Re: [PATCH v3 3/8] serial: sh-sci: Update the suspend/resume support

Philipp Zabel
2024-11-15T15:41:12Z

On Fr, 2024-11-15 at 15:43 +0200, Claudiu wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>
> The Renesas RZ/G3S supports a power saving mode where power to most of the
> SoC components is turned off. When returning from this power saving mode,
> SoC components need to be re-configured.
>
> The SCIFs on the Renesas RZ/G3S need to be re-configured as well when
> returning from this power saving mode. The sh-sci code already configures
> the SCIF clocks, power domain and registers by calling uart_resume_port()
> in sci_resume(). On suspend path the SCIF UART ports are suspended
> accordingly (by calling uart_suspend_port() in sci_suspend()). The only
> missing setting is the reset signal. For this assert/de-assert the reset
> signal on driver suspend/resume.
>
> In case the no_console_suspend is specified by the user, the registers need
> to be saved on suspend path and restore on resume path. To do this the
> sci_console_setup() function was added. There is no need to cache/restore
> the status or FIFO registers. Only the control registers. To differentiate
> b/w these, the struct sci_port_params::regs was updated with a new member
> that specifies if the register needs to be chached on suspend. Only the
> RZ_SCIFA instances were updated with this new support as the hardware for
> the rest of variants was missing for testing.
>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
> ---
>
> Changes in v3:
> - none
>
> Changes in v2:
> - rebased on top of the update version of patch 2/8 from
> this series
>
> drivers/tty/serial/sh-sci.c | 53 ++++++++++++++++++++++++++++++-------
> 1 file changed, 44 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> index ade151ff39d2..e53496d2708e 100644
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -101,7 +101,7 @@ enum SCI_CLKS {
> if ((_port)->sampling_rate_mask & SCI_SR((_sr)))
>
> struct plat_sci_reg {
> - u8 offset, size;
> + u8 offset, size, suspend_cacheable;
> };
>
> struct sci_port_params {
> @@ -134,6 +134,8 @@ struct sci_port {
> struct dma_chan *chan_tx;
> struct dma_chan *chan_rx;
>
> + struct reset_control *rstc;
> +
> #ifdef CONFIG_SERIAL_SH_SCI_DMA
> struct dma_chan *chan_tx_saved;
> struct dma_chan *chan_rx_saved;
> @@ -153,6 +155,7 @@ struct sci_port {
> int rx_trigger;
> struct timer_list rx_fifo_timer;
> int rx_fifo_timeout;
> + unsigned int console_cached_regs[SCIx_NR_REGS];
> u16 hscif_tot;
>
> bool has_rtscts;
> @@ -298,17 +301,17 @@ static const struct sci_port_params sci_port_params[SCIx_NR_REGTYPES] = {
> */
> [SCIx_RZ_SCIFA_REGTYPE] = {
> .regs = {
> - [SCSMR] = { 0x00, 16 },
> - [SCBRR] = { 0x02, 8 },
> - [SCSCR] = { 0x04, 16 },
> + [SCSMR] = { 0x00, 16, 1 },
> + [SCBRR] = { 0x02, 8, 1 },
> + [SCSCR] = { 0x04, 16, 1 },
> [SCxTDR] = { 0x06, 8 },
> [SCxSR] = { 0x08, 16 },
> [SCxRDR] = { 0x0A, 8 },
> - [SCFCR] = { 0x0C, 16 },
> + [SCFCR] = { 0x0C, 16, 1 },
> [SCFDR] = { 0x0E, 16 },
> - [SCSPTR] = { 0x10, 16 },
> + [SCSPTR] = { 0x10, 16, 1 },
> [SCLSR] = { 0x12, 16 },
> - [SEMR] = { 0x14, 8 },
> + [SEMR] = { 0x14, 8, 1 },
> },
> .fifosize = 16,
> .overrun_reg = SCLSR,
> @@ -3380,6 +3383,7 @@ static struct plat_sci_port *sci_parse_dt(struct platform_device *pdev,
> }
>
> sp = &sci_ports[id];
> + sp->rstc = rstc;
> *dev_id = id;
>
> p->type = SCI_OF_TYPE(data);
> @@ -3507,13 +3511,34 @@ static int sci_probe(struct platform_device *dev)
> return 0;
> }
>
> +static void sci_console_setup(struct sci_port *s, bool save)
> +{
> + for (u16 i = 0; i < SCIx_NR_REGS; i++) {
> + struct uart_port *port = &s->port;
> +
> + if (!s->params->regs[i].suspend_cacheable)
> + continue;
> +
> + if (save)
> + s->console_cached_regs[i] = sci_serial_in(port, i);
> + else
> + sci_serial_out(port, i, s->console_cached_regs[i]);
> + }
> +}
> +
> static __maybe_unused int sci_suspend(struct device *dev)
> {
> struct sci_port *sport = dev_get_drvdata(dev);
>
> - if (sport)
> + if (sport) {
> uart_suspend_port(&sci_uart_driver, &sport->port);
>
> + if (!console_suspend_enabled && uart_console(&sport->port))
> + sci_console_setup(sport, true);
> + else
> + return reset_control_assert(sport->rstc);
> + }
> +
> return 0;
> }
>
> @@ -3521,8 +3546,18 @@ static __maybe_unused int sci_resume(struct device *dev)
> {
> struct sci_port *sport = dev_get_drvdata(dev);
>
> - if (sport)
> + if (sport) {
> + if (!console_suspend_enabled && uart_console(&sport->port)) {
> + sci_console_setup(sport, false);
> + } else {
> + int ret = reset_control_deassert(sport->rstc);

With this, is the reset_control_deassert() in sci_parse_dt() still
needed?

Likewise, does the reset_control_assert() in sci_suspend() remove the
need for the sci_reset_control_assert() devm action?

regards
Philipp