linux-kernel - [PATCH AUTOSEL 6.14 636/642] serial: sh-sci: Save and restore more registers

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Message-Id: <20250505221419.2672473-636-sashal@kernel.org>
Date: Mon,  5 May 2025 18:14:12 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Geert Uytterhoeven <geert+renesas@...der.be>,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sasha Levin <sashal@...nel.org>,
	jirislaby@...nel.org,
	wsa+renesas@...g-engineering.com,
	zack.rusin@...adcom.com,
	namcao@...utronix.de,
	prabhakar.mahadev-lad.rj@...renesas.com,
	linux-serial@...r.kernel.org
Subject: [PATCH AUTOSEL 6.14 636/642] serial: sh-sci: Save and restore more registers

From: Geert Uytterhoeven <geert+renesas@...der.be>

[ Upstream commit 81100b9a7b0515132996d62a7a676a77676cb6e3 ]

On (H)SCIF with a Baud Rate Generator for External Clock (BRG), there
are multiple ways to configure the requested serial speed.  If firmware
uses a different method than Linux, and if any debug info is printed
after the Bit Rate Register (SCBRR) is restored, but before termios is
reconfigured (which configures the alternative method), the system may
lock-up during resume.

Fix this by saving and restoring the contents of the BRG Frequency
Division (SCDL) and Clock Select (SCCKS) registers as well.

Also save and restore the HSCIF's Sampling Rate Register (HSSRR), which
configures the sampling point, and the SCIFA/SCIFB's Serial Port Control
and Data Registers (SCPCR/SCPDR), which configure the optional control
flow signals.

After this, all registers that are not saved/restored are either:
  - read-only,
  - write-only,
  - status registers containing flags with clear-after-set semantics,
  - FIFO Data Count Trigger registers, which do not matter much for
    the serial console.

Fixes: 22a6984c5b5df8ea ("serial: sh-sci: Update the suspend/resume support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
Tested-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Link: https://lore.kernel.org/r/11c2eab45d48211e75d8b8202cce60400880fe55.1741114989.git.geert+renesas@glider.be
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/serial/sh-sci.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index e0ead0147bfe0..0219135caafa4 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -105,10 +105,15 @@ struct plat_sci_reg {
 };
 
 struct sci_suspend_regs {
+	u16 scdl;
+	u16 sccks;
 	u16 scsmr;
 	u16 scscr;
 	u16 scfcr;
 	u16 scsptr;
+	u16 hssrr;
+	u16 scpcr;
+	u16 scpdr;
 	u8 scbrr;
 	u8 semr;
 };
@@ -3564,6 +3569,10 @@ 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, SCDL)->size)
+		regs->scdl = sci_serial_in(port, SCDL);
+	if (sci_getreg(port, SCCKS)->size)
+		regs->sccks = sci_serial_in(port, SCCKS);
 	if (sci_getreg(port, SCSMR)->size)
 		regs->scsmr = sci_serial_in(port, SCSMR);
 	if (sci_getreg(port, SCSCR)->size)
@@ -3574,6 +3583,12 @@ static void sci_console_save(struct sci_port *s)
 		regs->scsptr = sci_serial_in(port, SCSPTR);
 	if (sci_getreg(port, SCBRR)->size)
 		regs->scbrr = sci_serial_in(port, SCBRR);
+	if (sci_getreg(port, HSSRR)->size)
+		regs->hssrr = sci_serial_in(port, HSSRR);
+	if (sci_getreg(port, SCPCR)->size)
+		regs->scpcr = sci_serial_in(port, SCPCR);
+	if (sci_getreg(port, SCPDR)->size)
+		regs->scpdr = sci_serial_in(port, SCPDR);
 	if (sci_getreg(port, SEMR)->size)
 		regs->semr = sci_serial_in(port, SEMR);
 }
@@ -3583,6 +3598,10 @@ 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, SCDL)->size)
+		sci_serial_out(port, SCDL, regs->scdl);
+	if (sci_getreg(port, SCCKS)->size)
+		sci_serial_out(port, SCCKS, regs->sccks);
 	if (sci_getreg(port, SCSMR)->size)
 		sci_serial_out(port, SCSMR, regs->scsmr);
 	if (sci_getreg(port, SCSCR)->size)
@@ -3593,6 +3612,12 @@ static void sci_console_restore(struct sci_port *s)
 		sci_serial_out(port, SCSPTR, regs->scsptr);
 	if (sci_getreg(port, SCBRR)->size)
 		sci_serial_out(port, SCBRR, regs->scbrr);
+	if (sci_getreg(port, HSSRR)->size)
+		sci_serial_out(port, HSSRR, regs->hssrr);
+	if (sci_getreg(port, SCPCR)->size)
+		sci_serial_out(port, SCPCR, regs->scpcr);
+	if (sci_getreg(port, SCPDR)->size)
+		sci_serial_out(port, SCPDR, regs->scpdr);
 	if (sci_getreg(port, SEMR)->size)
 		sci_serial_out(port, SEMR, regs->semr);
 }
-- 
2.39.5