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 VC4 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
those list_splice() calls by list_splice_init() ones 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 vc4_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>
Cc: Eric Anholt <eric@xxxxxxxxxx>
Fixes: 05193dc38197 ("drm/bridge: Make the bridge chain a double-linked list")
Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
---
drivers/gpu/drm/vc4/vc4_dsi.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
index 6c5b80ad6154..fd8a2eb60505 100644
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -753,10 +753,19 @@ static void vc4_dsi_encoder_disable(struct drm_encoder *encoder)
struct vc4_dsi_encoder *vc4_encoder = to_vc4_dsi_encoder(encoder);
struct vc4_dsi *dsi = vc4_encoder->dsi;
struct device *dev = &dsi->pdev->dev;
+ struct drm_bridge *iter;
+
+ list_for_each_entry_reverse(iter, &dsi->bridge_chain, chain_node) {
+ if (iter->funcs->disable)
+ iter->funcs->disable(iter);
+ }
- drm_bridge_chain_disable(dsi->bridge);
vc4_dsi_ulps(dsi, true);
- drm_bridge_chain_post_disable(dsi->bridge);
+
+ list_for_each_entry_from(iter, &dsi->bridge_chain, chain_node) {
+ if (iter->funcs->post_disable)
+ iter->funcs->post_disable(iter);
+ }
clk_disable_unprepare(dsi->pll_phy_clock);
clk_disable_unprepare(dsi->escape_clock);
@@ -824,6 +833,7 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)
struct vc4_dsi *dsi = vc4_encoder->dsi;
struct device *dev = &dsi->pdev->dev;
bool debug_dump_regs = false;
+ struct drm_bridge *iter;
unsigned long hs_clock;
u32 ui_ns;
/* Minimum LP state duration in escape clock cycles. */
@@ -1056,7 +1066,10 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)
vc4_dsi_ulps(dsi, false);
- drm_bridge_chain_pre_enable(dsi->bridge);
+ list_for_each_entry_reverse(iter, &dsi->bridge_chain, chain_node) {
+ if (iter->funcs->pre_enable)
+ iter->funcs->pre_enable(iter);
+ }
if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO) {
DSI_PORT_WRITE(DISP0_CTRL,
@@ -1073,7 +1086,10 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)
DSI_DISP0_ENABLE);
}
- drm_bridge_chain_enable(dsi->bridge);
+ list_for_each_entry(iter, &dsi->bridge_chain, chain_node) {
+ if (iter->funcs->enable)
+ iter->funcs->enable(iter);
+ }
if (debug_dump_regs) {
struct drm_printer p = drm_info_printer(&dsi->pdev->dev);
@@ -1613,7 +1629,7 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
* from our driver, since we need to sequence them within the
* encoder's enable/disable paths.
*/
- list_splice(&dsi->encoder->bridge_chain, &dsi->bridge_chain);
+ list_splice_init(&dsi->encoder->bridge_chain, &dsi->bridge_chain);
if (dsi->port == 0)
vc4_debugfs_add_regset32(drm, "dsi0_regs", &dsi->regset);
@@ -1639,7 +1655,7 @@ static void vc4_dsi_unbind(struct device *dev, struct device *master,
* Restore the bridge_chain so the bridge detach procedure can happen
* normally.
*/
- list_splice(&dsi->bridge_chain, &dsi->encoder->bridge_chain);
+ list_splice_init(&dsi->bridge_chain, &dsi->encoder->bridge_chain);
vc4_dsi_encoder_destroy(dsi->encoder);
if (dsi->port == 1)
--
2.23.0
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