From: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
The processor manual prescribes to clear reset of LVDS interface in CPG/MSSR
module before display on, and to assert the same reset line at display off
time, to have the module resuming in a known state.
The module is said to be in "standby state" at initialization time, and this
requires, according to section 37.3.7 of the manual, to de-assert the reset to
have it functional.
Based on the original patch from
Koji Matsuoka <koji.matsuoka.xm@xxxxxxxxxxx>
Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
Signed-off-by: Ulrich Hecht <uli+renesas@xxxxxxxx>
---
drivers/gpu/drm/rcar-du/rcar_lvds.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
index cd55576..f6a4f9c 100644
--- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
+++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
@@ -14,6 +14,7 @@
#include <linux/of_device.h>
#include <linux/of_graph.h>
#include <linux/platform_device.h>
+#include <linux/reset.h>
#include <linux/slab.h>
#include <drm/drm_atomic.h>
@@ -55,6 +56,7 @@ struct rcar_lvds {
void __iomem *mmio;
struct clk *clock;
+ struct reset_control *rst;
bool enabled;
struct drm_display_mode display_mode;
@@ -385,6 +387,12 @@ static void rcar_lvds_enable(struct drm_bridge *bridge)
if (ret < 0)
return;
+ ret = reset_control_deassert(lvds->rst);
+ if (ret < 0) {
+ clk_disable_unprepare(lvds->clock);
+ return;
+ }
+
/*
* Hardcode the channels and control signals routing for now.
*
@@ -476,6 +484,7 @@ static void rcar_lvds_disable(struct drm_bridge *bridge)
rcar_lvds_write(lvds, LVDCR1, 0);
rcar_lvds_write(lvds, LVDPLLCR, 0);
+ reset_control_assert(lvds->rst);
clk_disable_unprepare(lvds->clock);
lvds->enabled = false;
@@ -692,6 +701,12 @@ static int rcar_lvds_probe(struct platform_device *pdev)
return PTR_ERR(lvds->clock);
}
+ lvds->rst = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
+ if (IS_ERR(lvds->rst)) {
+ dev_err(&pdev->dev, "failed to get reset\n");
+ return PTR_ERR(lvds->rst);
+ }
+
drm_bridge_add(&lvds->bridge);
return 0;
--
2.7.4
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