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Subject[PATCH 1/2] pwm: mtk-disp: Disable shadow registers before setting backlight values
Date
If shadow registers usage is not desired, disable that before performing
any write to CON0/1 registers in the .apply() callback, otherwise we may
lose clkdiv or period/width updates.

Fixes: cd4b45ac449a ("pwm: Add MediaTek MT2701 display PWM driver support")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
drivers/pwm/pwm-mtk-disp.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
index 692a06121b28..82b430d881a2 100644
--- a/drivers/pwm/pwm-mtk-disp.c
+++ b/drivers/pwm/pwm-mtk-disp.c
@@ -138,6 +138,19 @@ static int mtk_disp_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
high_width = mul_u64_u64_div_u64(state->duty_cycle, rate, div);
value = period | (high_width << PWM_HIGH_WIDTH_SHIFT);

+ if (mdp->data->bls_debug && !mdp->data->has_commit) {
+ /*
+ * For MT2701, disable double buffer before writing register
+ * and select manual mode and use PWM_PERIOD/PWM_HIGH_WIDTH.
+ */
+ mtk_disp_pwm_update_bits(mdp, mdp->data->bls_debug,
+ mdp->data->bls_debug_mask,
+ mdp->data->bls_debug_mask);
+ mtk_disp_pwm_update_bits(mdp, mdp->data->con0,
+ mdp->data->con0_sel,
+ mdp->data->con0_sel);
+ }
+
mtk_disp_pwm_update_bits(mdp, mdp->data->con0,
PWM_CLKDIV_MASK,
clk_div << PWM_CLKDIV_SHIFT);
@@ -152,17 +165,6 @@ static int mtk_disp_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
mtk_disp_pwm_update_bits(mdp, mdp->data->commit,
mdp->data->commit_mask,
0x0);
- } else {
- /*
- * For MT2701, disable double buffer before writing register
- * and select manual mode and use PWM_PERIOD/PWM_HIGH_WIDTH.
- */
- mtk_disp_pwm_update_bits(mdp, mdp->data->bls_debug,
- mdp->data->bls_debug_mask,
- mdp->data->bls_debug_mask);
- mtk_disp_pwm_update_bits(mdp, mdp->data->con0,
- mdp->data->con0_sel,
- mdp->data->con0_sel);
}

mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
--
2.39.0
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