linux-kernel - Re: [PATCH v4 23/23] drm/rockchip: dw-mipi-dsi: add reset control

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Date:   Thu, 2 Mar 2017 13:56:46 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     John Keeping <john@...anate.com>
Cc:     Mark Yao <mark.yao@...k-chips.com>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        linux-rockchip@...ts.infradead.org,
        Sean Paul <seanpaul@...omium.org>,
        Chris Zhong <zyw@...k-chips.com>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v4 23/23] drm/rockchip: dw-mipi-dsi: add reset control

+ devicetree

Hi,

On Fri, Feb 24, 2017 at 12:55:06PM +0000, John Keeping wrote:
> In order to fully reset the state of the MIPI controller we must assert
> this reset.
> 
> This is slightly more complicated than it could be in order to maintain
> compatibility with device trees that do not specify the reset property.
> 
> Signed-off-by: John Keeping <john@...anate.com>
> Reviewed-by: Chris Zhong <zyw@...k-chips.com>
> ---
> v4:
> - Fix error check for devm_reset_control_get() to use ENOENT
> v3:
> - Add Chris' Reviewed-by
> Unchanged in v2
> ---
>  drivers/gpu/drm/rockchip/dw-mipi-dsi.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> index 0c4bae711e84..30da75667334 100644
> --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> @@ -13,6 +13,7 @@
>  #include <linux/module.h>
>  #include <linux/of_device.h>
>  #include <linux/regmap.h>
> +#include <linux/reset.h>
>  #include <linux/mfd/syscon.h>
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_crtc.h>
> @@ -1144,6 +1145,7 @@ static int dw_mipi_dsi_bind(struct device *dev, struct device *master,
>  			of_match_device(dw_mipi_dsi_dt_ids, dev);
>  	const struct dw_mipi_dsi_plat_data *pdata = of_id->data;
>  	struct platform_device *pdev = to_platform_device(dev);
> +	struct reset_control *apb_rst;
>  	struct drm_device *drm = data;
>  	struct dw_mipi_dsi *dsi;
>  	struct resource *res;
> @@ -1182,6 +1184,35 @@ static int dw_mipi_dsi_bind(struct device *dev, struct device *master,
>  		return ret;
>  	}
>  
> +	/*
> +	 * Note that the reset was not defined in the initial device tree, so
> +	 * we have to be prepared for it not being found.
> +	 */
> +	apb_rst = devm_reset_control_get(dev, "apb");

Did this reset ever get documented in the device tree bindings? I
couldn't find it. Perhaps a follow-up patch is in order?

[...]

Brian