[PATCH v2 0/4] watchdog: cadence_wdt: Support all available prescaler values

[PATCH v2 0/4] watchdog: cadence_wdt: Support all available prescaler values

[Melin Tomas]

Cadence watchdog HW supports prescaler values of 8, 64, 512 and 4096,
currently only 512 and 4096 are used by driver.

This series adds support to select prescaler values of 8 and 64 for
lower input clock frequencies.

Changes v2:

- Add calculation of actual min/max timeout values
- Validate input clock frequencies to not allow
  frequencies that would result in timeout granularity
  of > 1 second.

Tomas Melin (4):
  watchdog: cadence_wdt: Move clock detection eariler in probe
  watchdog: cadence_wdt: Calculate actual timeout limits
  watchdog: cadence_wdt: Group struct member init statements
  watchdog: cadence_wdt: Support all available prescaler values

 drivers/watchdog/cadence_wdt.c | 65 ++++++++++++++++++++--------------
 1 file changed, 38 insertions(+), 27 deletions(-)

-- 
2.17.2

[PATCH v2 1/4] watchdog: cadence_wdt: Move clock detection eariler in probe

[Melin Tomas]

Timeout calculation needs clock frequency, so init clock and calculate
prescaler value eariler in the probe.

Preparational step for calculating maximum and minimum timeout values
for driver.

Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
---
 drivers/watchdog/cadence_wdt.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
index c3924356d173..415bd6dd1edb 100644
--- a/drivers/watchdog/cadence_wdt.c
+++ b/drivers/watchdog/cadence_wdt.c
@@ -295,6 +295,22 @@ static int cdns_wdt_probe(struct platform_device *pdev)
 	if (!wdt)
 		return -ENOMEM;
 
+	wdt->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(wdt->clk)) {
+		dev_err(&pdev->dev, "input clock not found\n");
+		ret = PTR_ERR(wdt->clk);
+		return ret;
+	}
+
+	clock_f = clk_get_rate(wdt->clk);
+	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
+		wdt->prescaler = CDNS_WDT_PRESCALE_512;
+		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
+	} else {
+		wdt->prescaler = CDNS_WDT_PRESCALE_4096;
+		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
+	}
+
 	cdns_wdt_device = &wdt->cdns_wdt_device;
 	cdns_wdt_device->info = &cdns_wdt_info;
 	cdns_wdt_device->ops = &cdns_wdt_ops;
@@ -334,28 +350,12 @@ static int cdns_wdt_probe(struct platform_device *pdev)
 	watchdog_stop_on_reboot(cdns_wdt_device);
 	watchdog_set_drvdata(cdns_wdt_device, wdt);
 
-	wdt->clk = devm_clk_get(&pdev->dev, NULL);
-	if (IS_ERR(wdt->clk)) {
-		dev_err(&pdev->dev, "input clock not found\n");
-		ret = PTR_ERR(wdt->clk);
-		return ret;
-	}
-
 	ret = clk_prepare_enable(wdt->clk);
 	if (ret) {
 		dev_err(&pdev->dev, "unable to enable clock\n");
 		return ret;
 	}
 
-	clock_f = clk_get_rate(wdt->clk);
-	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
-		wdt->prescaler = CDNS_WDT_PRESCALE_512;
-		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
-	} else {
-		wdt->prescaler = CDNS_WDT_PRESCALE_4096;
-		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
-	}
-
 	spin_lock_init(&wdt->io_lock);
 
 	ret = watchdog_register_device(cdns_wdt_device);
-- 
2.17.2

[PATCH v2 2/4] watchdog: cadence_wdt: Calculate actual timeout limits

[Melin Tomas]

Maximum and minimum timeout values depend on the actual input clock
frequency and prescaler selection.

Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
---
 drivers/watchdog/cadence_wdt.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
index 415bd6dd1edb..87b767c87bb6 100644
--- a/drivers/watchdog/cadence_wdt.c
+++ b/drivers/watchdog/cadence_wdt.c
@@ -18,9 +18,6 @@
 #include <linux/watchdog.h>
 
 #define CDNS_WDT_DEFAULT_TIMEOUT	10
-/* Supports 1 - 516 sec */
-#define CDNS_WDT_MIN_TIMEOUT	1
-#define CDNS_WDT_MAX_TIMEOUT	516
 
 /* Restart key */
 #define CDNS_WDT_RESTART_KEY 0x00001999
@@ -28,6 +25,10 @@
 /* Counter register access key */
 #define CDNS_WDT_REGISTER_ACCESS_KEY 0x00920000
 
+/* Counter control register, counter restart values */
+#define CDNS_WDT_CCR_CRV_MIN 0xFFF
+#define CDNS_WDT_CCR_CRV_MAX 0xFFFFFF
+
 /* Counter value divisor */
 #define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000
 
@@ -315,8 +316,10 @@ static int cdns_wdt_probe(struct platform_device *pdev)
 	cdns_wdt_device->info = &cdns_wdt_info;
 	cdns_wdt_device->ops = &cdns_wdt_ops;
 	cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
-	cdns_wdt_device->min_timeout = CDNS_WDT_MIN_TIMEOUT;
-	cdns_wdt_device->max_timeout = CDNS_WDT_MAX_TIMEOUT;
+	cdns_wdt_device->min_timeout =
+		CDNS_WDT_CCR_CRV_MIN * wdt->prescaler / clock_f;
+	cdns_wdt_device->max_timeout =
+		CDNS_WDT_CCR_CRV_MAX * wdt->prescaler / clock_f;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	wdt->regs = devm_ioremap_resource(&pdev->dev, res);
-- 
2.17.2

[PATCH v2 3/4] watchdog: cadence_wdt: Group struct member init statements

[Melin Tomas]

Move init statement and remove stray comment.

Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
---
 drivers/watchdog/cadence_wdt.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
index 87b767c87bb6..4657800d9d8e 100644
--- a/drivers/watchdog/cadence_wdt.c
+++ b/drivers/watchdog/cadence_wdt.c
@@ -313,6 +313,7 @@ static int cdns_wdt_probe(struct platform_device *pdev)
 	}
 	
 	cdns_wdt_device = &wdt->cdns_wdt_device;
+	cdns_wdt_device->parent = &pdev->dev;
 	cdns_wdt_device->info = &cdns_wdt_info;
 	cdns_wdt_device->ops = &cdns_wdt_ops;
 	cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
@@ -340,9 +341,6 @@ static int cdns_wdt_probe(struct platform_device *pdev)
 		}
 	}
 
-	/* Initialize the members of cdns_wdt structure */
-	cdns_wdt_device->parent = &pdev->dev;
-
 	ret = watchdog_init_timeout(cdns_wdt_device, wdt_timeout, &pdev->dev);
 	if (ret) {
 		dev_err(&pdev->dev, "unable to set timeout value\n");
-- 
2.17.2

[PATCH v2 4/4] watchdog: cadence_wdt: Support all available prescaler values

[Melin Tomas]

Cadence watchdog HW supports prescaler values of
8, 64, 512 and 4096.

Add support to select prescaler values of 8 and 64 for lower
input clock frequencies.

Prescaler value is selected to keep timeout resolution of 1 second.
For clock frequencies below 32kHz, 1 second resolution does
no longer hold, thereby returning an error.

Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
---
 drivers/watchdog/cadence_wdt.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
index 4657800d9d8e..39109b5721c1 100644
--- a/drivers/watchdog/cadence_wdt.c
+++ b/drivers/watchdog/cadence_wdt.c
@@ -33,16 +33,17 @@
 #define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000
 
 /* Clock prescaler value and selection */
+#define CDNS_WDT_PRESCALE_8	8
 #define CDNS_WDT_PRESCALE_64	64
 #define CDNS_WDT_PRESCALE_512	512
 #define CDNS_WDT_PRESCALE_4096	4096
+#define CDNS_WDT_PRESCALE_SELECT_8	0
 #define CDNS_WDT_PRESCALE_SELECT_64	1
 #define CDNS_WDT_PRESCALE_SELECT_512	2
 #define CDNS_WDT_PRESCALE_SELECT_4096	3
 
-/* Input clock frequency */
-#define CDNS_WDT_CLK_10MHZ	10000000
-#define CDNS_WDT_CLK_75MHZ	75000000
+/* Base input clock frequency */
+#define CDNS_WDT_CLK_32KHZ 32768
 
 /* Counter maximum value */
 #define CDNS_WDT_COUNTER_MAX 0xFFF
@@ -304,7 +305,16 @@ static int cdns_wdt_probe(struct platform_device *pdev)
 	}
 
 	clock_f = clk_get_rate(wdt->clk);
-	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
+	if (clock_f < CDNS_WDT_CLK_32KHZ) {
+		dev_err(&pdev->dev, "cannot find suitable clock prescaler\n");
+		return -ERANGE;
+	} else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_8) {
+		wdt->prescaler = CDNS_WDT_PRESCALE_8;
+		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_8;
+	} else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_64) {
+		wdt->prescaler = CDNS_WDT_PRESCALE_64;
+		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_64;
+	} else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_512) {
 		wdt->prescaler = CDNS_WDT_PRESCALE_512;
 		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
 	} else {
-- 
2.17.2

Re: [PATCH v2 1/4] watchdog: cadence_wdt: Move clock detection eariler in probe

[Guenter Roeck]

On Fri, Jul 05, 2019 at 11:46:02AM +0000, Melin Tomas wrote:
> Timeout calculation needs clock frequency, so init clock and calculate
> prescaler value eariler in the probe.
> 
earlier; also in subject line

> Preparational step for calculating maximum and minimum timeout values
> for driver.
> 
> Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
> ---
>  drivers/watchdog/cadence_wdt.c | 32 ++++++++++++++++----------------
>  1 file changed, 16 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
> index c3924356d173..415bd6dd1edb 100644
> --- a/drivers/watchdog/cadence_wdt.c
> +++ b/drivers/watchdog/cadence_wdt.c
> @@ -295,6 +295,22 @@ static int cdns_wdt_probe(struct platform_device *pdev)
>  	if (!wdt)
>  		return -ENOMEM;
>  
> +	wdt->clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(wdt->clk)) {
> +		dev_err(&pdev->dev, "input clock not found\n");
> +		ret = PTR_ERR(wdt->clk);
> +		return ret;

		return PTR_ERR(wdt->clk);

[ ok, that is from the old code ... ]

> +	}
> +
> +	clock_f = clk_get_rate(wdt->clk);
> +	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
> +		wdt->prescaler = CDNS_WDT_PRESCALE_512;
> +		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
> +	} else {
> +		wdt->prescaler = CDNS_WDT_PRESCALE_4096;
> +		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
> +	}
> +
>  	cdns_wdt_device = &wdt->cdns_wdt_device;
>  	cdns_wdt_device->info = &cdns_wdt_info;
>  	cdns_wdt_device->ops = &cdns_wdt_ops;
> @@ -334,28 +350,12 @@ static int cdns_wdt_probe(struct platform_device *pdev)
>  	watchdog_stop_on_reboot(cdns_wdt_device);
>  	watchdog_set_drvdata(cdns_wdt_device, wdt);
>  
> -	wdt->clk = devm_clk_get(&pdev->dev, NULL);
> -	if (IS_ERR(wdt->clk)) {
> -		dev_err(&pdev->dev, "input clock not found\n");
> -		ret = PTR_ERR(wdt->clk);
> -		return ret;
> -	}
> -
>  	ret = clk_prepare_enable(wdt->clk);
>  	if (ret) {
>  		dev_err(&pdev->dev, "unable to enable clock\n");
>  		return ret;
>  	}
>  
The substantial difference here is that clk_prepare_enable() was called
before the actual clock rate was retrieved. I don't know if that makes
a substantial difference, but on the other side I don't see why the above
code isn't moved as well. What I _do_ see, however, is that this patch
isn't based on the latest mainline kenrel, since mainline has a call to
devm_add_action_or_reset() after clk_prepare_enable(). Please rebase.

