From f1a2a9a675899c166a75c6e398af8aa5445e5e5f Mon Sep 17 00:00:00 2001 From: Dave Stevenson Date: Fri, 17 May 2024 14:27:59 +0100 Subject: [PATCH 1092/1135] regulator: rpi_panel_v2: Add delay on I2C reads As with many microcontrollers, the panel wants to use clock stretching during a read so that the appropriate return value can be generated and programmed into the hardware. With Pi0-3 really not supporting clock stretching, this resulted in the panel firmware dying. Insert a delay between the write and the read to give the firmware a chance to generate the relevant return value. Signed-off-by: Dave Stevenson --- drivers/regulator/rpi-panel-v2-regulator.c | 35 +++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) --- a/drivers/regulator/rpi-panel-v2-regulator.c +++ b/drivers/regulator/rpi-panel-v2-regulator.c @@ -87,6 +87,39 @@ static const struct backlight_ops rpi_pa .update_status = rpi_panel_v2_update_status, }; +static int rpi_panel_v2_i2c_read(struct i2c_client *client, u8 reg, unsigned int *buf) +{ + struct i2c_msg msgs[1]; + u8 addr_buf[1] = { reg }; + u8 data_buf[1] = { 0, }; + int ret; + + /* Write register address */ + msgs[0].addr = client->addr; + msgs[0].flags = 0; + msgs[0].len = ARRAY_SIZE(addr_buf); + msgs[0].buf = addr_buf; + + ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); + if (ret != ARRAY_SIZE(msgs)) + return -EIO; + + usleep_range(5000, 10000); + + /* Read data from register */ + msgs[0].addr = client->addr; + msgs[0].flags = I2C_M_RD; + msgs[0].len = 1; + msgs[0].buf = data_buf; + + ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); + if (ret != ARRAY_SIZE(msgs)) + return -EIO; + + *buf = data_buf[0]; + return 0; +} + /* * I2C driver interface functions */ @@ -114,7 +147,7 @@ static int rpi_panel_v2_i2c_probe(struct goto error; } - ret = regmap_read(regmap, REG_ID, &data); + ret = rpi_panel_v2_i2c_read(i2c, REG_ID, &data); if (ret < 0) { dev_err(&i2c->dev, "Failed to read REG_ID reg: %d\n", ret); goto error;