clk: qcom: reset: Ensure write completion on reset de/assertion

Trying to toggle the resets in a rapid fashion can lead to the changes
not actually arriving at the clock controller block when we expect them
to. This was observed at least on SM8250.

Read back the value after regmap_update_bits to ensure write completion.

Fixes: b36ba30c8ac6 ("clk: qcom: Add reset controller support")
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20240105-topic-venus_reset-v2-3-c37eba13b5ce@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

diff --git a/drivers/clk/qcom/reset.c b/drivers/clk/qcom/reset.c
index 20d1d35aaf2294190a09cc86307e1b8c6418e6e3..d96c96a9089f40b3a111067434d4d19632505a16 100644 (file)
--- a/drivers/clk/qcom/reset.c
+++ b/drivers/clk/qcom/reset.c
@@ -33,7 +33,12 @@ static int qcom_reset_set_assert(struct reset_controller_dev *rcdev,
        map = &rst->reset_map[id];
        mask = map->bitmask ? map->bitmask : BIT(map->bit);
 
-       return regmap_update_bits(rst->regmap, map->reg, mask, assert ? mask : 0);
+       regmap_update_bits(rst->regmap, map->reg, mask, assert ? mask : 0);
+
+       /* Read back the register to ensure write completion, ignore the value */
+       regmap_read(rst->regmap, map->reg, &mask);
+
+       return 0;
 }
 
 static int qcom_reset_assert(struct reset_controller_dev *rcdev, unsigned long id)