On 03/03/2015 05:07 PM, Mark Brown wrote:
On Tue, Mar 03, 2015 at 04:26:32PM +0200, Peter Ujfalusi wrote:
@@ -553,6 +554,7 @@ static int __davinci_mcasp_set_clkdiv(struct snd_soc_dai *dai, int div_id, return -EINVAL; }
- pm_runtime_put_sync(mcasp->dev);
Why the _put_sync()s? I know it's more symmetrical but I don't see a need to wait and it means we may be able to avoid some unneeded power cycles.
True, the _sync can be dropped. I guess I used it just for symmetry ;)
@@ -1078,6 +1082,9 @@ static int davinci_mcasp_suspend(struct snd_soc_dai *dai) u32 reg; int i;
- if (!dai->active)
pm_runtime_get_sync(mcasp->dev);- for (i = 0; i < ARRAY_SIZE(context_regs); i++) context->config_regs[i] = mcasp_get_reg(mcasp, context_regs[i]);
@@ -1094,6 +1101,8 @@ static int davinci_mcasp_suspend(struct snd_soc_dai *dai) context->xrsr_regs[i] = mcasp_get_reg(mcasp, DAVINCI_MCASP_XRSRCTL_REG(i));
- pm_runtime_put_sync(mcasp->dev);
On first glance this looks unbalanced without the active check in the put case. I'd also need to check if runtime resume works OK in suspend context, I guess it must but there were issues in the past (the more common idiom is to not suspend if we're already runtime powered down but obviously here we're actually doing extra work).
McASP is only going to loose it's context when the whole device goes to suspend. In this case I need to save the registers which I need to restore in resume time.
I see there's actually a balanced put in the resume path... I see what's going on here but I'm thinking that perhaps something more explicit that calls the ops directly and checks pm_runtime_is_enabled() might be clearer?
The issue with the pm_runtime_is_enabled() is going to be in the resume path, as I did get_sync() it will return true at the end all the time.
In order to save/restore McASP register the IP need to be enabled.
-If we suspend/resume while no audio was running: dai->active is false, pm_runtime is disabled when the davinci_mcasp_suspend() is called. So I need to get_sync(), save context and put_sync() so we are in balance. In resume, dai->active is false, pm_runtime is disabled, so I again need to get_sync(), restore registers and put_sync() so we are in balance again and mcasp stay disabled.
-If we suspend/resume while audio was running: dai->active is true, pm_runtime is enabled when the davinci_mcasp_suspend() is called. I don't need the get_sync(), save context and put_sync() so I release all the resources needed for McASP. runtime_pm will be disabled. In resume dai->active is true, pm_runtime is disabled. I need to get_sync(), restore registers and since dai->active is true I should not put_sync() to keep McASP enabled and be able to resume the audio.
I think this hassle is needed if I want to achieve what subject describes.
Unconditionally do the power down/up at the end with a direct call outside of runtime PM and then make the checks at the top/bottom be "if it's runtime suspended then...". That's also more direct about what's actually being checked and hence less risk that some future changes would go wrong.