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

[Chris Paterson]

> From: U-Boot <u-boot-bounces at lists.denx.de> On Behalf Of Paul Barker
> Sent: Monday, October 9, 2023 5:47 PM
> 
> 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>

I've verified that the problem exists on the RZ/G2M hihope-rzg2m board, and that this patch fixes it.

Tested-by: Chris Paterson <chris.paterson2 at renesas.com>

Kind regards, Chris