[v2,3/8] serial: sh-sci: Update the suspend/resume support

Commit Message

Claudiu Beznea Nov. 8, 2024, 10:05 a.m. UTC

From: Claudiu Beznea <[e-mail]>

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 <[e-mail]>
---

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(-)

Patch

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 65514d37bfe2..efac65bb8809 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,
@@ -3365,6 +3368,7 @@  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);
@@ -3492,13 +3496,34 @@  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;
 }
 
@@ -3506,8 +3531,18 @@  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);
+
+			if (ret)
+				return ret;
+		}
+
 		uart_resume_port(&sci_uart_driver, &sport->port);
+	}
 
 	return 0;
 }