Commit 05193dc38197 ("drm/bridge: Make the bridge chain a double-linked
list") patched the bridge chain logic to use a double-linked list instead
of a single-linked list. This change induced changes to the Exynos driver
which was manually resetting the encoder->bridge element to NULL to
control the enable/disable sequence of the bridge chain. During this
conversion, 2 bugs were introduced:
1/ list_splice() was used to move chain elements to our own internal
chain, but list_splice() does not reset the source list to an empty
state, leading to unexpected bridge hook calls when
drm_bridge_chain_xxx() helpers were called by the core. Replacing
the list_splice() call by list_splice_init() fixes this problem.
2/ drm_bridge_chain_xxx() helpers operate on the
bridge->encoder->bridge_chain list, which is now empty. When the
helper uses list_for_each_entry_reverse() we end up with no operation
done which is not what we want. But that's even worse when the helper
uses list_for_each_entry_from(), because in that case we end up in
an infinite loop searching for the list head element which is no
longer encoder->bridge_chain but exynos_dsi->bridge_chain. To address
that problem we stop using the bridge chain helpers and call the
hooks directly.
Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Fixes: 05193dc38197 ("drm/bridge: Make the bridge chain a double-linked list")
Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
---
Hello Marek,
I'm perfectly fine applying your patch instead of this one if you prefer
to restrict the logic to a single bridge per chain. I just sent this
patch in case your okay with the slightly different version I propose
here.
Let me know what you want to do.
Regards,
Boris
---
drivers/gpu/drm/exynos/exynos_drm_dsi.c | 29 ++++++++++++++++++++-----
1 file changed, 24 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/exynos/exynos_drm_dsi.c b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
index 3955f84dc893..33628d85edad 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dsi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
@@ -1378,6 +1378,7 @@ static void exynos_dsi_unregister_te_irq(struct exynos_dsi *dsi)
static void exynos_dsi_enable(struct drm_encoder *encoder)
{
struct exynos_dsi *dsi = encoder_to_dsi(encoder);
+ struct drm_bridge *iter;
int ret;
if (dsi->state & DSIM_STATE_ENABLED)
@@ -1391,7 +1392,11 @@ static void exynos_dsi_enable(struct drm_encoder *encoder)
if (ret < 0)
goto err_put_sync;
} else {
- drm_bridge_chain_pre_enable(dsi->out_bridge);
+ list_for_each_entry_reverse(iter, &dsi->bridge_chain,
+ chain_node) {
+ if (iter->funcs->pre_enable)
+ iter->funcs->pre_enable(iter);
+ }
}
exynos_dsi_set_display_mode(dsi);
@@ -1402,7 +1407,10 @@ static void exynos_dsi_enable(struct drm_encoder *encoder)
if (ret < 0)
goto err_display_disable;
} else {
- drm_bridge_chain_enable(dsi->out_bridge);
+ list_for_each_entry(iter, &dsi->bridge_chain, chain_node) {
+ if (iter->funcs->enable)
+ iter->funcs->enable(iter);
+ }
}
dsi->state |= DSIM_STATE_VIDOUT_AVAILABLE;
@@ -1420,6 +1428,7 @@ static void exynos_dsi_enable(struct drm_encoder *encoder)
static void exynos_dsi_disable(struct drm_encoder *encoder)
{
struct exynos_dsi *dsi = encoder_to_dsi(encoder);
+ struct drm_bridge *iter;
if (!(dsi->state & DSIM_STATE_ENABLED))
return;
@@ -1427,10 +1436,20 @@ static void exynos_dsi_disable(struct drm_encoder *encoder)
dsi->state &= ~DSIM_STATE_VIDOUT_AVAILABLE;
drm_panel_disable(dsi->panel);
- drm_bridge_chain_disable(dsi->out_bridge);
+
+ list_for_each_entry_reverse(iter, &dsi->bridge_chain, chain_node) {
+ if (iter->funcs->disable)
+ iter->funcs->disable(iter);
+ }
+
exynos_dsi_set_display_enable(dsi, false);
drm_panel_unprepare(dsi->panel);
- drm_bridge_chain_post_disable(dsi->out_bridge);
+
+ list_for_each_entry(iter, &dsi->bridge_chain, chain_node) {
+ if (iter->funcs->post_disable)
+ iter->funcs->post_disable(iter);
+ }
+
dsi->state &= ~DSIM_STATE_ENABLED;
pm_runtime_put_sync(dsi->dev);
}
@@ -1523,7 +1542,7 @@ static int exynos_dsi_host_attach(struct mipi_dsi_host *host,
if (out_bridge) {
drm_bridge_attach(encoder, out_bridge, NULL);
dsi->out_bridge = out_bridge;
- list_splice(&encoder->bridge_chain, &dsi->bridge_chain);
+ list_splice_init(&encoder->bridge_chain, &dsi->bridge_chain);
} else {
int ret = exynos_dsi_create_connector(encoder);
--
2.23.0
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