fixs eMMC-Access on mt7622/Bpi-64.
Before we got these Errors on mounting eMMC ion R64:
[   48.664925] blk_update_request: I/O error, dev mmcblk0, sector 204800 op 0x1:(WRITE)
flags 0x800 phys_seg 1 prio class 0
[   48.676019] Buffer I/O error on dev mmcblk0p1, logical block 0, lost sync page write

This patch adds a optional reset management for msdc.
Sometimes the bootloader does not bring msdc register
to default state, so need reset the msdc controller.

Fixes: 966580ad236e ("mmc: mediatek: add support for MT7622 SoC")
Signed-off-by: Wenbin Mei <wenbin.mei@xxxxxxxxxxxx>
Tested-by: Frank Wunderlich <frank-w@xxxxxxxxxxxxxxx>
---
 drivers/mmc/host/mtk-sd.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
index 39e7fc54c438..2b243c03c9b2 100644
--- a/drivers/mmc/host/mtk-sd.c
+++ b/drivers/mmc/host/mtk-sd.c
@@ -22,6 +22,7 @@
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/interrupt.h>
+#include <linux/reset.h>
 
 #include <linux/mmc/card.h>
 #include <linux/mmc/core.h>
@@ -434,6 +435,7 @@ struct msdc_host {
 	struct msdc_save_para save_para; /* used when gate HCLK */
 	struct msdc_tune_para def_tune_para; /* default tune setting */
 	struct msdc_tune_para saved_tune_para; /* tune result of CMD21/CMD19 */
+	struct reset_control *reset;
 };
 
 static const struct mtk_mmc_compatible mt8135_compat = {
@@ -1516,6 +1518,12 @@ static void msdc_init_hw(struct msdc_host *host)
 	u32 val;
 	u32 tune_reg = host->dev_comp->pad_tune_reg;
 
+	if (!IS_ERR(host->reset)) {
+		reset_control_assert(host->reset);
+		usleep_range(10, 50);
+		reset_control_deassert(host->reset);
+	}
+
 	/* Configure to MMC/SD mode, clock free running */
 	sdr_set_bits(host->base + MSDC_CFG, MSDC_CFG_MODE | MSDC_CFG_CKPDN);
 
@@ -2273,6 +2281,11 @@ static int msdc_drv_probe(struct platform_device *pdev)
 	if (IS_ERR(host->src_clk_cg))
 		host->src_clk_cg = NULL;
 
+	host->reset = devm_reset_control_get_optional_exclusive(&pdev->dev,
+								"hrst");
+	if (PTR_ERR(host->reset) == -EPROBE_DEFER)
+		return PTR_ERR(host->reset);
+
 	host->irq = platform_get_irq(pdev, 0);
 	if (host->irq < 0) {
 		ret = -EINVAL;
-- 
2.18.0