linux-kernel - [PATCH v8 18/19] drm/mediatek: change the aux retries times when receiving AUX

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Date:   Fri, 18 Feb 2022 15:54:36 +0100
From:   Guillaume Ranquet <granquet@...libre.com>
To:     chunkuang.hu@...nel.org, p.zabel@...gutronix.de, airlied@...ux.ie,
        daniel@...ll.ch, robh+dt@...nel.org,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, matthias.bgg@...il.com,
        chunfeng.yun@...iatek.com, kishon@...com, vkoul@...nel.org,
        deller@....de, ck.hu@...iatek.com, jitao.shi@...iatek.com,
        angelogioacchino.delregno@...labora.com
Cc:     dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-phy@...ts.infradead.org, linux-fbdev@...r.kernel.org
Subject: [PATCH v8 18/19] drm/mediatek: change the aux retries times when receiving AUX_DEFER

From: Jitao Shi <jitao.shi@...iatek.com>

DP 1.4a Section 2.8.7.1.5.6.1:
A DP Source device shall retry at least seven times upon receiving
AUX_DEFER before giving up the AUX transaction.

Aux should retry to send msg whether how many bytes.

Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index fe91ab8b2fd89..4e880d8a8a186 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -1879,7 +1879,7 @@ static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,
 	bool is_read;
 	u8 request;
 	size_t accessed_bytes = 0;
-	int retry = 3, ret = 0;
+	int retry, ret = 0;
 
 	mtk_dp = container_of(mtk_aux, struct mtk_dp, aux);
 
@@ -1913,15 +1913,21 @@ static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,
 	}
 
 	if (msg->size == 0) {
-		ret = mtk_dp_aux_do_transfer(mtk_dp, is_read, request,
-					     msg->address + accessed_bytes,
-					     msg->buffer + accessed_bytes, 0);
+		retry = 7;
+		while (retry--) {
+			ret = mtk_dp_aux_do_transfer(mtk_dp, is_read, request,
+						     msg->address + accessed_bytes,
+						     msg->buffer + accessed_bytes, 0);
+			if (ret == 0)
+				break;
+			msleep(50);
 		}
 	} else {
 		while (accessed_bytes < msg->size) {
 			size_t to_access =
 				min_t(size_t, DP_AUX_MAX_PAYLOAD_BYTES,
 				      msg->size - accessed_bytes);
+			retry = 7;
 			while (retry--) {
 				ret = mtk_dp_aux_do_transfer(mtk_dp,
 							     is_read, request,
-- 
2.34.1