mmc: dw_mmc: add reset support to dwmmc host controller

Dwmmc host controller may in unknown state when entering kernel boot. One
example is when booting from eMMC, bootloader need initialize MMC host
controller into some state so it can read. In order to make sure MMC host
controller in a clean initial state, this reset support is added.

With this patch, a 'resets' property can be added into dw_mmc device
tree node. The hardware logic is: dwmmc host controller IP receives a reset
signal from a 'reset provider' (eg. power management unit). The 'resets'
property points to this reset signal. So, during dwmmc driver probe,
it can use this signal to reset itself.

Refer to [1] for more information.

[1] Documentation/devicetree/bindings/reset/reset.txt

Signed-off-by: Guodong Xu <guodong.xu@linaro.org>
Signed-off-by: Xinwei Kong <kong.kongxinwei@hisilicon.com>
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 1a1e1e1ac7c143fec53721cb01a8f73b059a8285..e7eef75a65ef0917a965acb00f13e7089e40091b 100644 (file)
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -2876,6 +2876,13 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
        if (!pdata)
                return ERR_PTR(-ENOMEM);
 
+       /* find reset controller when exist */
+       pdata->rstc = devm_reset_control_get_optional(dev, NULL);
+       if (IS_ERR(pdata->rstc)) {
+               if (PTR_ERR(pdata->rstc) == -EPROBE_DEFER)
+                       return ERR_PTR(-EPROBE_DEFER);
+       }
+
        /* find out number of slots supported */
        of_property_read_u32(np, "num-slots", &pdata->num_slots);
 
@@ -2947,7 +2954,9 @@ int dw_mci_probe(struct dw_mci *host)
 
        if (!host->pdata) {
                host->pdata = dw_mci_parse_dt(host);
-               if (IS_ERR(host->pdata)) {
+               if (PTR_ERR(host->pdata) == -EPROBE_DEFER) {
+                       return -EPROBE_DEFER;
+               } else if (IS_ERR(host->pdata)) {
                        dev_err(host->dev, "platform data not available\n");
                        return -EINVAL;
                }
@@ -3001,6 +3010,12 @@ int dw_mci_probe(struct dw_mci *host)
                }
        }
 
+       if (!IS_ERR(host->pdata->rstc)) {
+               reset_control_assert(host->pdata->rstc);
+               usleep_range(10, 50);
+               reset_control_deassert(host->pdata->rstc);
+       }
+
        setup_timer(&host->cmd11_timer,
                    dw_mci_cmd11_timer, (unsigned long)host);
 
@@ -3150,6 +3165,9 @@ err_dmaunmap:
        if (host->use_dma && host->dma_ops->exit)
                host->dma_ops->exit(host);
 
+       if (!IS_ERR(host->pdata->rstc))
+               reset_control_assert(host->pdata->rstc);
+
 err_clk_ciu:
        clk_disable_unprepare(host->ciu_clk);
 
@@ -3180,6 +3198,9 @@ void dw_mci_remove(struct dw_mci *host)
        if (host->use_dma && host->dma_ops->exit)
                host->dma_ops->exit(host);
 
+       if (!IS_ERR(host->pdata->rstc))
+               reset_control_assert(host->pdata->rstc);
+
        clk_disable_unprepare(host->ciu_clk);
        clk_disable_unprepare(host->biu_clk);
 }

diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
index 83b0edfce471c2a9ab536a5ae616e070ac34fc9e..f5af2bd35e7fdffbab622c121db2433e980f23e0 100644 (file)
--- a/include/linux/mmc/dw_mmc.h
+++ b/include/linux/mmc/dw_mmc.h
@@ -17,6 +17,7 @@
 #include <linux/scatterlist.h>
 #include <linux/mmc/core.h>
 #include <linux/dmaengine.h>
+#include <linux/reset.h>
 
 #define MAX_MCI_SLOTS  2
 
@@ -259,6 +260,7 @@ struct dw_mci_board {
        /* delay in mS before detecting cards after interrupt */
        u32 detect_delay_ms;
 
+       struct reset_control *rstc;
        struct dw_mci_dma_ops *dma_ops;
        struct dma_pdata *data;
 };