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

John Keeping
2017-02-16T14:11:25Z

On Thu, 16 Feb 2017 10:12:33 +0800, Chris Zhong wrote:

> 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@metanate.com>
> >>> Reviewed-by: Chris Zhong <zyw@rock-chips.com>
> >>> ---
> >>> 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@free.fr>
> >> 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@free.fr>
> >> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> >>
> >>
> >>> + 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.

Good point, I'll fix this.

John