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

From: Chris Zhong
Date: Tue Feb 14 2017 - 22:39:13 EST


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@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.

[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);
+ 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__);