[2/2] watchdog: aspeed: Support configuration of external signal properties

[Guenter Roeck <linux@roeck-us.net>]

On Wed, Aug 02, 2017 at 02:15:29PM +0930, Andrew Jeffery wrote:
> Add support for configuring the drive strength and polarity on the
> AST2500, and the pulse duration on both the AST2400 and AST2500.
> 
> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
> Tested-by: Matt Spinler <mspinler@linux.vnet.ibm.com>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  drivers/watchdog/aspeed_wdt.c | 105 ++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 102 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/watchdog/aspeed_wdt.c b/drivers/watchdog/aspeed_wdt.c
> index c707ab647922..79cc766cd30f 100644
> --- a/drivers/watchdog/aspeed_wdt.c
> +++ b/drivers/watchdog/aspeed_wdt.c
> @@ -23,9 +23,21 @@ struct aspeed_wdt {
>  	u32			ctrl;
>  };
>  
> +struct aspeed_wdt_config {
> +	u32 ext_pulse_width_mask;
> +};
> +
> +static const struct aspeed_wdt_config ast2400_config = {
> +	.ext_pulse_width_mask = 0xff,
> +};
> +
> +static const struct aspeed_wdt_config ast2500_config = {
> +	.ext_pulse_width_mask = 0xfffff,
> +};
> +
>  static const struct of_device_id aspeed_wdt_of_table[] = {
> -	{ .compatible = "aspeed,ast2400-wdt" },
> -	{ .compatible = "aspeed,ast2500-wdt" },
> +	{ .compatible = "aspeed,ast2400-wdt", .data = &ast2400_config },
> +	{ .compatible = "aspeed,ast2500-wdt", .data = &ast2500_config },
>  	{ },
>  };
>  MODULE_DEVICE_TABLE(of, aspeed_wdt_of_table);
> @@ -43,6 +55,38 @@ MODULE_DEVICE_TABLE(of, aspeed_wdt_of_table);
>  #define   WDT_CTRL_RESET_SYSTEM		BIT(1)
>  #define   WDT_CTRL_ENABLE		BIT(0)
>  
> +/*
> + * WDT_RESET_WIDTH controls the characteristics of the external pulse (if
> + * enabled), specifically:
> + *
> + * * Pulse duration
> + * * Drive mode: push-pull vs open-drain
> + * * Polarity: Active high or active low
> + *
> + * Pulse duration configuration is available on both the AST2400 and AST2500,
> + * though the field changes between SoCs:
> + *
> + * AST2400: Bits 7:0
> + * AST2500: Bits 19:0
> + *
> + * This difference is captured in struct aspeed_wdt_config.
> + *
> + * The AST2500 exposes the drive mode and polarity options, but not in a
> + * regular fashion. For read purposes, bit 31 represents active high or low,
> + * and bit 30 represents push-pull or open-drain. With respect to write, magic
> + * values need to be written to the top byte to change the state of the drive
> + * mode and polarity bits. Any other value written to the top byte has no
> + * effect on the state of the drive mode or polarity bits. However, the pulse
> + * width value must be preserved (as desired) if written.
> + */
> +#define WDT_RESET_WIDTH		0x18
> +#define   WDT_RESET_WIDTH_ACTIVE_HIGH	BIT(31)
> +#define     WDT_ACTIVE_HIGH_MAGIC	(0xA5 << 24)
> +#define     WDT_ACTIVE_LOW_MAGIC	(0x5A << 24)
> +#define   WDT_RESET_WIDTH_PUSH_PULL	BIT(30)
> +#define     WDT_PUSH_PULL_MAGIC		(0xA8 << 24)
> +#define     WDT_OPEN_DRAIN_MAGIC	(0x8A << 24)
> +
>  #define WDT_RESTART_MAGIC	0x4755
>  
>  /* 32 bits at 1MHz, in milliseconds */
> @@ -139,10 +183,13 @@ static const struct watchdog_info aspeed_wdt_info = {
>  
>  static int aspeed_wdt_probe(struct platform_device *pdev)
>  {
> +	const struct aspeed_wdt_config *config;
> +	const struct of_device_id *ofdid;
>  	struct aspeed_wdt *wdt;
>  	struct resource *res;
>  	struct device_node *np;
>  	const char *reset_type;
> +	u32 duration;
>  	int ret;
>  
>  	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
> @@ -167,13 +214,19 @@ static int aspeed_wdt_probe(struct platform_device *pdev)
>  	wdt->wdd.timeout = WDT_DEFAULT_TIMEOUT;
>  	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
>  
> +	np = pdev->dev.of_node;
> +
> +	ofdid = of_match_node(aspeed_wdt_of_table, np);
> +	if (!ofdid)
> +		return -EINVAL;
> +	config = ofdid->data;
> +
>  	wdt->ctrl = WDT_CTRL_1MHZ_CLK;
>  
>  	/*
>  	 * Control reset on a per-device basis to ensure the
>  	 * host is not affected by a BMC reboot
>  	 */
> -	np = pdev->dev.of_node;
>  	ret = of_property_read_string(np, "aspeed,reset-type", &reset_type);
>  	if (ret) {
>  		wdt->ctrl |= WDT_CTRL_RESET_MODE_SOC | WDT_CTRL_RESET_SYSTEM;
> @@ -197,6 +250,52 @@ static int aspeed_wdt_probe(struct platform_device *pdev)
>  		set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
>  	}
>  
> +	if (of_device_is_compatible(np, "aspeed,ast2500-wdt")) {
> +		u32 reg = readl(wdt->base + WDT_RESET_WIDTH);
> +
> +		reg &= config->ext_pulse_width_mask;
> +		if (of_property_read_bool(np, "aspeed,ext-push-pull"))
> +			reg |= WDT_PUSH_PULL_MAGIC;
> +		else
> +			reg |= WDT_OPEN_DRAIN_MAGIC;
> +
> +		writel(reg, wdt->base + WDT_RESET_WIDTH);
> +
> +		reg &= config->ext_pulse_width_mask;
> +		if (of_property_read_bool(np, "aspeed,ext-active-high"))
> +			reg |= WDT_ACTIVE_HIGH_MAGIC;
> +		else
> +			reg |= WDT_ACTIVE_LOW_MAGIC;
> +
> +		writel(reg, wdt->base + WDT_RESET_WIDTH);
> +	}
> +
> +	if (!of_property_read_u32(np, "aspeed,ext-pulse-duration", &duration)) {
> +		u32 max_duration = config->ext_pulse_width_mask + 1;
> +
> +		if (duration == 0 || duration > max_duration) {
> +			dev_err(&pdev->dev, "Invalid pulse duration: %uus\n",
> +					duration);
> +			duration = max(1U, min(max_duration, duration));
> +			dev_info(&pdev->dev, "Pulse duration set to %uus\n",
> +					duration);
> +		}
> +
> +		/*
> +		 * The watchdog is always configured with a 1MHz source, so
> +		 * there is no need to scale the microsecond value. However we
> +		 * need to offset it - from the datasheet:
> +		 *
> +		 * "This register decides the asserting duration of wdt_ext and
> +		 * wdt_rstarm signal. The default value is 0xFF. It means the
> +		 * default asserting duration of wdt_ext and wdt_rstarm is
> +		 * 256us."
> +		 *
> +		 * This implies a value of 0 gives a 1us pulse.
> +		 */
> +		writel(duration - 1, wdt->base + WDT_RESET_WIDTH);
> +	}
> +
>  	ret = devm_watchdog_register_device(&pdev->dev, &wdt->wdd);
>  	if (ret) {
>  		dev_err(&pdev->dev, "failed to register\n");