serial: sh-sci: Update the suspend/resume support

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_save()/sci_console_restore() functions were added. There is no
need to cache/restore the status or FIFO registers. Only the control
registers. The registers that will be saved/restored on suspend/resume are
specified by the struct sci_suspend_regs data structure.

Signed-off-by: Claudiu Beznea <[email protected]>
Reviewed-by: Geert Uytterhoeven <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: claudiubeznea

drivers/tty/serial/sh-sci.c

@@ -104,6 +104,15 @@ struct plat_sci_reg {
 	u8 offset, size;
 };
 
+struct sci_suspend_regs {
+	u16 scsmr;
+	u16 scscr;
+	u16 scfcr;
+	u16 scsptr;
+	u8 scbrr;
+	u8 semr;
+};
+
 struct sci_port_params {
 	const struct plat_sci_reg regs[SCIx_NR_REGS];
 	unsigned int fifosize;
@@ -134,6 +143,8 @@ 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 +164,7 @@ struct sci_port {
 	int				rx_trigger;
 	struct timer_list		rx_fifo_timer;
 	int				rx_fifo_timeout;
+	struct sci_suspend_regs		suspend_regs;
 	u16				hscif_tot;
 
 	bool has_rtscts;
@@ -3374,6 +3386,7 @@ 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);
@@ -3546,22 +3559,76 @@ static int sci_probe(struct platform_device *dev)
 	return 0;
 }
 
+static void sci_console_save(struct sci_port *s)
+{
+	struct sci_suspend_regs *regs = &s->suspend_regs;
+	struct uart_port *port = &s->port;
+
+	if (sci_getreg(port, SCSMR)->size)
+		regs->scsmr = sci_serial_in(port, SCSMR);
+	if (sci_getreg(port, SCSCR)->size)
+		regs->scscr = sci_serial_in(port, SCSCR);
+	if (sci_getreg(port, SCFCR)->size)
+		regs->scfcr = sci_serial_in(port, SCFCR);
+	if (sci_getreg(port, SCSPTR)->size)
+		regs->scsptr = sci_serial_in(port, SCSPTR);
+	if (sci_getreg(port, SCBRR)->size)
+		regs->scbrr = sci_serial_in(port, SCBRR);
+	if (sci_getreg(port, SEMR)->size)
+		regs->semr = sci_serial_in(port, SEMR);
+}
+
+static void sci_console_restore(struct sci_port *s)
+{
+	struct sci_suspend_regs *regs = &s->suspend_regs;
+	struct uart_port *port = &s->port;
+
+	if (sci_getreg(port, SCSMR)->size)
+		sci_serial_out(port, SCSMR, regs->scsmr);
+	if (sci_getreg(port, SCSCR)->size)
+		sci_serial_out(port, SCSCR, regs->scscr);
+	if (sci_getreg(port, SCFCR)->size)
+		sci_serial_out(port, SCFCR, regs->scfcr);
+	if (sci_getreg(port, SCSPTR)->size)
+		sci_serial_out(port, SCSPTR, regs->scsptr);
+	if (sci_getreg(port, SCBRR)->size)
+		sci_serial_out(port, SCBRR, regs->scbrr);
+	if (sci_getreg(port, SEMR)->size)
+		sci_serial_out(port, SEMR, regs->semr);
+}
+
 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_save(sport);
+		else
+			return reset_control_assert(sport->rstc);
+	}
+
 	return 0;
 }
 
 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_restore(sport);
+		} else {
+			int ret = reset_control_deassert(sport->rstc);
+
+			if (ret)
+				return ret;
+		}
+
 		uart_resume_port(&sci_uart_driver, &sport->port);
+	}
 
 	return 0;
 }