diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c index e369b5a398f4..63aa9da92c22 100644 --- a/drivers/pwm/pwm-sun4i.c +++ b/drivers/pwm/pwm-sun4i.c @@ -3,6 +3,10 @@ * Driver for Allwinner sun4i Pulse Width Modulation Controller * * Copyright (C) 2014 Alexandre Belloni + * + * Limitations: + * - When outputing the source clock directly, the PWM logic will be bypassed + * and the currently running period is not guaranteed to be completed */ #include @@ -73,6 +77,7 @@ static const u32 prescaler_table[] = { struct sun4i_pwm_data { bool has_prescaler_bypass; + bool has_direct_mod_clk_output; unsigned int npwm; }; @@ -118,6 +123,20 @@ static void sun4i_pwm_get_state(struct pwm_chip *chip, val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG); + /* + * PWM chapter in H6 manual has a diagram which explains that if bypass + * bit is set, no other setting has any meaning. Even more, experiment + * proved that also enable bit is ignored in this case. + */ + if ((val & BIT_CH(PWM_BYPASS, pwm->hwpwm)) && + sun4i_pwm->data->has_direct_mod_clk_output) { + state->period = DIV_ROUND_UP_ULL(NSEC_PER_SEC, clk_rate); + state->duty_cycle = DIV_ROUND_UP_ULL(state->period, 2); + state->polarity = PWM_POLARITY_NORMAL; + state->enabled = true; + return; + } + if ((PWM_REG_PRESCAL(val, pwm->hwpwm) == PWM_PRESCAL_MASK) && sun4i_pwm->data->has_prescaler_bypass) prescaler = 1; @@ -149,13 +168,24 @@ static void sun4i_pwm_get_state(struct pwm_chip *chip, static int sun4i_pwm_calculate(struct sun4i_pwm_chip *sun4i_pwm, const struct pwm_state *state, - u32 *dty, u32 *prd, unsigned int *prsclr) + u32 *dty, u32 *prd, unsigned int *prsclr, + bool *bypass) { u64 clk_rate, div = 0; unsigned int pval, prescaler = 0; clk_rate = clk_get_rate(sun4i_pwm->clk); + *bypass = sun4i_pwm->data->has_direct_mod_clk_output && + state->enabled && + (state->period * clk_rate >= NSEC_PER_SEC) && + (state->period * clk_rate < 2 * NSEC_PER_SEC) && + (state->duty_cycle * clk_rate * 2 >= NSEC_PER_SEC); + + /* Skip calculation of other parameters if we bypass them */ + if (*bypass) + return 0; + if (sun4i_pwm->data->has_prescaler_bypass) { /* First, test without any prescaler when available */ prescaler = PWM_PRESCAL_MASK; @@ -206,6 +236,7 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, int ret; unsigned int delay_us, prescaler; unsigned long now; + bool bypass; pwm_get_state(pwm, &cstate); @@ -220,7 +251,8 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, spin_lock(&sun4i_pwm->ctrl_lock); ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG); - ret = sun4i_pwm_calculate(sun4i_pwm, state, &duty, &period, &prescaler); + ret = sun4i_pwm_calculate(sun4i_pwm, state, &duty, &period, &prescaler, + &bypass); if (ret) { dev_err(chip->dev, "period exceeds the maximum value\n"); spin_unlock(&sun4i_pwm->ctrl_lock); @@ -229,6 +261,18 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, return ret; } + if (sun4i_pwm->data->has_direct_mod_clk_output) { + if (bypass) { + ctrl |= BIT_CH(PWM_BYPASS, pwm->hwpwm); + /* We can skip other parameter */ + sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG); + spin_unlock(&sun4i_pwm->ctrl_lock); + return 0; + } + + ctrl &= ~BIT_CH(PWM_BYPASS, pwm->hwpwm); + } + if (PWM_REG_PRESCAL(ctrl, pwm->hwpwm) != prescaler) { /* Prescaler changed, the clock has to be gated */ ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);