Adding movable PCIe BARs support in snd_hda_intel

[Andrey Grodzovsky]

Just an update, i found the issue which was actually to wake up the HW
before doing stop/restart (using pm_runtime_get_sync), also handled
protecting from concurrent snd_pcm_ioctls accessing the registers
while the BAR is unmapped. Can go through BAR move while aplay is
running now.

Once again, would be happy for any comments on the code - 
https://cgit.freedesktop.org/~agrodzov/linux/log/?h=yadro/pcie_hotplug/movable_bars_v9.1 


Andrey

On 2021-03-19 5:22 p.m., Andrey Grodzovsky wrote:
> Hi, I am working on adding AMD related drivers support for PCIe BARs 
> move feature developed by Sergei 
> (https://linuxplumbersconf.org/event/7/contributions/847/attachments/584/1035/lpc2020_sergmir.pdf). 
> 
> His feature is still not upstream, all his code and mine on top can be 
> seen here - 
> https://cgit.freedesktop.org/~agrodzov/linux/log/?h=yadro/pcie_hotplug/movable_bars_v9.1 
> 
> I did basic implementation fro amdgpu driver and now I am doing the same 
> for snd_hda_intel to support our on GPU Azalia audio chips. This 
> relevant commit is here - 
> https://cgit.freedesktop.org/~agrodzov/linux/commit/?h=yadro/pcie_hotplug/movable_bars_v9.1&id=7ec0f60633e898cb941cebb3cd18aae1374fc365 
> 
> Any driver that wants to support movable BARs needs to implement 
> rescan_prepare, rescan_done and bar_fixed callbacks where rescan_prepare 
> needs to stop HW/SW and unamp all MMIO mappings and rescan_done needs to 
> ioremap the BAR from it's new MMIO location and restart HW/SW.
> 
> I am able currently to trigger BARs move by sysfs using 
> "/sys/bus/pci/rescan" and the driver will go through the sequence I 
> described above without hangs. Problem is that after this when i try to 
> use mplayer I am getting following errors:
> 
> andrey at andrey-test:~$ sudo mplayer -ao alsa:device=hw=0.3 
> Downloads/file_example_MP3_5MG.mp3
> MPlayer 1.3.0 (Debian), built with gcc-9 (C) 2000-2016 MPlayer Team
> do_connect: could not connect to socket
> connect: No such file or directory
> Failed to open LIRC support. You will not be able to use your remote 
> control.
> 
> Playing Downloads/file_example_MP3_5MG.mp3.
> libavformat version 58.29.100 (external)
> Audio only file format detected.
> Load subtitles in Downloads/
> ==========================================================================
> Opening audio decoder: [mpg123] MPEG 1.0/2.0/2.5 layers I, II, III
> AUDIO: 44100 Hz, 2 ch, s16le, 320.0 kbit/22.68% (ratio: 40000->176400)
> Selected audio codec: [mpg123] afm: mpg123 (MPEG 1.0/2.0/2.5 layers I, 
> II, III)
> ==========================================================================
> AO: [alsa] 44100Hz 2ch s16le (2 bytes per sample)
> Video: no video
> Starting playback...
> A:   0.1 (00.0) of 132.0 (02:12.0) ??,?%
> Audio device got stuck!
> 
> and in dmesg I see
> [  365.355518] snd_hda_codec_hdmi hdaudioC0D0: Unable to sync register 
> 0x2f0d00. -5
> 
> Also I see 296.619014] snd_hda_intel 0000:0a:00.1: CORB reset timeout#2, 
> CORBRP = 65535 error during the rescan_done callback execution
> 
> I know it has to do with the move of BAR's MMIO address because when i
> disallow BAR migration by returning true from bar_fixed callback I have 
> no such errors and mplayer works fine.
> 
> I enabled MMIO trace and didn't see that post BAR move there is a wrong 
> MMIO access - all of them are from the new MMIO base offset - 0xfcd80000 
> (trace attached including mmio trace and dmesg)
> 
> I would be happy for any idea on this and any comment on the correctness 
> of my sequence in the code
> 
> Andrey