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Message-ID: <20170815022116.GA2201@roeck-us.net>
Date: Mon, 14 Aug 2017 19:21:16 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Andrew Jeffery <andrew@...id.au>
Cc: linux-watchdog@...r.kernel.org, wim@...ana.be, robh+dt@...nel.org,
mark.rutland@....com, joel@....id.au, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-aspeed@...ts.ozlabs.org,
openbmc@...ts.ozlabs.org
Subject: Re: [2/2] watchdog: aspeed: Support configuration of external signal
properties
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@...id.au>
> Tested-by: Matt Spinler <mspinler@...ux.vnet.ibm.com>
Reviewed-by: Guenter Roeck <linux@...ck-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");
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