On Fri, Dec 1, 2017 at 12:44 PM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
> Quoting Sean Paul (2017-12-01 17:20:24)
>> /**
>> - * _wait_for - magic (register) wait macro
>> + * __wait_for - magic wait macro
>> *
>> - * Does the right thing for modeset paths when run under kdgb or similar atomic
>> - * contexts. Note that it's important that we check the condition again after
>> + * Macro to help avoid open coding check/wait/timeout patterns, will do the
>> + * right think wrt to choosing msleep vs usleep_range based on how long the wait
>> + * interval is. Note that it's important that we check the condition again after
>> * having timed out, since the timeout could be due to preemption or similar and
>> * we've never had a chance to check the condition before the timeout.
>> */
>> -#define _wait_for(COND, US, W) ({ \
>> +#define __wait_for(OP, COND, US, W) ({ \
>> unsigned long timeout__ = jiffies + usecs_to_jiffies(US) + 1; \
>> int ret__; \
>> might_sleep(); \
>> for (;;) { \
>> bool expired__ = time_after(jiffies, timeout__); \
>> + OP; \
>> if (COND) { \
>> ret__ = 0; \
>> break; \
>> @@ -62,11 +64,16 @@
>> ret__ = -ETIMEDOUT; \
>> break; \
>> } \
>> - usleep_range((W), (W) * 2); \
>> + if (W > (20 * 1000)) \
>> + msleep(W / 1000); \
>> + else \
>> + usleep_range((W), (W) * 2); \
>
> The current wait_for() is a little more complicated nowadays (variable
> W).
>
Hmm, am I based off the wrong tree? I'm using drm-intel-next.
> Are ms intervals going to be that common? Using a state-machine springs
> to mind, but you could argue that msleep() is just a yield. Using msleep
> though is going to leave D processes visible and a bump in load :|
>
Probably uncommon, but at the very least, I need one. I wouldn't feel
comfortable handling such a large wait using usleep_range.
Sean
>> } \
>> ret__; \
>> })
>>
>> +#define _wait_for(COND, US, W) __wait_for(;,(COND), US, W)
>> +
>> #define wait_for(COND, MS) _wait_for((COND), (MS) * 1000, 1000)
>>
>> /* If CONFIG_PREEMPT_COUNT is disabled, in_atomic() always reports false. */
>> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
>> index b4621271e7a2..c851b0c0602d 100644
>> --- a/drivers/gpu/drm/i915/intel_uncore.c
>> +++ b/drivers/gpu/drm/i915/intel_uncore.c
>> @@ -1770,12 +1770,14 @@ int __intel_wait_for_register_fw(struct drm_i915_private *dev_priv,
>> }
>>
>> /**
>> - * intel_wait_for_register - wait until register matches expected state
>> + * __intel_wait_for_register - wait until register matches expected state
>> * @dev_priv: the i915 device
>> * @reg: the register to read
>> * @mask: mask to apply to register value
>> * @value: expected value
>> - * @timeout_ms: timeout in millisecond
>> + * @fast_timeout_us: fast timeout in microsecond for atomic/tight wait
>> + * @slow_timeout_ms: slow timeout in millisecond
>> + * @out_value: optional placeholder to hold registry value
>> *
>> * This routine waits until the target register @reg contains the expected
>> * @value after applying the @mask, i.e. it waits until ::
>> @@ -1786,15 +1788,18 @@ int __intel_wait_for_register_fw(struct drm_i915_private *dev_priv,
>> *
>> * Returns 0 if the register matches the desired condition, or -ETIMEOUT.
>> */
>> -int intel_wait_for_register(struct drm_i915_private *dev_priv,
>> +int __intel_wait_for_register(struct drm_i915_private *dev_priv,
>> i915_reg_t reg,
>> u32 mask,
>> u32 value,
>> - unsigned int timeout_ms)
>> + unsigned int fast_timeout_us,
>> + unsigned int slow_timeout_ms,
>> + u32 *out_value)
>> {
>> unsigned fw =
>> intel_uncore_forcewake_for_reg(dev_priv, reg, FW_REG_READ);
>> int ret;
>> + u32 reg_value;
>>
>> might_sleep();
>>
>> @@ -1803,14 +1808,18 @@ int intel_wait_for_register(struct drm_i915_private *dev_priv,
>>
>> ret = __intel_wait_for_register_fw(dev_priv,
>> reg, mask, value,
>> - 2, 0, NULL);
>> + fast_timeout_us, 0, ®_value);
>>
>> intel_uncore_forcewake_put__locked(dev_priv, fw);
>> spin_unlock_irq(&dev_priv->uncore.lock);
>>
>> if (ret)
>> - ret = wait_for((I915_READ_NOTRACE(reg) & mask) == value,
>> - timeout_ms);
>> + ret = __wait_for(reg_value = I915_READ_NOTRACE(reg),
>> + (reg_value & mask) == value,
>> + slow_timeout_ms * 1000, 1000);
>> +
>> + if (out_value)
>> + *out_value = reg_value;
>
> Looks good.
> -Chris
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