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SubjectRe: [PATCH v3 5/6] Watchdog: introduce ARM SBSA watchdog driver
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.

--
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.


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