From: Jan Kundrát jan.kundrat@cesnet.cz
commit 3f42b142ea1171967e40e10e4b0241c0d6d28d41 upstream.
After upgrading from 5.16 to 6.1, our board with a MAX14830 started producing lots of garbage data over UART. Bisection pointed out commit 285e76fc049c as the culprit. That patch tried to replace hand-written code which I added in 2b4bac48c1084 ("serial: max310x: Use batched reads when reasonably safe") with the generic regmap infrastructure for batched operations.
Unfortunately, the `regmap_raw_read` and `regmap_raw_write` which were used are actually functions which perform IO over *multiple* registers. That's not what is needed for accessing these Tx/Rx FIFOs; the appropriate functions are the `_noinc_` versions, not the `_raw_` ones.
Fix this regression by using `regmap_noinc_read()` and `regmap_noinc_write()` along with the necessary `regmap_config` setup; with this patch in place, our board communicates happily again. Since our board uses SPI for talking to this chip, the I2C part is completely untested.
Fixes: 285e76fc049c ("serial: max310x: use regmap methods for SPI batch operations") Cc: stable@vger.kernel.org Reviewed-by: Andy Shevchenko andy.shevchenko@gmail.com Signed-off-by: Jan Kundrát jan.kundrat@cesnet.cz Link: https://lore.kernel.org/r/79db8e82aadb0e174bc82b9996423c3503c8fb37.168073208... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/max310x.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)
--- a/drivers/tty/serial/max310x.c +++ b/drivers/tty/serial/max310x.c @@ -525,6 +525,11 @@ static bool max310x_reg_precious(struct return false; }
+static bool max310x_reg_noinc(struct device *dev, unsigned int reg) +{ + return reg == MAX310X_RHR_REG; +} + static int max310x_set_baud(struct uart_port *port, int baud) { unsigned int mode = 0, div = 0, frac = 0, c = 0, F = 0; @@ -651,14 +656,14 @@ static void max310x_batch_write(struct u { struct max310x_one *one = to_max310x_port(port);
- regmap_raw_write(one->regmap, MAX310X_THR_REG, txbuf, len); + regmap_noinc_write(one->regmap, MAX310X_THR_REG, txbuf, len); }
static void max310x_batch_read(struct uart_port *port, u8 *rxbuf, unsigned int len) { struct max310x_one *one = to_max310x_port(port);
- regmap_raw_read(one->regmap, MAX310X_RHR_REG, rxbuf, len); + regmap_noinc_read(one->regmap, MAX310X_RHR_REG, rxbuf, len); }
static void max310x_handle_rx(struct uart_port *port, unsigned int rxlen) @@ -1468,6 +1473,10 @@ static struct regmap_config regcfg = { .writeable_reg = max310x_reg_writeable, .volatile_reg = max310x_reg_volatile, .precious_reg = max310x_reg_precious, + .writeable_noinc_reg = max310x_reg_noinc, + .readable_noinc_reg = max310x_reg_noinc, + .max_raw_read = MAX310X_FIFO_SIZE, + .max_raw_write = MAX310X_FIFO_SIZE, };
#ifdef CONFIG_SPI_MASTER @@ -1553,6 +1562,10 @@ static struct regmap_config regcfg_i2c = .volatile_reg = max310x_reg_volatile, .precious_reg = max310x_reg_precious, .max_register = MAX310X_I2C_REVID_EXTREG, + .writeable_noinc_reg = max310x_reg_noinc, + .readable_noinc_reg = max310x_reg_noinc, + .max_raw_read = MAX310X_FIFO_SIZE, + .max_raw_write = MAX310X_FIFO_SIZE, };
static const struct max310x_if_cfg max310x_i2c_if_cfg = {