pwm: atmel-hlcdc: add at91sam9x5 and sama5d3 errata handling

at91sam9x5 has an errata forbidding the use of slow clk as a clk source and
sama5d3 SoCs has another errata forbidding the use of div1 prescaler.

Take both of these erratas into account.
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-atmel-hlcdc.c

@@ -32,10 +32,16 @@
 #define ATMEL_HLCDC_PWMPS_MAX		0x6
 #define ATMEL_HLCDC_PWMPS(x)		((x) & ATMEL_HLCDC_PWMPS_MASK)
 
+struct atmel_hlcdc_pwm_errata {
+	bool slow_clk_erratum;
+	bool div1_clk_erratum;
+};
+
 struct atmel_hlcdc_pwm {
 	struct pwm_chip chip;
 	struct atmel_hlcdc *hlcdc;
 	struct clk *cur_clk;
+	const struct atmel_hlcdc_pwm_errata *errata;
 };
 
 static inline struct atmel_hlcdc_pwm *to_atmel_hlcdc_pwm(struct pwm_chip *chip)
@@ -56,20 +62,29 @@ static int atmel_hlcdc_pwm_config(struct pwm_chip *c,
 	u32 pwmcfg;
 	int pres;
 
-	clk_freq = clk_get_rate(new_clk);
-	clk_period_ns = (u64)NSEC_PER_SEC * 256;
-	do_div(clk_period_ns, clk_freq);
+	if (!chip->errata || !chip->errata->slow_clk_erratum) {
+		clk_freq = clk_get_rate(new_clk);
+		clk_period_ns = (u64)NSEC_PER_SEC * 256;
+		do_div(clk_period_ns, clk_freq);
+	}
 
-	if (clk_period_ns > period_ns) {
+	/* Errata: cannot use slow clk on some IP revisions */
+	if ((chip->errata && chip->errata->slow_clk_erratum) ||
+	    clk_period_ns > period_ns) {
 		new_clk = hlcdc->sys_clk;
 		clk_freq = clk_get_rate(new_clk);
 		clk_period_ns = (u64)NSEC_PER_SEC * 256;
 		do_div(clk_period_ns, clk_freq);
 	}
 
-	for (pres = 0; pres <= ATMEL_HLCDC_PWMPS_MAX; pres++)
+	for (pres = 0; pres <= ATMEL_HLCDC_PWMPS_MAX; pres++) {
+		/* Errata: cannot divide by 1 on some IP revisions */
+		if (!pres && chip->errata && chip->errata->div1_clk_erratum)
+			continue;
+
 		if ((clk_period_ns << pres) >= period_ns)
 			break;
+	}
 
 	if (pres > ATMEL_HLCDC_PWMPS_MAX)
 		return -EINVAL;
@@ -187,8 +202,29 @@ static const struct pwm_ops atmel_hlcdc_pwm_ops = {
 	.owner = THIS_MODULE,
 };
 
+static const struct atmel_hlcdc_pwm_errata atmel_hlcdc_pwm_at91sam9x5_errata = {
+	.slow_clk_erratum = true,
+};
+
+static const struct atmel_hlcdc_pwm_errata atmel_hlcdc_pwm_sama5d3_errata = {
+	.div1_clk_erratum = true,
+};
+
+static const struct of_device_id atmel_hlcdc_dt_ids[] = {
+	{
+		.compatible = "atmel,at91sam9x5-hlcdc",
+		.data = &atmel_hlcdc_pwm_at91sam9x5_errata,
+	},
+	{
+		.compatible = "atmel,sama5d3-hlcdc",
+		.data = &atmel_hlcdc_pwm_sama5d3_errata,
+	},
+	{ /* sentinel */ },
+};
+
 static int atmel_hlcdc_pwm_probe(struct platform_device *pdev)
 {
+	const struct of_device_id *match;
 	struct device *dev = &pdev->dev;
 	struct atmel_hlcdc_pwm *chip;
 	struct atmel_hlcdc *hlcdc;
@@ -204,6 +240,10 @@ static int atmel_hlcdc_pwm_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	match = of_match_node(atmel_hlcdc_dt_ids, dev->parent->of_node);
+	if (match)
+		chip->errata = match->data;
+
 	chip->hlcdc = hlcdc;
 	chip->chip.ops = &atmel_hlcdc_pwm_ops;
 	chip->chip.dev = dev;