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

John Keeping
2017-02-15T12:39:44Z

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);
> > + 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__);