Re: [PATCH v3 23/24] drm/rockchip: dw-mipi-dsi: add reset control

[Chris Zhong]

Hi John

On 02/15/2017 08:39 PM, John Keeping wrote:
> On Wed, 15 Feb 2017 11:38:45 +0800, Chris Zhong wrote:
>
> > On 01/29/2017 09:24 PM, 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@xxxxxxxxxxxx>
> > > Reviewed-by: Chris Zhong <zyw@xxxxxxxxxxxxxx>
> > > ---
> > > v3:
> > > - Add Chris' Reviewed-by
> > > Unchanged in v2
> > >
> > >    drivers/gpu/drm/rockchip/dw-mipi-dsi.c | 30 ++++++++++++++++++++++++++++++
> > >    1 file changed, 30 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> > > index 58cb8ace2fe8..cf3ca6b0cbdb 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>
> > > @@ -1124,6 +1125,7 @@ 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;
> > > @@ -1162,6 +1164,34 @@ 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");
> > > +	if (IS_ERR(apb_rst)) {
> > > +		if (PTR_ERR(apb_rst) == -ENODEV) {
> > According to [0], I think it should be -ENOENT here.
> Nice catch, I'll fix this.
>
> > [0]
> > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=3d81216fde465e76c5eae98f61d3666163634395
> >
> > commit 3d81216fde465e76c5eae98f61d3666163634395
> > Author: Alban Bedel <albeu@xxxxxxx>
> > Date:   Tue Sep 1 17:28:31 2015 +0200
> >
> >       reset: Fix of_reset_control_get() for consistent return values
> >
> >       When of_reset_control_get() is called without connection ID it returns
> >       -ENOENT when the 'resets' property doesn't exists or is an empty entry.
> >       However when a connection ID is given it returns -EINVAL when the
> > 'resets'
> >       property doesn't exists or the requested name can't be found. This is
> >       because the error code returned by of_property_match_string() is just
> >       passed down as an index to of_parse_phandle_with_args(), which then
> >       returns -EINVAL.
> >
> >       To get a consistent return value with both code paths we must return
> >       -ENOENT when of_property_match_string() fails.
> >
> >       Signed-off-by: Alban Bedel <albeu@xxxxxxx>
> >       Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> >
> >
> > > +			apb_rst = NULL;
> > > +		} else {
> > > +			dev_err(dev, "Unable to get reset control: %d\n", ret);
Also, we can not get error number from "ret" here.

> > > +			return PTR_ERR(apb_rst);
> > > +		}
> > > +	}
> > > +
> > > +	if (apb_rst) {
> > > +		ret = clk_prepare_enable(dsi->pclk);
> > > +		if (ret) {
> > > +			dev_err(dev, "%s: Failed to enable pclk\n", __func__);
> > > +			return ret;
> > > +		}
> > > +
> > > +		reset_control_assert(apb_rst);
> > > +		usleep_range(10, 20);
> > > +		reset_control_deassert(apb_rst);
> > > +
> > > +		clk_disable_unprepare(dsi->pclk);
> > > +	}
> > > +
> > >    	ret = clk_prepare_enable(dsi->pllref_clk);
> > >    	if (ret) {
> > >    		dev_err(dev, "%s: Failed to enable pllref_clk\n", __func__);