linux-kernel - Re: [PATCH v4 2/2] mmc: dw_mmc: add reset support to dwmmc host controller

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Message-ID: <d39854ef-1a6a-bd58-2500-4db7f62f63c1@rock-chips.com>
Date:	Thu, 11 Aug 2016 10:23:37 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Guodong Xu <guodong.xu@...aro.org>, heiko@...ech.de,
	shawn.lin@...k-chips.com, jh80.chung@...sung.com,
	robh+dt@...nel.org, mark.rutland@....com, ulf.hansson@...aro.org
Cc:	shawn.lin@...k-chips.com, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mmc@...r.kernel.org,
	Xinwei Kong <kong.kongxinwei@...ilicon.com>,
	Zhangfei Gao <zhangfei.gao@...aro.org>
Subject: Re: [PATCH v4 2/2] mmc: dw_mmc: add reset support to dwmmc host
 controller

On 2016/8/10 16:03, Guodong Xu wrote:
> 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@...aro.org>
> Signed-off-by: Xinwei Kong <kong.kongxinwei@...ilicon.com>
> Signed-off-by: Zhangfei Gao <zhangfei.gao@...aro.org>

Looks good to me,

Reviewed-by: Shawn Lin <shawn.lin@...k-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 32380d5..481d441 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -2915,6 +2915,13 @@ 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);
>
> @@ -2986,7 +2993,9 @@ 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;
>  		}
> @@ -3040,6 +3049,12 @@ 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);
>
> @@ -3189,6 +3204,9 @@ 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:
>  	if (!IS_ERR(host->ciu_clk))
>  		clk_disable_unprepare(host->ciu_clk);
> @@ -3221,6 +3239,9 @@ 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);
> +
>  	if (!IS_ERR(host->ciu_clk))
>  		clk_disable_unprepare(host->ciu_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;
>  };
>


-- 
Best Regards
Shawn Lin