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

[Wenbin Mei]

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.

Signed-off-by: Wenbin Mei <wenbin....@mediatek.com>
---
 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