The patch below does not apply to the 5.5-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3e138a63d6674a4567a018a31e467567c40b14d5 Mon Sep 17 00:00:00 2001

From: Torsten Duwe duwe@lst.de Date: Tue, 18 Feb 2020 16:57:44 +0100 Subject: [PATCH] drm/bridge: analogix-anx78xx: Fix drm_dp_link helper removal

drm_dp_link_rate_to_bw_code and ...bw_code_to_link_rate simply divide by and multiply with 27000, respectively. Avoid an overflow in the u8 dpcd[0] and the multiply+divide alltogether.

Signed-off-by: Torsten Duwe duwe@lst.de Fixes: ff1e8fb68ea0 ("drm/bridge: analogix-anx78xx: Avoid drm_dp_link helpers") Cc: Thierry Reding treding@nvidia.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Andrzej Hajda a.hajda@samsung.com Cc: Neil Armstrong narmstrong@baylibre.com Cc: Laurent Pinchart Laurent.pinchart@ideasonboard.com Cc: Jonas Karlman jonas@kwiboo.se Cc: Jernej Skrabec jernej.skrabec@siol.net Cc: stable@vger.kernel.org # v5.5+ Reviewed-by: Thierry Reding treding@nvidia.com Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Link: https://patchwork.freedesktop.org/patch/msgid/20200218155744.9675368BE1@vere...

diff --git a/drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c b/drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c index 41867be03751..864423f59d66 100644 --- a/drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c +++ b/drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c @@ -722,10 +722,9 @@ static int anx78xx_dp_link_training(struct anx78xx *anx78xx) if (err) return err;

- dpcd[0] = drm_dp_max_link_rate(anx78xx->dpcd); - dpcd[0] = drm_dp_link_rate_to_bw_code(dpcd[0]); err = regmap_write(anx78xx->map[I2C_IDX_TX_P0], - SP_DP_MAIN_LINK_BW_SET_REG, dpcd[0]); + SP_DP_MAIN_LINK_BW_SET_REG, + anx78xx->dpcd[DP_MAX_LINK_RATE]); if (err) return err;