[PATCH v5 0/2] mmc: dw_mmc: host controller reset support

[PATCH v5 0/2] mmc: dw_mmc: host controller reset support

[Guodong Xu]

mmc host controller registers may in abnormal state if mmc is used in
bootloader, eg. to load kernel from eMMC. Some controllers cann't
clear their registers when clk is set. They use dedicated reset
logics to do this.

In this patch, a 'resets' property is added into dw_mmc dts
node. When driver does parse_dt and probe, it calls reset API to
triiger 'reset' of dwmmc host controller. When probe error or
remove, it calls reset API to assert it.

Chip vendor's actual reset logics is implemented in reset driver, not
in dw_mmc code.

Please also refer to Documentation/devicetree/bindings/reset/reset.txt

Changelog:
v5:
 * rebase onto https://github.com/jh80chung/dw-mmc
v4:
 * add reset_control_assert() and usleep() before calling _deassert().

Guodong Xu (2):
  Documentation: synopsys-dw-mshc: add binding for resets
  mmc: dw_mmc: add reset support to dwmmc host controller

 .../devicetree/bindings/mmc/synopsys-dw-mshc.txt   |  4 ++++
 drivers/mmc/host/dw_mmc.c                          | 23 +++++++++++++++++++++-
 include/linux/mmc/dw_mmc.h                         |  2 ++
 3 files changed, 28 insertions(+), 1 deletion(-)

-- 
1.9.1

[PATCH v5 1/2] Documentation: synopsys-dw-mshc: add binding for resets

[Guodong Xu]

Add resets property to synopsys-dw-mshc bindings. It is intended to
represent the hardware reset signal present internally in some host
controller IC designs.

See Documentation/devicetree/bindings/reset/reset.txt for details.

Signed-off-by: Guodong Xu <guodong.xu@linaro.org>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Rob Herring <robh@kernel.org>
---
 Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.txt
index 8636f5a..4e00e85 100644
--- a/Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.txt
+++ b/Documentation/devicetree/bindings/mmc/synopsys-dw-mshc.txt
@@ -39,6 +39,10 @@ Required Properties:
 
 Optional properties:
 
+* resets: phandle + reset specifier pair, intended to represent hardware
+  reset signal present internally in some host controller IC designs.
+  See Documentation/devicetree/bindings/reset/reset.txt for details.
+
 * clocks: from common clock binding: handle to biu and ciu clocks for the
   bus interface unit clock and the card interface unit clock.
 
-- 
1.9.1

[PATCH v5 2/2] mmc: dw_mmc: add reset support to dwmmc host controller

[Guodong Xu]

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>
---
 drivers/mmc/host/dw_mmc.c  | 23 ++++++++++++++++++++++-
 include/linux/mmc/dw_mmc.h |  2 ++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 1b719a6..4dff0ee 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -2872,6 +2872,13 @@ 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);
 
@@ -2943,7 +2950,9 @@ 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;
 		}
@@ -2997,6 +3006,12 @@ 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);
 
@@ -3146,6 +3161,9 @@ 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);
 
@@ -3176,6 +3194,9 @@ 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 83b0edfc..f5af2bd 100644
--- 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;
 };
-- 
1.9.1

Re: [PATCH v5 0/2] mmc: dw_mmc: host controller reset support

[Jaehoon Chung]

Hi Guodong,

On 08/12/2016 05:51 PM, Guodong Xu wrote:
> mmc host controller registers may in abnormal state if mmc is used in
> bootloader, eg. to load kernel from eMMC. Some controllers cann't
> clear their registers when clk is set. They use dedicated reset
> logics to do this.
> 
> In this patch, a 'resets' property is added into dw_mmc dts
> node. When driver does parse_dt and probe, it calls reset API to
> triiger 'reset' of dwmmc host controller. When probe error or
> remove, it calls reset API to assert it.
> 
> Chip vendor's actual reset logics is implemented in reset driver, not
> in dw_mmc code.
> 
> Please also refer to Documentation/devicetree/bindings/reset/reset.txt
> 
> Changelog:
> v5:
>  * rebase onto https://github.com/jh80chung/dw-mmc
> v4:
>  * add reset_control_assert() and usleep() before calling _deassert().
> 
> Guodong Xu (2):
>   Documentation: synopsys-dw-mshc: add binding for resets
>   mmc: dw_mmc: add reset support to dwmmc host controller

Applied on my dw-mmc tree. Thanks!

Best Regards,
Jaehoon Chung

> 
>  .../devicetree/bindings/mmc/synopsys-dw-mshc.txt   |  4 ++++
>  drivers/mmc/host/dw_mmc.c                          | 23 +++++++++++++++++++++-
>  include/linux/mmc/dw_mmc.h                         |  2 ++
>  3 files changed, 28 insertions(+), 1 deletion(-)
>