20ea6adbf1
Build system: x86_64 Build-tested: bcm2708, bcm2709, bcm2710, bcm2711 Run-tested: bcm2708/RPiB+, bcm2709/RPi3B, bcm2710/RPi3B, bcm2711/RPi4B Signed-off-by: Marty Jones <mj8263788@gmail.com> Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
59 lines
1.9 KiB
Diff
59 lines
1.9 KiB
Diff
From 41fa219f0276c70226ac097daaa1b485818bb82a 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
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I2C 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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@@ -219,7 +219,35 @@ 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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