> -	clock_f = clk_get_rate(wdt->clk);
> -	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
> -		wdt->prescaler = CDNS_WDT_PRESCALE_512;
> -		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
> -	} else {
> -		wdt->prescaler = CDNS_WDT_PRESCALE_4096;
> -		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
> -	}
> -
>  	spin_lock_init(&wdt->io_lock);
>  
>  	ret = watchdog_register_device(cdns_wdt_device);

Re: [PATCH v2 2/4] watchdog: cadence_wdt: Calculate actual timeout limits

[Guenter Roeck]

On Fri, Jul 05, 2019 at 11:46:02AM +0000, Melin Tomas wrote:
> Maximum and minimum timeout values depend on the actual input clock
> frequency and prescaler selection.
> 
> Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
> ---
>  drivers/watchdog/cadence_wdt.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
> index 415bd6dd1edb..87b767c87bb6 100644
> --- a/drivers/watchdog/cadence_wdt.c
> +++ b/drivers/watchdog/cadence_wdt.c
> @@ -18,9 +18,6 @@
>  #include <linux/watchdog.h>
>  
>  #define CDNS_WDT_DEFAULT_TIMEOUT	10
> -/* Supports 1 - 516 sec */
> -#define CDNS_WDT_MIN_TIMEOUT	1
> -#define CDNS_WDT_MAX_TIMEOUT	516
>  
>  /* Restart key */
>  #define CDNS_WDT_RESTART_KEY 0x00001999
> @@ -28,6 +25,10 @@
>  /* Counter register access key */
>  #define CDNS_WDT_REGISTER_ACCESS_KEY 0x00920000
>  
> +/* Counter control register, counter restart values */
> +#define CDNS_WDT_CCR_CRV_MIN 0xFFF
> +#define CDNS_WDT_CCR_CRV_MAX 0xFFFFFF
> +
>  /* Counter value divisor */
>  #define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000
>  
> @@ -315,8 +316,10 @@ static int cdns_wdt_probe(struct platform_device *pdev)
>  	cdns_wdt_device->info = &cdns_wdt_info;
>  	cdns_wdt_device->ops = &cdns_wdt_ops;
>  	cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
> -	cdns_wdt_device->min_timeout = CDNS_WDT_MIN_TIMEOUT;
> -	cdns_wdt_device->max_timeout = CDNS_WDT_MAX_TIMEOUT;
> +	cdns_wdt_device->min_timeout =
> +		CDNS_WDT_CCR_CRV_MIN * wdt->prescaler / clock_f;
> +	cdns_wdt_device->max_timeout =
> +		CDNS_WDT_CCR_CRV_MAX * wdt->prescaler / clock_f;

clock_f can at least in theory be 0. So far that didn't matter as
much, but now it would crash the kernel. Please add a respective
check into the code.

>  
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	wdt->regs = devm_ioremap_resource(&pdev->dev, res);

Re: [PATCH v2 3/4] watchdog: cadence_wdt: Group struct member init statements

[Guenter Roeck]

On Fri, Jul 05, 2019 at 11:46:03AM +0000, Melin Tomas wrote:
> Move init statement and remove stray comment.
> 
> Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
> ---
>  drivers/watchdog/cadence_wdt.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
> index 87b767c87bb6..4657800d9d8e 100644
> --- a/drivers/watchdog/cadence_wdt.c
> +++ b/drivers/watchdog/cadence_wdt.c
> @@ -313,6 +313,7 @@ static int cdns_wdt_probe(struct platform_device *pdev)
>  	}
>  	
>  	cdns_wdt_device = &wdt->cdns_wdt_device;
> +	cdns_wdt_device->parent = &pdev->dev;

In the upstream kernel, we have
	struct device *dev = &pdev->dev;
and
	cdns_wdt_device->parent = dev;

so this patch no longer applies.

