[PATCH] clocksource/drivers/timer-mediatek: initialize GPT6 as system counter

[Roman Vivchar via B4 Relay <devnull+rva333.protonmail.com@kernel.org>]

From: Roman Vivchar <rva333@protonmail.com>

On certain MediaTek SoCs like mt6572 (likely before the CPUXGPT was
introduced), the generic arch timer is fed by the GPT6. Some bootloaders
don't initialize it properly, leading to dead arch timer.

Fix this by configuring GPT6 when the MediaTek timer is probed. This
makes arch timer work properly and removes IPI overhead from MediaTek
timer broadcast when arch timer is used.

If the timer was configured by the bootloader, this change is no-op.

Tested-by: Akari Tsuyukusa <akkun11.open@gmail.com> # MT6589
Signed-off-by: Roman Vivchar <rva333@protonmail.com>
---
On certain MediaTek SoCs like mt6572 (likely before the CPUXGPT was
introduced), the generic arch timer is fed by the GPT6. Some bootloaders
don't initialize it properly, leading to dead arch timer.

Fix this by configuring GPT6 when the MediaTek timer is probed. This
makes arch timer work properly and removes IPI overhead from MediaTek
timer broadcast when arch timer is used.

If the timer was configured by the bootloader, this change is no-op.
---
 drivers/clocksource/timer-mediatek.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/clocksource/timer-mediatek.c b/drivers/clocksource/timer-mediatek.c
index 7bcb4a3f26fb..7de34cace572 100644
--- a/drivers/clocksource/timer-mediatek.c
+++ b/drivers/clocksource/timer-mediatek.c
@@ -22,6 +22,8 @@
 
 #define TIMER_SYNC_TICKS        (3)
 
+#define TIMER_SYSCNT            (6)
+
 /* gpt */
 #define GPT_IRQ_EN_REG          0x00
 #define GPT_IRQ_ENABLE(val)     BIT((val) - 1)
@@ -335,6 +337,9 @@ static int __init mtk_gpt_init(struct device_node *node)
 
 	mtk_gpt_enable_irq(&to, TIMER_CLK_EVT);
 
+	/* Configure GPT6 to feed arch timer */
+	mtk_gpt_setup(&to, TIMER_SYSCNT, GPT_CTRL_OP_FREERUN);
+
 	return 0;
 }
 TIMER_OF_DECLARE(mtk_mt6577, "mediatek,mt6577-timer", mtk_gpt_init);

---
base-commit: 05f7e89ab9731565d8a62e3b5d1ec206485eeb0b
change-id: 20260325-archtimer-357b02f74058

Best regards,
-- 
Roman Vivchar <rva333@protonmail.com>