linux-kernel - [RESEND][PATCH] drm/bridge: analogix-anx78xx: Fix drm_dp

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Date:   Tue, 18 Feb 2020 16:47:42 +0100 (CET)
From:   Torsten Duwe <duwe@....de>
To:     Thierry Reding <thierry.reding@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Maxime Ripard <maxime@...no.tech>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [RESEND][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.

fixes: ff1e8fb68ea06027 ("analogix-anx78xx: Avoid drm_dp_link helpers")
Signed-off-by: Torsten Duwe <duwe@...e.de>
---
https://patchwork.freedesktop.org/patch/343003/
https://lists.freedesktop.org/archives/dri-devel/2020-January/253535.html

---
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;