pwm: mtk-disp: Disable shadow registers before setting backlight values

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>
Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Tested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Tested-by: Alexandre Mergnat <amergnat@baylibre.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
index 4cfe88d..ea36197 100644 (file)
--- 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,