Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 82f64cd2 authored by Wolfram Sang's avatar Wolfram Sang Committed by Wim Van Sebroeck
Browse files

watchdog: renesas_wdt: apply better precision 



The error margin of the clks_per_second variable was too large and
caused offsets when used with clock frequencies which left a remainder
after applying the dividers. Now we always calculate directly using the
clock rate and the divider using some helper macros. That also means
that DIV_ROUND_UP moves from probe to the multiplication macro. In
probe, we don't need to ensure anymore that 'clks_per_sec' would go too
fast but rather ensure that the lower limit is really at least 1 to
certainly get a full cycle.

Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarWim Van Sebroeck <wim@iguana.be>
parent 1c1b2434

drivers/watchdog/renesas_wdt.c

+19 −9
Original line number Original line Diff line number Diff line
@@ -26,6 +26,17 @@ 




#define RWDT_DEFAULT_TIMEOUT 60U

#define RWDT_DEFAULT_TIMEOUT 60U





/*

 * In probe, clk_rate is checked to be not more than 16 bit * biggest clock

 * divider (10 bits). d is only a factor to fully utilize the WDT counter and

 * will not exceed its 16 bits. Thus, no overflow, we stay below 32 bits.

 */

#define MUL_BY_CLKS_PER_SEC(p, d) \

	DIV_ROUND_UP((d) * (p)->clk_rate, clk_divs[(p)->cks])



/* d is 16 bit, clk_divs 10 bit -> no 32 bit overflow */

#define DIV_BY_CLKS_PER_SEC(p, d) ((d) * clk_divs[(p)->cks] / (p)->clk_rate)



static const unsigned int clk_divs[] = { 1, 4, 16, 32, 64, 128, 1024 };

static const unsigned int clk_divs[] = { 1, 4, 16, 32, 64, 128, 1024 };





static bool nowayout = WATCHDOG_NOWAYOUT;

static bool nowayout = WATCHDOG_NOWAYOUT;
@@ -37,7 +48,7 @@ struct rwdt_priv { 
	void __iomem *base;

	void __iomem *base;

	struct watchdog_device wdev;

	struct watchdog_device wdev;

	struct clk *clk;

	struct clk *clk;

	unsigned long clks_per_sec;

	unsigned long clk_rate;

	u8 cks;

	u8 cks;

};

};
@@ -55,7 +66,7 @@ static int rwdt_init_timeout(struct watchdog_device *wdev) 
{

{

	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);

	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);





	rwdt_write(priv, 65536 - wdev->timeout * priv->clks_per_sec, RWTCNT);

	rwdt_write(priv, 65536 - MUL_BY_CLKS_PER_SEC(priv, wdev->timeout), RWTCNT);





	return 0;

	return 0;

}

}
@@ -92,7 +103,7 @@ static unsigned int rwdt_get_timeleft(struct watchdog_device *wdev) 
	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);

	struct rwdt_priv *priv = watchdog_get_drvdata(wdev);

	u16 val = readw_relaxed(priv->base + RWTCNT);

	u16 val = readw_relaxed(priv->base + RWTCNT);





	return (65536 - val) / priv->clks_per_sec;

	return DIV_BY_CLKS_PER_SEC(priv, 65536 - val);

}

}





static const struct watchdog_info rwdt_ident = {

static const struct watchdog_info rwdt_ident = {
@@ -112,7 +123,7 @@ static int rwdt_probe(struct platform_device *pdev) 
{

{

	struct rwdt_priv *priv;

	struct rwdt_priv *priv;

	struct resource *res;

	struct resource *res;

	unsigned long rate, clks_per_sec;

	unsigned long clks_per_sec;

	int ret, i;

	int ret, i;





	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);

	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
@@ -128,14 +139,13 @@ static int rwdt_probe(struct platform_device *pdev) 
	if (IS_ERR(priv->clk))

	if (IS_ERR(priv->clk))

		return PTR_ERR(priv->clk);

		return PTR_ERR(priv->clk);





	rate = clk_get_rate(priv->clk);

	priv->clk_rate = clk_get_rate(priv->clk);

	if (!rate)

	if (!priv->clk_rate)

		return -ENOENT;

		return -ENOENT;





	for (i = ARRAY_SIZE(clk_divs) - 1; i >= 0; i--) {

	for (i = ARRAY_SIZE(clk_divs) - 1; i >= 0; i--) {

		clks_per_sec = DIV_ROUND_UP(rate, clk_divs[i]);

		clks_per_sec = priv->clk_rate / clk_divs[i];

		if (clks_per_sec && clks_per_sec < 65536) {

		if (clks_per_sec && clks_per_sec < 65536) {

			priv->clks_per_sec = clks_per_sec;

			priv->cks = i;

			priv->cks = i;

			break;

			break;

		}

		}
@@ -153,7 +163,7 @@ static int rwdt_probe(struct platform_device *pdev) 
	priv->wdev.ops = &rwdt_ops,

	priv->wdev.ops = &rwdt_ops,

	priv->wdev.parent = &pdev->dev;

	priv->wdev.parent = &pdev->dev;

	priv->wdev.min_timeout = 1;

	priv->wdev.min_timeout = 1;

	priv->wdev.max_timeout = 65536 / clks_per_sec;

	priv->wdev.max_timeout = DIV_BY_CLKS_PER_SEC(priv, 65536);

	priv->wdev.timeout = min(priv->wdev.max_timeout, RWDT_DEFAULT_TIMEOUT);

	priv->wdev.timeout = min(priv->wdev.max_timeout, RWDT_DEFAULT_TIMEOUT);





	platform_set_drvdata(pdev, priv);

	platform_set_drvdata(pdev, priv);