linux-kernel - [PATCH v5 02/10] drm/bridge: it6505: improve AUX operation for edid read

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Message-ID: <20241001064305.32180-3-Hermes.Wu@ite.com.tw>
Date: Tue, 1 Oct 2024 14:43:01 +0800
From: Hermes Wu <Hermes.Wu@....com.tw>
To: Pin-yen Lin <treapking@...omium.org>
CC: Kenneth Hung <Kenneth.hung@....com.tw>, Pet Weng <Pet.Weng@....com.tw>,
        Hermes Wu <Hermes.wu@....com.tw>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman
	<jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maarten
 Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard
	<mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie
	<airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        "open list:DRM DRIVERS"
	<dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: [PATCH v5 02/10] drm/bridge: it6505: improve AUX operation for edid read

From: Hermes Wu <Hermes.wu@....com.tw>

The original AUX operation using data registers is limited to 4 bytes.
The AUX operation command CMD_AUX_I2C_EDID_READ uses AUX FIFO and is capable of reading 16 bytes.
This improves the speed of EDID read.

Signed-off-by: Hermes Wu <Hermes.wu@....com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
index 28a8043229d3..864fab7e388f 100644
--- a/drivers/gpu/drm/bridge/ite-it6505.c
+++ b/drivers/gpu/drm/bridge/ite-it6505.c
@@ -1076,10 +1076,13 @@ static ssize_t it6505_aux_do_transfer(struct it6505 *it6505,
 				      size_t size, enum aux_cmd_reply *reply)
 {
 	int i, ret_size, ret = 0, request_size;
+	int fifo_max_size = (cmd == CMD_AUX_I2C_EDID_READ) ? AUX_FIFO_MAX_SIZE : 4;
 
 	mutex_lock(&it6505->aux_lock);
-	for (i = 0; i < size; i += 4) {
-		request_size = min((int)size - i, 4);
+	i = 0;
+	do {
+		request_size = min_t(int, (int)size - i, fifo_max_size);
+
 		ret_size = it6505_aux_operation(it6505, cmd, address + i,
 						buffer + i, request_size,
 						reply);
@@ -1088,8 +1091,9 @@ static ssize_t it6505_aux_do_transfer(struct it6505 *it6505,
 			goto aux_op_err;
 		}
 
+		i += request_size;
 		ret += ret_size;
-	}
+	} while (i < size);
 
 aux_op_err:
 	mutex_unlock(&it6505->aux_lock);
-- 
2.34.1