[][kernel][mt7988][pwm][add longer pwm period support]
[Description]
Add longer pwm period support for mediatek PWM, this make customer
able to blink LED via PWM pins.
[Release-log]
N/A
Change-Id: I75f566240ce6f0d8d9729de998f07e2bcba378d4
Change-Id: I30a738d053bc875c6c6ff9cb415d2b3c37441d4a
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6705185
diff --git a/target/linux/mediatek/patches-5.4/0950-pwm-mediatek-add-longer-period-support.patch b/target/linux/mediatek/patches-5.4/0950-pwm-mediatek-add-longer-period-support.patch
new file mode 100644
index 0000000..0934ae2
--- /dev/null
+++ b/target/linux/mediatek/patches-5.4/0950-pwm-mediatek-add-longer-period-support.patch
@@ -0,0 +1,65 @@
+diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
+index 9701092..79d15a9 100644
+--- a/drivers/pwm/pwm-mediatek.c
++++ b/drivers/pwm/pwm-mediatek.c
+@@ -152,8 +152,11 @@ static int pwm_mediatek_config(struct pwm_chip *chip, struct pwm_device *pwm,
+ int duty_ns, int period_ns)
+ {
+ struct pwm_mediatek_chip *pc = to_pwm_mediatek_chip(chip);
+- u32 clkdiv = 0, cnt_period, cnt_duty, reg_width = PWMDWIDTH,
+- reg_thres = PWMTHRES;
++ /* The source clock is divided by 2^clkdiv or iff the clksel bit
++ * is set by (2^clkdiv*1625)
++ */
++ u32 clkdiv = 0, clksel = 0, cnt_period, cnt_duty,
++ reg_width = PWMDWIDTH, reg_thres = PWMTHRES;
+ u64 resolution;
+ int ret;
+
+@@ -164,12 +167,30 @@ static int pwm_mediatek_config(struct pwm_chip *chip, struct pwm_device *pwm,
+
+ /* Using resolution in picosecond gets accuracy higher */
+ resolution = (u64)NSEC_PER_SEC * 1000;
++ /* Calculate resolution based on current clock frequency */
+ do_div(resolution, clk_get_rate(pc->clk_pwms[pwm->hwpwm]));
+-
++ /* Using resolution to calculate cnt_period which represents
++ * the effective range of the PWM period counter
++ */
+ cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000, resolution);
+ while (cnt_period > 8191) {
++ /* Using clkdiv to reduce clock frequency and calculate
++ * new resolution based on new clock speed
++ */
+ resolution *= 2;
+ clkdiv++;
++ if (clkdiv > PWM_CLK_DIV_MAX && !clksel) {
++ /* Using clksel to divide the pwm source clock by
++ * an additional 1625, and recalculate new clkdiv
++ * and resolution
++ */
++ clksel = 1;
++ clkdiv = 0;
++ resolution = (u64)NSEC_PER_SEC * 1000 * 1625;
++ do_div(resolution,
++ clk_get_rate(pc->clk_pwms[pwm->hwpwm]));
++ }
++ /* Calculate cnt_period based on resolution */
+ cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000,
+ resolution);
+ }
+@@ -189,8 +210,13 @@ static int pwm_mediatek_config(struct pwm_chip *chip, struct pwm_device *pwm,
+ reg_thres = PWM45THRES_FIXUP;
+ }
+
++ /* Calculate cnt_duty based on resolution */
+ cnt_duty = DIV_ROUND_CLOSEST_ULL((u64)duty_ns * 1000, resolution);
+- pwm_mediatek_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | clkdiv);
++ if (clksel)
++ pwm_mediatek_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | BIT(3) |
++ clkdiv);
++ else
++ pwm_mediatek_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | clkdiv);
+ pwm_mediatek_writel(pc, pwm->hwpwm, reg_width, cnt_period);
+ pwm_mediatek_writel(pc, pwm->hwpwm, reg_thres, cnt_duty);
+