linux-kernel - [PATCH 5.6 201/254] drm/bridge: analogix-anx78xx: Fix drm_dp

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Date:   Thu, 16 Apr 2020 15:24:50 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Torsten Duwe <duwe@....de>,
        Thierry Reding <treding@...dia.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        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>,
        Thomas Zimmermann <tzimmermann@...e.de>
Subject: [PATCH 5.6 201/254] drm/bridge: analogix-anx78xx: Fix drm_dp_link helper removal

From: Torsten Duwe <duwe@....de>

commit 3e138a63d6674a4567a018a31e467567c40b14d5 upstream.

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@....de>
Fixes: ff1e8fb68ea0 ("drm/bridge: analogix-anx78xx: Avoid drm_dp_link helpers")
Cc: Thierry Reding <treding@...dia.com>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Andrzej Hajda <a.hajda@...sung.com>
Cc: Neil Armstrong <narmstrong@...libre.com>
Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
Cc: Jonas Karlman <jonas@...boo.se>
Cc: Jernej Skrabec <jernej.skrabec@...l.net>
Cc: <stable@...r.kernel.org> # v5.5+
Reviewed-by: Thierry Reding <treding@...dia.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@...e.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20200218155744.9675368BE1@verein.lst.de
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- 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(stru
 	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;