1 files changed, 118 insertions, 43 deletions

diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c
index 9e2bbf5b4a8c..3d34cdc4a3a5 100644
--- a/drivers/pwm/pwm-imx27.c
+++ b/drivers/pwm/pwm-imx27.c
@@ -26,6 +26,7 @@
 #define MX3_PWMSR			0x04    /* PWM Status Register */
 #define MX3_PWMSAR			0x0C    /* PWM Sample Register */
 #define MX3_PWMPR			0x10    /* PWM Period Register */
+#define MX3_PWMCNR			0x14    /* PWM Counter Register */
 
 #define MX3_PWMCR_FWM			GENMASK(27, 26)
 #define MX3_PWMCR_STOPEN		BIT(25)
@@ -79,9 +80,12 @@
 /* PWMPR register value of 0xffff has the same effect as 0xfffe */
 #define MX3_PWMPR_MAX			0xfffe
 
+static const char * const pwm_imx27_clks[] = {"ipg", "per"};
+#define PWM_IMX27_PER			1
+
 struct pwm_imx27_chip {
-	struct clk	*clk_ipg;
-	struct clk	*clk_per;
+	struct clk_bulk_data clks[ARRAY_SIZE(pwm_imx27_clks)];
+	int clks_cnt;
 	void __iomem	*mmio_base;
 
 	/*
@@ -97,29 +101,6 @@ static inline struct pwm_imx27_chip *to_pwm_imx27_chip(struct pwm_chip *chip)
 	return pwmchip_get_drvdata(chip);
 }
 
-static int pwm_imx27_clk_prepare_enable(struct pwm_imx27_chip *imx)
-{
-	int ret;
-
-	ret = clk_prepare_enable(imx->clk_ipg);
-	if (ret)
-		return ret;
-
-	ret = clk_prepare_enable(imx->clk_per);
-	if (ret) {
-		clk_disable_unprepare(imx->clk_ipg);
-		return ret;
-	}
-
-	return 0;
-}
-
-static void pwm_imx27_clk_disable_unprepare(struct pwm_imx27_chip *imx)
-{
-	clk_disable_unprepare(imx->clk_per);
-	clk_disable_unprepare(imx->clk_ipg);
-}
-
 static int pwm_imx27_get_state(struct pwm_chip *chip,
 			       struct pwm_device *pwm, struct pwm_state *state)
 {
@@ -128,7 +109,7 @@ static int pwm_imx27_get_state(struct pwm_chip *chip,
 	u64 tmp;
 	int ret;
 
-	ret = pwm_imx27_clk_prepare_enable(imx);
+	ret = clk_bulk_prepare_enable(imx->clks_cnt, imx->clks);
 	if (ret < 0)
 		return ret;
 
@@ -151,7 +132,7 @@ static int pwm_imx27_get_state(struct pwm_chip *chip,
 	}
 
 	prescaler = MX3_PWMCR_PRESCALER_GET(val);
-	pwm_clk = clk_get_rate(imx->clk_per);
+	pwm_clk = clk_get_rate(imx->clks[PWM_IMX27_PER].clk);
 	val = readl(imx->mmio_base + MX3_PWMPR);
 	period = val >= MX3_PWMPR_MAX ? MX3_PWMPR_MAX : val;
 
@@ -171,7 +152,7 @@ static int pwm_imx27_get_state(struct pwm_chip *chip,
 	tmp = NSEC_PER_SEC * (u64)(val) * prescaler;
 	state->duty_cycle = DIV_ROUND_UP_ULL(tmp, pwm_clk);
 
-	pwm_imx27_clk_disable_unprepare(imx);
+	clk_bulk_disable_unprepare(imx->clks_cnt, imx->clks);
 
 	return 0;
 }
@@ -219,14 +200,16 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip,
 static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			   const struct pwm_state *state)
 {
-	unsigned long period_cycles, duty_cycles, prescale;
+	unsigned long period_cycles, duty_cycles, prescale, period_us, tmp;
 	struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
 	unsigned long long c;
 	unsigned long long clkrate;
+	unsigned long flags;
+	int val;
 	int ret;
 	u32 cr;
 
-	clkrate = clk_get_rate(imx->clk_per);
+	clkrate = clk_get_rate(imx->clks[PWM_IMX27_PER].clk);
 	c = clkrate * state->period;
 
 	do_div(c, NSEC_PER_SEC);
@@ -256,14 +239,105 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (pwm->state.enabled) {
 		pwm_imx27_wait_fifo_slot(chip, pwm);
 	} else {
-		ret = pwm_imx27_clk_prepare_enable(imx);
+		ret = clk_bulk_prepare_enable(imx->clks_cnt, imx->clks);
 		if (ret)
 			return ret;
 
