linux-kernel - [PATCH] drm/sun4i: dsi: Avoid hotplug race with DRM driver bind

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Date:   Mon, 17 Feb 2020 00:09:06 -0600
From:   Samuel Holland <samuel@...lland.org>
To:     Maxime Ripard <mripard@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Samuel Holland <samuel@...lland.org>
Subject: [PATCH] drm/sun4i: dsi: Avoid hotplug race with DRM driver bind

We need to make sure that the DRM driver is fully registered before
allowing the panel to be attached. Otherwise, we may trigger a hotplug
event before sun4i_framebuffer_init() sets up drm->mode_config.funcs,
causing a NULL pointer dereference.

Fixes: 1a2703bd7356 ("drm/sun4i: dsi: Allow binding the host without a panel")
Signed-off-by: Samuel Holland <samuel@...lland.org>
---

This fixes a bug in my previous patch series, that I didn't catch until
it was already merged.

---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 9aa78c73873c..9cc1bb69fcda 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -970,7 +970,7 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
 
 	if (IS_ERR(panel))
 		return PTR_ERR(panel);
-	if (!dsi->drm)
+	if (!dsi->drm || !dsi->drm->registered)
 		return -EPROBE_DEFER;
 
 	dsi->panel = panel;
-- 
2.24.1