linux-kernel - [v8, PATCH 1/3] drm/dsi: transfer DSI HS packets ending at the same time

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Message-ID: <20220112153639.12343-2-rex-bc.chen@mediatek.com>
Date:   Wed, 12 Jan 2022 23:36:37 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     <chunkuang.hu@...nel.org>, <matthias.bgg@...il.com>,
        <narmstrong@...libre.com>, <robert.foss@...aro.org>,
        <andrzej.hajda@...el.com>, <daniel@...ll.ch>, <airlied@...ux.ie>,
        <p.zabel@...gutronix.de>
CC:     <xji@...logixsemi.com>, <jitao.shi@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        Rex-BC Chen <rex-bc.chen@...iatek.com>
Subject: [v8, PATCH 1/3] drm/dsi: transfer DSI HS packets ending at the same time

Since a HS transmission is composed of an arbitrary number
of bytes that may not be an integer multiple of lanes, some
lanes may run out of data before others.
(Defined in 6.1.3 of mipi_DSI_specification_v.01-02-00)

However, for some DSI RX devices (for example, anx7625),
there is a limitation that packet number should be the same
on all DSI lanes. In other words, they need to end a HS at
the same time.

Because this limitation is for some specific DSI RX devices,
it is more reasonable to put the enable control in these
DSI RX drivers. If DSI TX driver knows the information,
they can adjust the setting for this situation.

Therefore, add a flag to control this situation beacuse the
mipi DSI specification is not forbidden this situation.

Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
Reviewed-by: Chun-Kuang Hu <chunkuang.hu@...nel.org>
---
 include/drm/drm_mipi_dsi.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 147e51b6d241..df4d15345326 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -177,6 +177,8 @@ struct mipi_dsi_device_info {
  * @lp_rate: maximum lane frequency for low power mode in hertz, this should
  * be set to the real limits of the hardware, zero is only accepted for
  * legacy drivers
+ * @hs_packet_end_aligned: transfer DSI HS packets ending at the same time
+ * for all DSI lanes
  */
 struct mipi_dsi_device {
 	struct mipi_dsi_host *host;
@@ -189,6 +191,7 @@ struct mipi_dsi_device {
 	unsigned long mode_flags;
 	unsigned long hs_rate;
 	unsigned long lp_rate;
+	bool hs_packet_end_aligned;
 };

 #define MIPI_DSI_MODULE_PREFIX "mipi-dsi:"
-- 
2.18.0