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

Philipp Zabel
2024-11-18T11:52:05Z

On Mo, 2024-11-18 at 11:47 +0200, Claudiu Beznea wrote:
> Hi, Philipp,
>
> On 15.11.2024 17:40, Philipp Zabel wrote:
> > 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?
>
> If I'm not wrongly understanding your question, yes, the
> reset_control_deassert() is still needed in the sci_parse_dt() as the
> sci_parse_dt() is called on probe path. After resume the sci_parse_dt() is
> not called unless the driver is unbinded and then re-binded.

Ah, I was thinking of runtime PM resume callbacks. Thank you for the
answer, this cleared my confusion.

regards
Philipp