>  	cdns_wdt_device->info = &cdns_wdt_info;
>  	cdns_wdt_device->ops = &cdns_wdt_ops;
>  	cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
> @@ -340,9 +341,6 @@ static int cdns_wdt_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> -	/* Initialize the members of cdns_wdt structure */
> -	cdns_wdt_device->parent = &pdev->dev;
> -
>  	ret = watchdog_init_timeout(cdns_wdt_device, wdt_timeout, &pdev->dev);
>  	if (ret) {
>  		dev_err(&pdev->dev, "unable to set timeout value\n");

Re: [PATCH v2 4/4] watchdog: cadence_wdt: Support all available prescaler values

[Guenter Roeck]

On Fri, Jul 05, 2019 at 11:46:04AM +0000, Melin Tomas wrote:
> Cadence watchdog HW supports prescaler values of
> 8, 64, 512 and 4096.
> 
> Add support to select prescaler values of 8 and 64 for lower
> input clock frequencies.
> 
> Prescaler value is selected to keep timeout resolution of 1 second.
> For clock frequencies below 32kHz, 1 second resolution does
> no longer hold, thereby returning an error.
> 
> Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
> ---
>  drivers/watchdog/cadence_wdt.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
> index 4657800d9d8e..39109b5721c1 100644
> --- a/drivers/watchdog/cadence_wdt.c
> +++ b/drivers/watchdog/cadence_wdt.c
> @@ -33,16 +33,17 @@
>  #define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000
>  
>  /* Clock prescaler value and selection */
> +#define CDNS_WDT_PRESCALE_8	8
>  #define CDNS_WDT_PRESCALE_64	64
>  #define CDNS_WDT_PRESCALE_512	512
>  #define CDNS_WDT_PRESCALE_4096	4096
> +#define CDNS_WDT_PRESCALE_SELECT_8	0
>  #define CDNS_WDT_PRESCALE_SELECT_64	1
>  #define CDNS_WDT_PRESCALE_SELECT_512	2
>  #define CDNS_WDT_PRESCALE_SELECT_4096	3
>  
> -/* Input clock frequency */
> -#define CDNS_WDT_CLK_10MHZ	10000000
> -#define CDNS_WDT_CLK_75MHZ	75000000
> +/* Base input clock frequency */
> +#define CDNS_WDT_CLK_32KHZ 32768
>  
>  /* Counter maximum value */
>  #define CDNS_WDT_COUNTER_MAX 0xFFF
> @@ -304,7 +305,16 @@ static int cdns_wdt_probe(struct platform_device *pdev)
>  	}
>  
>  	clock_f = clk_get_rate(wdt->clk);
> -	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
> +	if (clock_f < CDNS_WDT_CLK_32KHZ) {
> +		dev_err(&pdev->dev, "cannot find suitable clock prescaler\n");
> +		return -ERANGE;

	/* Math result not representable */

is a bit misleading here. I understand there isn't a good option,
but using math errors isn't it. Just use -EINVAL if you don't have
a better idea. It might also make sense to display the returned
clock frequency.

> +	} else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_8) {
> +		wdt->prescaler = CDNS_WDT_PRESCALE_8;
> +		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_8;
> +	} else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_64) {
> +		wdt->prescaler = CDNS_WDT_PRESCALE_64;
> +		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_64;
> +	} else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_512) {
>  		wdt->prescaler = CDNS_WDT_PRESCALE_512;
>  		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
>  	} else {