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
Signed-off-by: Jan Kundrát <jan.kundrat@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/tty/serial/max310x.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index c82391c928cb..47520d4a381f 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -529,6 +529,11 @@ static bool max310x_reg_precious(struct device *dev, unsigned int reg)
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;
@@ -658,14 +663,14 @@ static void max310x_batch_write(struct uart_port *port, u8 *txbuf, unsigned int
{
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)
@@ -1480,6 +1485,10 @@ 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
@@ -1565,6 +1574,10 @@ 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 = {
--
2.39.2
