linux-kernel - [PATCH v2] drm/msm/dp: Always clear mask bits to disable interrupts at dp_ctrl_reset_irq

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Message-ID: <1652133608-29247-1-git-send-email-quic_khsieh@quicinc.com>
Date:   Mon, 9 May 2022 15:00:08 -0700
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     <robdclark@...il.com>, <sean@...rly.run>, <swboyd@...omium.org>,
        <dianders@...omium.org>, <vkoul@...nel.org>, <daniel@...ll.ch>,
        <airlied@...ux.ie>, <agross@...nel.org>,
        <dmitry.baryshkov@...aro.org>, <bjorn.andersson@...aro.org>
CC:     <quic_abhinavk@...cinc.com>, <quic_aravindh@...cinc.com>,
        <quic_khsieh@...cinc.com>, <quic_sbillaka@...cinc.com>,
        <freedreno@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] drm/msm/dp: Always clear mask bits to disable interrupts at dp_ctrl_reset_irq_ctrl()

dp_catalog_ctrl_reset() will software reset DP controller. But it will
not reset programmable registers to default value. DP driver still have
to clear mask bits to interrupt status registers to disable interrupts
after software reset of controller. This patch removes the enable flag
condition checking to always clear mask bits of interrupt status
registers to disable interrupts if enable flag is false.

This patch also will fix the potential problem happen at system suspend where
dp_ctrl_reset_irq_ctrl() was called to try to disable HPD related irqs but
the irq is still unmasked unexpectedly and can come in while system are
suspending. This leads to bus hangs if the irq is handled after we power down
the DP hardware because we run the irq handler and access a device register
assuming that no irq could ever come in if we powered down the device. We
don't know when the irq will be handled though, so it's possible the irq is
pending from before we disable the irq in the hardware.

Changes in v2:
-- add more details commit text

Fixes: ba0a422be723 ("drm/msm/dp: do not initialize phy until plugin interrupt received")
Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
---
 drivers/gpu/drm/msm/dp/dp_ctrl.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
index ebd38d7..09475a5 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
@@ -1391,8 +1391,13 @@ void dp_ctrl_reset_irq_ctrl(struct dp_ctrl *dp_ctrl, bool enable)

 	dp_catalog_ctrl_reset(ctrl->catalog);

-	if (enable)
-		dp_catalog_ctrl_enable_irq(ctrl->catalog, enable);
+	/*
+	* all dp controller programmable registers will not
+	* be reset to default value after DP_SW_RESET
+	* therefore interrupt mask bits have to be updated
+	* to enable/disable interrupts
+	*/
+	dp_catalog_ctrl_enable_irq(ctrl->catalog, enable);
 }

 void dp_ctrl_phy_init(struct dp_ctrl *dp_ctrl)
-- 
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