Re: [PATCH 07/16] xen/char: implement suspend/resume calls for SCIF driver

[Mykola Kvach <xakep.amatop@xxxxxxxxx>]

Hi,

On Wed, Mar 19, 2025 at 7:21 PM Grygorii Strashko
<grygorii_strashko@xxxxxxxx> wrote:
>
>
>
> On 05.03.25 11:11, Mykola Kvach wrote:
> > From: Mykola Kvach <mykola_kvach@xxxxxxxx>
> >
> > The changes have been tested only on the Renesas R-Car-H3 Starter Kit board.
> >
> > Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
> > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> > Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
> > ---
> >   xen/drivers/char/scif-uart.c | 31 ++++++++++++++++++++++++++++++-
> >   1 file changed, 30 insertions(+), 1 deletion(-)
> >
> > diff --git a/xen/drivers/char/scif-uart.c b/xen/drivers/char/scif-uart.c
> > index 757793ca45..e166fb0f36 100644
> > --- a/xen/drivers/char/scif-uart.c
> > +++ b/xen/drivers/char/scif-uart.c
> > @@ -139,7 +139,7 @@ static void scif_uart_interrupt(int irq, void *data)
> >       }
> >   }
> >
> > -static void __init scif_uart_init_preirq(struct serial_port *port)
> > +static void scif_uart_init_preirq(struct serial_port *port)
> >   {
> >       struct scif_uart *uart = port->uart;
> >       const struct port_params *params = uart->params;
> > @@ -271,6 +271,33 @@ static void scif_uart_stop_tx(struct serial_port *port)
> >       scif_writew(uart, SCIF_SCSCR, scif_readw(uart, SCIF_SCSCR) & 
> > ~SCSCR_TIE);
> >   }
> >
>
> I assume you want ifdef CONFIG_SYSTEM_SUSPEND here also

I was thinking about it and decided that since we have the
suspend/resume fields uncovered for uart_driver,
I'll leave the functions uncovered as well.

I'll add coverage in the next patch series.
It’s probably needed to cover the suspend/resume fields too, but that
will require additional changes for other UART drivers.
Thank you for pointing that out.

>
>
> > +static void scif_uart_suspend(struct serial_port *port)
> > +{
> > +    struct scif_uart *uart = port->uart;
> > +
> > +    scif_uart_stop_tx(port);
> > +
> > +    /* Wait until last bit has been transmitted. */
> > +    while ( !(scif_readw(uart, SCIF_SCFSR) & SCFSR_TEND) );
> > +
> > +    /* Disable TX/RX parts and all interrupts */
> > +    scif_writew(uart, SCIF_SCSCR, 0);
> > +
> > +    /* Reset TX/RX FIFOs */
> > +    scif_writew(uart, SCIF_SCFCR, SCFCR_RFRST | SCFCR_TFRST);
> > +}
> > +
> > +static void scif_uart_resume(struct serial_port *port)
> > +{
> > +    struct scif_uart *uart = port->uart;
> > +
> > +    scif_uart_init_preirq(port);
> > +
> > +    /* Enable TX/RX and Error Interrupts  */
> > +    scif_writew(uart, SCIF_SCSCR, scif_readw(uart, SCIF_SCSCR) |
> > +                SCSCR_TIE | SCSCR_RIE | SCSCR_REIE);
> > +}
> > +
> >   static struct uart_driver __read_mostly scif_uart_driver = {
> >       .init_preirq  = scif_uart_init_preirq,
> >       .init_postirq = scif_uart_init_postirq,
> > @@ -281,6 +308,8 @@ static struct uart_driver __read_mostly 
> > scif_uart_driver = {
> >       .start_tx     = scif_uart_start_tx,
> >       .stop_tx      = scif_uart_stop_tx,
> >       .vuart_info   = scif_vuart_info,
> > +    .suspend      = scif_uart_suspend,
> > +    .resume       = scif_uart_resume,
> >   };
> >
> >   static const struct dt_device_match scif_uart_dt_match[] __initconst =
>
> --
> Best regards,
> -grygorii

Best regards,
Mykola