From 033bfe7538a1523f36dd434eaff7c754a555c458 Mon Sep 17 00:00:00 2001 From: Boris Brezillon Date: Fri, 27 Dec 2019 15:41:23 +0100 Subject: [PATCH] drm/vc4: dsi: Fix bridge chain handling 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 Cc: Eric Anholt Fixes: 05193dc38197 ("drm/bridge: Make the bridge chain a double-linked list") Signed-off-by: Boris Brezillon Reviewed-by: Andrzej Hajda Acked-by: Eric Anholt Link: https://patchwork.freedesktop.org/patch/msgid/20191227144124.210294-2-boris.brezillon@collabora.com --- 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)