From cd378881426379a62a7fe67f34b8cbe738302022 Mon Sep 17 00:00:00 2001 From: David Rivshin Date: Fri, 29 Jan 2016 23:26:52 -0500 Subject: pwm: omap-dmtimer: Add sanity checking for load and match values Add sanity checking to ensure that we do not program load or match values that are out of range if a user requests period or duty_cycle values which are not achievable. The match value cannot be less than the load value (but can be equal), and neither can be 0xffffffff. This means that there must be at least one fclk cycle between load and match, and another between match and overflow. Fixes: 6604c6556db9 ("pwm: Add PWM driver for OMAP using dual-mode timers") Signed-off-by: David Rivshin Acked-by: Neil Armstrong [thierry.reding@gmail.com: minor coding style cleanups] Signed-off-by: Thierry Reding --- drivers/pwm/pwm-omap-dmtimer.c | 34 ++++++++++++++++++++++++++++++---- 1 file changed, 30 insertions(+), 4 deletions(-) (limited to 'drivers/pwm/pwm-omap-dmtimer.c') diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c index 0083e75d950f..54641e45f45b 100644 --- a/drivers/pwm/pwm-omap-dmtimer.c +++ b/drivers/pwm/pwm-omap-dmtimer.c @@ -119,15 +119,13 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip, fclk = omap->pdata->get_fclk(omap->dm_timer); if (!fclk) { dev_err(chip->dev, "invalid pmtimer fclk\n"); - mutex_unlock(&omap->mutex); - return -EINVAL; + goto err_einval; } clk_rate = clk_get_rate(fclk); if (!clk_rate) { dev_err(chip->dev, "invalid pmtimer fclk rate\n"); - mutex_unlock(&omap->mutex); - return -EINVAL; + goto err_einval; } dev_dbg(chip->dev, "clk rate: %luHz\n", clk_rate); @@ -142,6 +140,8 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip, * The non-active time is the remainder: (DM_TIMER_MAX-match_value) * clock cycles. * + * NOTE: It is required that: load_value <= match_value < DM_TIMER_MAX + * * References: * OMAP4430/60/70 TRM sections 22.2.4.10 and 22.2.4.11 * AM335x Sitara TRM sections 20.1.3.5 and 20.1.3.6 @@ -149,6 +149,27 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip, period_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, period_ns); duty_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, duty_ns); + if (period_cycles < 2) { + dev_info(chip->dev, + "period %d ns too short for clock rate %lu Hz\n", + period_ns, clk_rate); + goto err_einval; + } + + if (duty_cycles < 1) { + dev_dbg(chip->dev, + "duty cycle %d ns is too short for clock rate %lu Hz\n", + duty_ns, clk_rate); + dev_dbg(chip->dev, "using minimum of 1 clock cycle\n"); + duty_cycles = 1; + } else if (duty_cycles >= period_cycles) { + dev_dbg(chip->dev, + "duty cycle %d ns is too long for period %d ns at clock rate %lu Hz\n", + duty_ns, period_ns, clk_rate); + dev_dbg(chip->dev, "using maximum of 1 clock cycle less than period\n"); + duty_cycles = period_cycles - 1; + } + load_value = (DM_TIMER_MAX - period_cycles) + 1; match_value = load_value + duty_cycles - 1; @@ -179,6 +200,11 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip, mutex_unlock(&omap->mutex); return 0; + +err_einval: + mutex_unlock(&omap->mutex); + + return -EINVAL; } static int pwm_omap_dmtimer_set_polarity(struct pwm_chip *chip, -- cgit v1.2.3-59-g8ed1b