linux-kernel - [PATCH v3 3/3] serial: 8250_of: manage bus clock in suspend/resume

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Message-ID: <20250411154419.1379529-4-elder@riscstar.com>
Date: Fri, 11 Apr 2025 10:44:18 -0500
From: Alex Elder <elder@...cstar.com>
To: gregkh@...uxfoundation.org,
	jirislaby@...nel.org,
	robh@...nel.org,
	krzk+dt@...nel.org,
	conor+dt@...nel.org
Cc: dlan@...too.org,
	benjamin.larsson@...exis.eu,
	bastien.curutchet@...tlin.com,
	andriy.shevchenko@...ux.intel.com,
	u.kleine-koenig@...libre.com,
	lkundrak@...sk,
	devicetree@...r.kernel.org,
	linux-serial@...r.kernel.org,
	spacemit@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 3/3] serial: 8250_of: manage bus clock in suspend/resume

Save the bus clock pointer in the of_serial_info structure, and use
that to disable the bus clock on suspend and re-enable it on resume.

Signed-off-by: Alex Elder <elder@...cstar.com>
---
v3: New patch, managing the bus clock during suspend and resume

 drivers/tty/serial/8250/8250_of.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
index a90a5462aa72a..8f2529f699e0a 100644
--- a/drivers/tty/serial/8250/8250_of.c
+++ b/drivers/tty/serial/8250/8250_of.c
@@ -24,6 +24,7 @@
 
 struct of_serial_info {
 	struct clk *clk;
+	struct clk *bus_clk;
 	struct reset_control *rst;
 	int type;
 	int line;
@@ -123,16 +124,15 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 
 	/* Get clk rate through clk driver if present */
 	if (!port->uartclk) {
-		struct clk *bus_clk;
-
-		bus_clk = devm_clk_get_optional_enabled(dev, "bus");
-		if (IS_ERR(bus_clk)) {
-			ret = dev_err_probe(dev, PTR_ERR(bus_clk), "failed to get bus clock\n");
+		info->bus_clk = devm_clk_get_optional_enabled(dev, "bus");
+		if (IS_ERR(info->bus_clk)) {
+			ret = dev_err_probe(dev, PTR_ERR(info->bus_clk),
+					    "failed to get bus clock\n");
 			goto err_pmruntime;
 		}
 
 		/* If the bus clock is required, core clock must be named */
-		info->clk = devm_clk_get_enabled(dev, bus_clk ? "core" : NULL);
+		info->clk = devm_clk_get_enabled(dev, info->bus_clk ? "core" : NULL);
 		if (IS_ERR(info->clk)) {
 			ret = dev_err_probe(dev, PTR_ERR(info->clk), "failed to get clock\n");
 			goto err_pmruntime;
@@ -299,6 +299,7 @@ static int of_serial_suspend(struct device *dev)
 	if (!uart_console(port) || console_suspend_enabled) {
 		pm_runtime_put_sync(dev);
 		clk_disable_unprepare(info->clk);
+		clk_disable_unprepare(info->bus_clk);
 	}
 	return 0;
 }
@@ -311,6 +312,7 @@ static int of_serial_resume(struct device *dev)
 
 	if (!uart_console(port) || console_suspend_enabled) {
 		pm_runtime_get_sync(dev);
+		clk_prepare_enable(info->bus_clk);
 		clk_prepare_enable(info->clk);
 	}
 
-- 
2.45.2