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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>
69 lines
1.9 KiB
Diff
69 lines
1.9 KiB
Diff
From de0ad7df43a7399f9c09394b35d74bc75ebc60a4 Mon Sep 17 00:00:00 2001
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From: Dave Stevenson <dave.stevenson@raspberrypi.com>
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Date: Thu, 25 Nov 2021 14:50:10 +0000
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Subject: [PATCH] regulator/rpi-panel-attiny: Use two transactions for
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I2C read
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The I2C to the Atmel is very fussy, and locks up easily on
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Pi0-3 particularly on reads.
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If running at 100kHz on Pi3, reading the ID register generally
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locks up the Atmel, but splitting the register select write and
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read into two transactions is reliable.
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Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
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---
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.../regulator/rpi-panel-attiny-regulator.c | 35 ++++++++++++++++++-
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1 file changed, 34 insertions(+), 1 deletion(-)
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--- a/drivers/regulator/rpi-panel-attiny-regulator.c
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+++ b/drivers/regulator/rpi-panel-attiny-regulator.c
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@@ -234,6 +234,39 @@ static void attiny_gpio_set(struct gpio_
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mutex_unlock(&state->lock);
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}
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+static int attiny_i2c_read(struct i2c_client *client, u8 reg, unsigned int *buf)
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+{
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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(5000, 10000);
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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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+ *buf = data_buf[0];
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+ return 0;
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+}
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+
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/*
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* I2C driver interface functions
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*/
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@@ -264,7 +297,7 @@ static int attiny_i2c_probe(struct i2c_c
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goto error;
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}
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- ret = regmap_read(regmap, REG_ID, &data);
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+ ret = attiny_i2c_read(i2c, REG_ID, &data);
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if (ret < 0) {
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dev_err(&i2c->dev, "Failed to read REG_ID reg: %d\n", ret);
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goto error;
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