 		pwm_imx27_sw_reset(chip);
 	}
 
-	writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
+	val = readl(imx->mmio_base + MX3_PWMPR);
+	val = val >= MX3_PWMPR_MAX ? MX3_PWMPR_MAX : val;
+	cr = readl(imx->mmio_base + MX3_PWMCR);
+	tmp = NSEC_PER_SEC * (u64)(val + 2) * MX3_PWMCR_PRESCALER_GET(cr);
+	tmp = DIV_ROUND_UP_ULL(tmp, clkrate);
+	period_us = DIV_ROUND_UP_ULL(tmp, 1000);
+
+	/*
+	 * ERR051198:
+	 * PWM: PWM output may not function correctly if the FIFO is empty when
+	 * a new SAR value is programmed
+	 *
+	 * Description:
+	 * When the PWM FIFO is empty, a new value programmed to the PWM Sample
+	 * register (PWM_PWMSAR) will be directly applied even if the current
+	 * timer period has not expired.
+	 *
+	 * If the new SAMPLE value programmed in the PWM_PWMSAR register is
+	 * less than the previous value, and the PWM counter register
+	 * (PWM_PWMCNR) that contains the current COUNT value is greater than
+	 * the new programmed SAMPLE value, the current period will not flip
+	 * the level. This may result in an output pulse with a duty cycle of
+	 * 100%.
+	 *
+	 * Consider a change from
+	 *     ________
+	 *    /        \______/
+	 *    ^      *        ^
+	 * to
+	 *     ____
+	 *    /    \__________/
+	 *    ^               ^
+	 * At the time marked by *, the new write value will be directly applied
+	 * to SAR even the current period is not over if FIFO is empty.
+	 *
+	 *     ________        ____________________
+	 *    /        \______/                    \__________/
+	 *    ^               ^      *        ^               ^
+	 *    |<-- old SAR -->|               |<-- new SAR -->|
+	 *
+	 * That is the output is active for a whole period.
+	 *
+	 * Workaround:
+	 * Check new SAR less than old SAR and current counter is in errata
+	 * windows, write extra old SAR into FIFO and new SAR will effect at
+	 * next period.
+	 *
+	 * Sometime period is quite long, such as over 1 second. If add old SAR
+	 * into FIFO unconditional, new SAR have to wait for next period. It
+	 * may be too long.
+	 *
+	 * Turn off the interrupt to ensure that not IRQ and schedule happen
+	 * during above operations. If any irq and schedule happen, counter
+	 * in PWM will be out of data and take wrong action.
+	 *
+	 * Add a safety margin 1.5us because it needs some time to complete
+	 * IO write.
+	 *
+	 * Use writel_relaxed() to minimize the interval between two writes to
+	 * the SAR register to increase the fastest PWM frequency supported.
+	 *
+	 * When the PWM period is longer than 2us(or <500kHz), this workaround
+	 * can solve this problem. No software workaround is available if PWM
+	 * period is shorter than IO write. Just try best to fill old data
+	 * into FIFO.
+	 */
+	c = clkrate * 1500;
+	do_div(c, NSEC_PER_SEC);
+
+	local_irq_save(flags);
+	val = FIELD_GET(MX3_PWMSR_FIFOAV, readl_relaxed(imx->mmio_base + MX3_PWMSR));
+
+	if (duty_cycles < imx->duty_cycle && (cr & MX3_PWMCR_EN)) {
+		if (period_us < 2) { /* 2us = 500 kHz */
+			/* Best effort attempt to fix up >500 kHz case */
+			udelay(3 * period_us);
+			writel_relaxed(imx->duty_cycle, imx->mmio_base + MX3_PWMSAR);
+			writel_relaxed(imx->duty_cycle, imx->mmio_base + MX3_PWMSAR);
+		} else if (val < MX3_PWMSR_FIFOAV_2WORDS) {
+			val = readl_relaxed(imx->mmio_base + MX3_PWMCNR);
+			/*
+			 * If counter is close to period, controller may roll over when
+			 * next IO write.
+			 */
+			if ((val + c >= duty_cycles && val < imx->duty_cycle) ||
+			    val + c >= period_cycles)
+				writel_relaxed(imx->duty_cycle, imx->mmio_base + MX3_PWMSAR);
+		}
+	}
+	writel_relaxed(duty_cycles, imx->mmio_base + MX3_PWMSAR);
+	local_irq_restore(flags);
+
 	writel(period_cycles, imx->mmio_base + MX3_PWMPR);
 
 	/*
@@ -287,7 +361,7 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	writel(cr, imx->mmio_base + MX3_PWMCR);
 
 	if (!state->enabled)
-		pwm_imx27_clk_disable_unprepare(imx);
+		clk_bulk_disable_unprepare(imx->clks_cnt, imx->clks);
 
 	return 0;
 }
@@ -309,21 +383,22 @@ static int pwm_imx27_probe(struct platform_device *pdev)
 	struct pwm_imx27_chip *imx;
 	int ret;
 	u32 pwmcr;
+	int i;
 
 	chip = devm_pwmchip_alloc(&pdev->dev, 1, sizeof(*imx));
 	if (IS_ERR(chip))
 		return PTR_ERR(chip);
 	imx = to_pwm_imx27_chip(chip);
 
-	imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
-	if (IS_ERR(imx->clk_ipg))
-		return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_ipg),
-				     "getting ipg clock failed\n");
+	imx->clks_cnt = ARRAY_SIZE(pwm_imx27_clks);
+	for (i = 0; i < imx->clks_cnt; ++i)
+		imx->clks[i].id = pwm_imx27_clks[i];
+
+	ret = devm_clk_bulk_get(&pdev->dev, imx->clks_cnt, imx->clks);
 
-	imx->clk_per = devm_clk_get(&pdev->dev, "per");
-	if (IS_ERR(imx->clk_per))
-		return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_per),
-				     "failed to get peripheral clock\n");
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret,
+				     "getting clocks failed\n");
 
 	chip->ops = &pwm_imx27_ops;
 
@@ -331,14 +406,14 @@ static int pwm_imx27_probe(struct platform_device *pdev)
 	if (IS_ERR(imx->mmio_base))
 		return PTR_ERR(imx->mmio_base);
 
-	ret = pwm_imx27_clk_prepare_enable(imx);
+	ret = clk_bulk_prepare_enable(imx->clks_cnt, imx->clks);
 	if (ret)
 		return ret;
 
 	/* keep clks on if pwm is running */
 	pwmcr = readl(imx->mmio_base + MX3_PWMCR);
 	if (!(pwmcr & MX3_PWMCR_EN))
-		pwm_imx27_clk_disable_unprepare(imx);
+		clk_bulk_disable_unprepare(imx->clks_cnt, imx->clks);
 
 	return devm_pwmchip_add(&pdev->dev, chip);
 }