From: Kuogee Hsieh quic_khsieh@quicinc.com
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@quicinc.com Tested-by: Douglas Anderson dianders@chromium.org Reviewed-by: Abhinav Kumar quic_abhinavk@quicinc.com Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org Patchwork: https://patchwork.freedesktop.org/patch/516121/ Link: https://lore.kernel.org/r/1672193785-11003-2-git-send-email-quic_khsieh@quic... Signed-off-by: Abhinav Kumar quic_abhinavk@quicinc.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 @@ -406,6 +406,10 @@ void dp_aux_isr(struct drm_dp_aux *dp_au
isr = dp_catalog_aux_get_irq(aux->catalog);
+ /* no interrupts pending, return immediately */ + if (!isr) + return; + if (!aux->cmd_busy) return;