Hi Paul,
Thanks for the patch.
Subject: [PATCH v2 11/19] serial: sh: Fix error handling
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@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(-)
diff --git a/drivers/serial/serial_sh.c b/drivers/serial/serial_sh.c index 5e543dbf3d58..2b650d458e71 100644 --- a/drivers/serial/serial_sh.c +++ b/drivers/serial/serial_sh.c @@ -79,10 +79,22 @@ sh_serial_setbrg_generic(struct uart_port *port, int clk, int baudrate)
static void handle_error(struct uart_port *port) {
- sci_in(port, SCxSR);
- sci_out(port, SCxSR, SCxSR_ERROR_CLEAR(port));
- /*
* Most errors are cleared by resetting the relevant error bits tozero
* in the FSR & LSR registers. For each register, a read followed bya
* write is needed according to the relevant datasheets.*/- unsigned short status = sci_in(port, SCxSR);
- sci_out(port, SCxSR, status & ~SCIF_ERRORS); sci_in(port, SCLSR); sci_out(port, SCLSR, 0x00);
- /*
* To clear framing errors, we also need to read and discard a* character.*/- if (status & SCIF_FER)
sci_in(port, SCxRDR);
Do we need to read status again to make sure framing error is cleared?
Cheers, Biju
}
static int serial_raw_putc(struct uart_port *port, const char c)
2.39.2