[PATCH v4 2/6] clk: bcm: rpi: Add a comment about RPI_FIRMWARE_SET_CLOCK_STATE behavior

[Maíra Canal]

On some firmware versions, RPI_FIRMWARE_SET_CLOCK_STATE doesn't
actually power off the clock. Document this behavior so that clock
consumers understand they may need to set the rate to minimum before
disabling for meaningful power savings.

Suggested-by: Stefan Wahren <wahrenst at gmx.net>
Signed-off-by: Maíra Canal <mcanal at igalia.com>
---
 drivers/clk/bcm/clk-raspberrypi.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/clk/bcm/clk-raspberrypi.c b/drivers/clk/bcm/clk-raspberrypi.c
index 9783385d5859836898683209e320fcc928dfdc71..2e63121af0900ac9b4874b666cf6d02baa8be11c 100644
--- a/drivers/clk/bcm/clk-raspberrypi.c
+++ b/drivers/clk/bcm/clk-raspberrypi.c
@@ -308,6 +308,12 @@ static void raspberrypi_fw_unprepare(struct clk_hw *hw)
 	u32 state = 0;
 	int ret;
 
+	/*
+	 * On some firmware versions, RPI_FIRMWARE_SET_CLOCK_STATE doesn't
+	 * actually power off the clock. To achieve meaningful power consumption
+	 * reduction, consumers need to set the clock rate to minimum before
+	 * disabling it.
+	 */
 	ret = raspberrypi_clock_property(rpi->firmware, data,
 					 RPI_FIRMWARE_SET_CLOCK_STATE, &state);
 	if (ret)

-- 
2.52.0