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

[Claudiu Beznea <claudiu.beznea@tuxon.dev>]

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.

In case the reset_control_dessert() here fails (or not) and an
unbind/re-bind will be requested, the unbind will call
reset_control_assert() (though the devm action) and then the re-bind will
call reset_control_deassert() though sci_parse_dt(). That should be safe,
AFAICT.


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

No, the sci_reset_control_assert() is still needed as explained above,
unless I missed your point.

Please let me know if missed your point and/or answered your question?


Thank you,
Claudiu Beznea

> 
> regards
> Philipp