Adding movable PCIe BARs support in snd_hda_intel

[Andrey Grodzovsky]

Few comments -

1) Why we don't use snd_power_wait_and_ref in patch 3 in the common 
handler ?
Don't we want the PCI rescan sequence to 'wait for' any in flight
taks that might be accessing registers and not only read/write/tlv 
accesses ?

2) Possible deadlock -
In azx_rescan_prepare - you put the card into SNDRV_CTL_POWER_D3hot
first and then 'wait for' all in flight tasks with the refcount.
The in flight tasks on the other hand, using snd_power_wait_and_ref,
may have already bumped up the refcount and now 'wait for' the card
to go into SNDRV_CTL_POWER_D0 which can't happen since PCI rescan
waits for the refocunt to drop to 0 before proceeding.

Instead of snd_power_wait_and_ref can't we just call snd_power_ref
in common IOCTL before checking for power_state != SNDRV_CTL_POWER_D0 ?
Or is it because you don't want to fail IOCTLs ?

Andrey


On 2021-03-24 4:36 p.m., Takashi Iwai wrote:
> On Wed, 24 Mar 2021 16:43:02 +0100,
> Andrey Grodzovsky wrote:
>>
>> I merged the patches, since it looks like my branch
>> is older I didn't have chip->init_failed member and
>> also seems there was a typo on ur side as there
>> is no flush_work_sync, only flush_work which waits
>> synchronously anyway.
> 
> Ah that must be some typos I forgot to refresh.
> 
>> Everything works fine when testing with maplyer running concurrently
>> to PCI rescan cycle.
>>
>> Can you be more specific what are those get/put calls,
>> I am thinking about some waitqueue to wait on in rescan_prepare
>> after setting snd_hdac_bus_freeze,
>> on wakeup it checks that a counter dropped back to zero.
>> Not sure on which entity to hang this counter ?
> 
> It's something like the patch 6 in the v2 series below.
> At this time, I dropped snd_hdac_bus_freeze() as this is basically
> useless.
> 
> Maybe this is no optimal implementation and we might improve a bit,
> but I guess you get an idea from that.
> 
> Also I added ifdef CONFIG_PM in the last patch as it obviously depends
> on it.  It could be put in Kconfig somehow, too, but a simple ifdef
> should suffice.
> 
> 
> Takashi
>