Re: [PATCH v5] xen/char: implement suspend/resume calls for SCIF driver

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

On 07.08.25 08:16, Mykola Kvach wrote:


Hello Mykola,

In general patch looks good to me, just one question below ...

> From: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
>
> Implement suspend and resume callbacks for the SCIF UART driver,
> enabled when CONFIG_SYSTEM_SUSPEND is set. This allows proper
> handling of UART state across system suspend/resume cycles.
>
> Tested on Renesas R-Car H3 Starter Kit.
>
> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
> ---
> In patch v5, there are no changes at all;
> it was done just to trigger a review.
I think, you could ping on V4.


> In patch v4, enhance commit message, no functional changes
>
> In patch v2, I just added a CONFIG_SYSTEM_SUSPEND check around
> the suspend/resume functions in the SCIF driver.
> ---
>   xen/drivers/char/scif-uart.c | 40 ++++++++++++++++++++++++++++++++++--
>   1 file changed, 38 insertions(+), 2 deletions(-)
>
> diff --git a/xen/drivers/char/scif-uart.c b/xen/drivers/char/scif-uart.c
> index 757793ca45..888821a3b8 100644
> --- a/xen/drivers/char/scif-uart.c
> +++ b/xen/drivers/char/scif-uart.c
> @@ -139,9 +139,8 @@ static void scif_uart_interrupt(int irq, void *data)
>       }
>   }
>   
> -static void __init scif_uart_init_preirq(struct serial_port *port)
> +static void scif_uart_disable(struct scif_uart *uart)
>   {
> -    struct scif_uart *uart = port->uart;
>       const struct port_params *params = uart->params;
>   
>       /*
> @@ -155,6 +154,14 @@ static void __init scif_uart_init_preirq(struct 
> serial_port *port)
>   
>       /* Reset TX/RX FIFOs */
>       scif_writew(uart, SCIF_SCFCR, SCFCR_RFRST | SCFCR_TFRST);
> +}
> +
> +static void scif_uart_init_preirq(struct serial_port *port)
> +{
> +    struct scif_uart *uart = port->uart;
> +    const struct port_params *params = uart->params;
> +
> +    scif_uart_disable(uart);
>   
>       /* Clear all errors and flags */
>       scif_readw(uart, params->status_reg);
> @@ -271,6 +278,31 @@ static void scif_uart_stop_tx(struct serial_port *port)
>       scif_writew(uart, SCIF_SCSCR, scif_readw(uart, SCIF_SCSCR) & ~SCSCR_TIE);
>   }
>   
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +
> +static void scif_uart_suspend(struct serial_port *port)
> +{
> +    struct scif_uart *uart = port->uart;
> +
> +    scif_uart_stop_tx(port);
 ... I wonder, whether the call above (that disables Transmit 
interrupt) is really needed as the call below disables all interrupts 
anyway?

> +    scif_uart_disable(uart);
> +}
[snip]