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

Chris Zhong
2017-02-15T03:38:45Z

Hi John

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.

[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__);