linux-kernel - [PATCH] drm/msm/dp: Only create debugfs for PRIMARY minor

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Date:   Fri, 15 Oct 2021 16:13:07 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Kuogee Hsieh <khsieh@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Abhinav Kumar <abhinavk@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm/msm/dp: Only create debugfs for PRIMARY minor

dpu_kms_debugfs_init() and hence dp_debug_get() gets invoked for each
minor being registered. But dp_debug_get() will allocate a new struct
dp_debug for each call and this will be associated as dp->debug.

As such dp_debug will create debugfs files in both the PRIMARY and the
RENDER minor's debugfs directory, but only the last reference will be
remembered.

The only use of this reference today is in the cleanup path in
dp_display_deinit_sub_modules() and the dp_debug_private object does
outlive the debugfs entries in either case, so there doesn't seem to be
any adverse effects of this, but per the code the current behavior is
unexpected, so change it to only create dp_debug for the PRIMARY minor.

Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 3aa67c53dbc0..06773b58bb60 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -10,6 +10,7 @@
 #include <linux/component.h>
 #include <linux/of_irq.h>
 #include <linux/delay.h>
+#include <drm/drm_file.h>
 #include <drm/drm_panel.h>

 #include "msm_drv.h"
@@ -1463,6 +1464,10 @@ void msm_dp_debugfs_init(struct msm_dp *dp_display, struct drm_minor *minor)
 	dp = container_of(dp_display, struct dp_display_private, dp_display);
 	dev = &dp->pdev->dev;

+	/* Only create one set of debugfs per DP instance */
+	if (minor->type != DRM_MINOR_PRIMARY)
+		return;
+
 	dp->debug = dp_debug_get(dev, dp->panel, dp->usbpd,
 					dp->link, dp->dp_display.connector,
 					minor);
-- 
2.29.2