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58 lines
1.9 KiB
Diff
58 lines
1.9 KiB
Diff
From d35c4135f30c306174b6a122f2f7e51ee604ae43 Mon Sep 17 00:00:00 2001
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From: Dave Stevenson <dave.stevenson@raspberrypi.com>
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Date: Thu, 23 Apr 2020 10:17:18 +0100
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Subject: [PATCH] drm/panel/raspberrypi-touchscreen: Use independent I2C
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actions with delay.
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We now have the hardware I2C controller pinmuxed to the drive the
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display I2C, but this controller does not support clock stretching.
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The Atmel micro-controller in the panel requires clock stretching
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to allow it to prepare any data to be read.
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Split the rpi_touchscreen_i2c_read into two independent transactions with
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a delay between them for the Atmel to prepare the data.
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Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
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---
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.../drm/panel/panel-raspberrypi-touchscreen.c | 30 ++++++++++++++++++-
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1 file changed, 29 insertions(+), 1 deletion(-)
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--- a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
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+++ b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
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@@ -220,7 +220,35 @@ static struct rpi_touchscreen *panel_to_
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static int rpi_touchscreen_i2c_read(struct rpi_touchscreen *ts, u8 reg)
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{
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- return i2c_smbus_read_byte_data(ts->i2c, reg);
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+ struct i2c_client *client = ts->i2c;
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+ struct i2c_msg msgs[1];
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+ u8 addr_buf[1] = { reg };
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+ u8 data_buf[1] = { 0, };
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+ int ret;
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+
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+ /* Write register address */
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+ msgs[0].addr = client->addr;
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+ msgs[0].flags = 0;
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+ msgs[0].len = ARRAY_SIZE(addr_buf);
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+ msgs[0].buf = addr_buf;
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+
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+ ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
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+ if (ret != ARRAY_SIZE(msgs))
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+ return -EIO;
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+
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+ usleep_range(100, 300);
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+
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+ /* Read data from register */
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+ msgs[0].addr = client->addr;
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+ msgs[0].flags = I2C_M_RD;
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+ msgs[0].len = 1;
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+ msgs[0].buf = data_buf;
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+
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+ ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
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+ if (ret != ARRAY_SIZE(msgs))
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+ return -EIO;
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+
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+ return data_buf[0];
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}
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static void rpi_touchscreen_i2c_write(struct rpi_touchscreen *ts,
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