On 05/25/2015 05:03 AM, fu.wei@linaro.org wrote:

+/*
+ * help functions for accessing 32bit registers of SBSA Generic Watchdog
+ */
+static void sbsa_gwdt_cf_write(unsigned int reg, u32 val,
+			       struct watchdog_device *wdd)
+{
+	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
+
+	writel_relaxed(val, gwdt->control_base + reg);
+}
+
+static void sbsa_gwdt_rf_write(unsigned int reg, u32 val,
+			       struct watchdog_device *wdd)
+{
+	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
+
+	writel_relaxed(val, gwdt->refresh_base + reg);
+}
+
+static u32 sbsa_gwdt_cf_read(unsigned int reg, struct watchdog_device *wdd)
+{
+	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
+
+	return readl_relaxed(gwdt->control_base + reg);
+}

I don't understand the value of these functions.  You're just adding 
overhead to each read and write by dereferencing wdd every time.  I 
would get rid of them and just call readl_relaxed() and writel_relaxed() 
directly.

+/*
+ * help functions for accessing 64bit WCV register
+ */
+static u64 sbsa_gwdt_get_wcv(struct watchdog_device *wdd)
+{
+	u32 wcv_lo, wcv_hi;
+
+	do {
+		wcv_hi = sbsa_gwdt_cf_read(SBSA_GWDT_WCV_HI, wdd);
+		wcv_lo = sbsa_gwdt_cf_read(SBSA_GWDT_WCV_LO, wdd);
+	} while (wcv_hi != sbsa_gwdt_cf_read(SBSA_GWDT_WCV_HI, wdd));

Please add a comment indicating that you're trying to read WCV atomically.

+
+	return (((u64)wcv_hi << 32) | wcv_lo);
+}

How about defining this macro:

#define make64(high, low) (((u64)(high) << 32) | (low))

and using it instead?  That makes the code easier to read.

+
+static void sbsa_gwdt_set_wcv(struct watchdog_device *wdd, u64 value)
+{
+	u32 wcv_lo, wcv_hi;
+
+	wcv_lo = value & U32_MAX;
+	wcv_hi = (value >> 32) & U32_MAX;

Use upper_32_bits() and lower_32_bits() instead.

+
+	sbsa_gwdt_cf_write(SBSA_GWDT_WCV_HI, wcv_hi, wdd);
+	sbsa_gwdt_cf_write(SBSA_GWDT_WCV_LO, wcv_lo, wdd);
+}
+
+static void reload_timeout_to_wcv(struct watchdog_device *wdd)

This should be sbsa_gwdt_reload_timeout_to_wcv()

+{
+	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
+	u64 wcv;
+
+	wcv = arch_counter_get_cntvct() +
+		(u64)(wdd->timeout - wdd->pretimeout) * gwdt->clk;
+
+	sbsa_gwdt_set_wcv(wdd, wcv);

Shouldn't you program WCV and WOR together?

+static int sbsa_gwdt_set_pretimeout(struct watchdog_device *wdd,
+				    unsigned int pretimeout)
+{
+	struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
+	u32 wor;
+
+	wdd->pretimeout = pretimeout;
+	sbsa_gwdt_update_limits(wdd);
+
+	if (!pretimeout)
+		/* gives sbsa_gwdt_start a chance to setup timeout */
+		wor = gwdt->clk;
+	else
+		wor = pretimeout * gwdt->clk;
+
+	/* refresh the WOR, that will cause an explicit watchdog refresh */
+	sbsa_gwdt_cf_write(SBSA_GWDT_WOR, wor, wdd);

Why not just ping the watchdog explicitely?

+static irqreturn_t sbsa_gwdt_interrupt(int irq, void *dev_id)
+{
+	struct sbsa_gwdt *gwdt = (struct sbsa_gwdt *)dev_id;
+	struct watchdog_device *wdd = &gwdt->wdd;
+	u32 status;
+
+	status = sbsa_gwdt_cf_read(SBSA_GWDT_WCS, wdd);
+
+	if (status & SBSA_GWDT_WCS_WS0)

This should always be true.  Instead of reading WCS, I think you should 
just panic().

+static int sbsa_gwdt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct sbsa_gwdt *gwdt;
+	struct watchdog_device *wdd;
+	struct resource *res;
+	void *rf_base, *cf_base;
+	int irq;
+	u32 clk, status;
+	int ret = 0;
+	u64 first_period_max = U64_MAX;
+
+	/*
+	 * Get the frequency of system counter from
+	 * the cp15 interface of ARM Generic timer
+	 */
+	clk = arch_timer_get_cntfrq();
+	if (!clk) {

You have

	depends on ARM_ARCH_TIMER

in your Kconfig, so you don't need to check the return of 
arch_timer_get_cntfrq().  It can never be zero.

Also, I would not use the variable name 'clk', because that's usually 
used for a "struct clk" object.  I would call this "freq" instead.

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