Re: [PATCH] serial: max310x: fix IO data corruption in batched operations

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Wed, Apr 05, 2023 at 10:14:23PM +0200, Jan Kundrát wrote:
> 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

Nit, please use the style that the documentation asks for here, which
should look like:

Fixes: 285e76fc049c ("serial: max310x: use regmap methods for SPI batch operations")

otherwise our tools complain :(
I'll go fix this up by hand...

greg k-h