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serial: 8250_mtk: Enable baud clock and manage in runtime PM

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Some MediaTek SoCs got a gated UART baud clock, which currently gets
disabled as the clk subsystem believes it would be unused. This results in
the uart freezing right after "clk: Disabling unused clocks" on those
platforms.

Request the baud clock to be prepared and enabled during probe, and to
restore run-time power management capabilities to what it was before commit
e32a83c70c ("serial: 8250-mtk: modify mtk uart power and clock
management") disable and unprepare the baud clock when suspending the UART,
prepare and enable it again when resuming it.

Fixes: e32a83c70c ("serial: 8250-mtk: modify mtk uart power and clock management")
Fixes: b6c7ff2693 ("serial: 8250_mtk: Simplify clock sequencing and runtime PM")
Cc: stable <stable@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/de5197ccc31e1dab0965cabcc11ca92e67246cf6.1758058441.git.daniel@makrotopia.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Golle
2025-09-16 22:37:27 +01:00
committed by Greg Kroah-Hartman
parent daeb4037ad
commit d518314a1f
1 changed files with 4 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/tty/serial/8250/8250_mtk.c
+4 -2
View File
@@ -435,6 +435,7 @@ static int __maybe_unused mtk8250_runtime_suspend(struct device *dev)
while
(serial_in(up, MTK_UART_DEBUG0));
clk_disable_unprepare(data->uart_clk);
clk_disable_unprepare(data->bus_clk);
return 0;
@@ -445,6 +446,7 @@ static int __maybe_unused mtk8250_runtime_resume(struct device *dev)
struct mtk8250_data *data = dev_get_drvdata(dev);
clk_prepare_enable(data->bus_clk);
clk_prepare_enable(data->uart_clk);
return 0;
}
@@ -475,13 +477,13 @@ static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
int dmacnt;
#endif
data->uart_clk = devm_clk_get(&pdev->dev, "baud");
data->uart_clk = devm_clk_get_enabled(&pdev->dev, "baud");
if (IS_ERR(data->uart_clk)) {
/*
* For compatibility with older device trees try unnamed
* clk when no baud clk can be found.
*/
data->uart_clk = devm_clk_get(&pdev->dev, NULL);
data->uart_clk = devm_clk_get_enabled(&pdev->dev, NULL);
if (IS_ERR(data->uart_clk)) {
dev_warn(&pdev->dev, "Can't get uart clock\n");
return PTR_ERR(data->uart_clk);