[PATCH v2 11/19] serial: sh: Fix error handling

[Marek Vasut]

On 10/9/23 18:46, Paul Barker wrote:
> The current SCIF error handling is broken for the RZ/G2L. After a break
> condition has been triggered, the current code is unable to clear the
> error and serial port output never resumes.
> 
> The RZ/G2L datasheet says that most error conditions are cleared by
> resetting the relevant error bits in the FSR & LSR registers to zero.
> To clear framing errors, the invalid data also needs to be read out of
> the receive FIFO.
> 
> After reviewing datasheets for RZ/G2{H,M,N,E}, R-Car Gen4, R-Car Gen3
> and even SH7751 SoCs, it's clear that this is the way to clear errors
> for all of these SoCs.
> 
> While we're here, annotate the handle_error() function with a couple of
> comments as the reads and writes themselves don't immediately make it
> clear what we're doing.
> 
> Signed-off-by: Paul Barker <paul.barker.ct at bp.renesas.com>
> ---
> v1->v2:
>    * New patch after discussion with Marek & further investigation.
> 
> I'm not going to put a `Fixes` tag on this, the error handling has been
> writing ones to clear errors since at least 2007 so maybe it was
> originally right for some board. It doesn't seem to apply to any of the
> current users of the SCIF driver though.
> 
>   drivers/serial/serial_sh.c | 16 ++++++++++++++--
>   1 file changed, 14 insertions(+), 2 deletions(-)

Tested-by: Marek Vasut <marek.vasut+renesas at mailbox.org> # R-Car H3 
Salvator-XS