This is a note to let you know that I've just added the patch titled drm/msm/dp: do not complete dp_aux_cmd_fifo_tx() if irq is not for aux transfer to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-msm-dp-do-not-complete-dp_aux_cmd_fifo_tx-if-irq-is-not-for-aux-transfer.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 1cba0d150fa102439114a91b3e215909efc9f169 Mon Sep 17 00:00:00 2001 From: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx> Date: Tue, 27 Dec 2022 18:16:24 -0800 Subject: drm/msm/dp: do not complete dp_aux_cmd_fifo_tx() if irq is not for aux transfer From: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx> commit 1cba0d150fa102439114a91b3e215909efc9f169 upstream. There are 3 possible interrupt sources are handled by DP controller, HPDstatus, Controller state changes and Aux read/write transaction. At every irq, DP controller have to check isr status of every interrupt sources and service the interrupt if its isr status bits shows interrupts are pending. There is potential race condition may happen at current aux isr handler implementation since it is always complete dp_aux_cmd_fifo_tx() even irq is not for aux read or write transaction. This may cause aux read transaction return premature if host aux data read is in the middle of waiting for sink to complete transferring data to host while irq happen. This will cause host's receiving buffer contains unexpected data. This patch fixes this problem by checking aux isr and return immediately at aux isr handler if there are no any isr status bits set. Current there is a bug report regrading eDP edid corruption happen during system booting up. After lengthy debugging to found that VIDEO_READY interrupt was continuously firing during system booting up which cause dp_aux_isr() to complete dp_aux_cmd_fifo_tx() prematurely to retrieve data from aux hardware buffer which is not yet contains complete data transfer from sink. This cause edid corruption. Follows are the signature at kernel logs when problem happen, EDID has corrupt header panel-simple-dp-aux aux-aea0000.edp: Couldn't identify panel via EDID Changes in v2: -- do complete if (ret == IRQ_HANDLED) ay dp-aux_isr() -- add more commit text Changes in v3: -- add Stephen suggested -- dp_aux_isr() return IRQ_XXX back to caller -- dp_ctrl_isr() return IRQ_XXX back to caller Changes in v4: -- split into two patches Changes in v5: -- delete empty line between tags Changes in v6: -- remove extra "that" and fixed line more than 75 char at commit text Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support") Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx> Tested-by: Douglas Anderson <dianders@xxxxxxxxxxxx> Reviewed-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> Patchwork: https://patchwork.freedesktop.org/patch/516121/ Link: https://lore.kernel.org/r/1672193785-11003-2-git-send-email-quic_khsieh@xxxxxxxxxxx Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/msm/dp/dp_aux.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/drivers/gpu/drm/msm/dp/dp_aux.c +++ b/drivers/gpu/drm/msm/dp/dp_aux.c @@ -423,6 +423,10 @@ void dp_aux_isr(struct drm_dp_aux *dp_au aux->isr = dp_catalog_aux_get_irq(aux->catalog); + /* no interrupts pending, return immediately */ + if (!isr) + return; + if (!aux->cmd_busy) return; Patches currently in stable-queue which might be from quic_khsieh@xxxxxxxxxxx are queue-5.10/drm-msm-dp-do-not-complete-dp_aux_cmd_fifo_tx-if-irq-is-not-for-aux-transfer.patch