linux-kernel - [PATCH 5.4 091/270] drm/bridge: ti-sn65dsi86: Clear old error bits before AUX transfers

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Message-Id: <20200817143800.292421968@linuxfoundation.org>
Date:   Mon, 17 Aug 2020 17:14:52 +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, Douglas Anderson <dianders@...omium.org>,
        Rob Clark <robdclark@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 091/270] drm/bridge: ti-sn65dsi86: Clear old error bits before AUX transfers

From: Douglas Anderson <dianders@...omium.org>

[ Upstream commit baef4d56195b6d6e0f681f6eac03d8c6db011d34 ]

The AUX channel transfer error bits in the status register are latched
and need to be cleared.  Clear them before doing our transfer so we
don't see old bits and get confused.

Without this patch having a single failure would mean that all future
transfers would look like they failed.

Fixes: b814ec6d4535 ("drm/bridge: ti-sn65dsi86: Implement AUX channel")
Signed-off-by: Douglas Anderson <dianders@...omium.org>
Reviewed-by: Rob Clark <robdclark@...il.com>
Signed-off-by: Sam Ravnborg <sam@...nborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200508163314.1.Idfa69d5d3fc9623083c0ff78572fea87dccb199c@changeid
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/bridge/ti-sn65dsi86.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index 0a580957c8cf1..f1de4bb6558ca 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -647,6 +647,12 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux,
 				     buf[i]);
 	}
 
+	/* Clear old status bits before start so we don't get confused */
+	regmap_write(pdata->regmap, SN_AUX_CMD_STATUS_REG,
+		     AUX_IRQ_STATUS_NAT_I2C_FAIL |
+		     AUX_IRQ_STATUS_AUX_RPLY_TOUT |
+		     AUX_IRQ_STATUS_AUX_SHORT);
+
 	regmap_write(pdata->regmap, SN_AUX_CMD_REG, request_val | AUX_CMD_SEND);
 
 	ret = regmap_read_poll_timeout(pdata->regmap, SN_AUX_CMD_REG, val,
-- 
2.25.1