linux-kernel - [PATCH 2/2] drm/rockchip: dsi: Force synchronous probe

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Message-Id: <20221019170255.2.I6b985b0ca372b7e35c6d9ea970b24bcb262d4fc1@changeid>
Date:   Wed, 19 Oct 2022 17:03:49 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Heiko Stübner <heiko@...ech.de>
Cc:     dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        Sandy Huang <hjc@...k-chips.com>,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Heiko Stuebner <heiko.stuebner@...obroma-systems.com>,
        Helen Koike <helen.koike@...labora.com>,
        Brian Norris <briannorris@...omium.org>, stable@...r.kernel.org
Subject: [PATCH 2/2] drm/rockchip: dsi: Force synchronous probe

We can't safely probe a dual-DSI display asynchronously
(driver_async_probe='*' or driver_async_probe='dw-mipi-dsi-rockchip'
cmdline), because dw_mipi_dsi_rockchip_find_second() pokes one DSI
device's drvdata from the other device without any locking.

Request synchronous probe, at least until this driver learns some
appropriate locking for dual-DSI initialization.

Cc: <stable@...r.kernel.org>
Signed-off-by: Brian Norris <briannorris@...omium.org>
---

 drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
index d222c6811207..528ddce144e5 100644
--- a/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
@@ -1689,5 +1689,11 @@ struct platform_driver dw_mipi_dsi_rockchip_driver = {
 		.of_match_table = dw_mipi_dsi_rockchip_dt_ids,
 		.pm	= &dw_mipi_dsi_rockchip_pm_ops,
 		.name	= "dw-mipi-dsi-rockchip",
+		/*
+		 * For dual-DSI display, one DSI pokes at the other DSI's
+		 * drvdata in dw_mipi_dsi_rockchip_find_second(). This is not
+		 * safe for asynchronous probe.
+		 */
+		.probe_type = PROBE_FORCE_SYNCHRONOUS,
 	},
 };
-- 
2.38.0.413.g74048e4d9e-goog