Re: [Sound-open-firmware] [PATCH v3 07/14] ASoC: SOF: Add DSP firmware logger support

Takashi Iwai
2018-12-12T16:12:44Z

On Wed, 12 Dec 2018 17:04:42 +0100,
Pierre-Louis Bossart wrote:
>
>
> On 12/12/18 5:11 AM, Takashi Iwai wrote:
> > On Tue, 11 Dec 2018 22:23:11 +0100,
> > Pierre-Louis Bossart wrote:
> >> From: Liam Girdwood <liam.r.girdwood@linux.intel.com>
> >>
> >> This patch adds support for real-time DSP logging (timestamped events
> >> and bespoke binary data) for firmware debug. The current solution
> >> relies on DMA transfers to system memory that is then accessed by
> >> userspace tools such as sof-logger. For Intel platforms, two types of
> >> DMAs are currently used (GP-DMA for Baytrail/CherryTrail and HDaudio
> >> DMA for SKL+)
> >>
> >> Due to historical reasons, the driver code follows the DSP firmware
> >> conventions and refers to 'traces', but it is currently unrelated to
> >> the Linux trace subsystem. Future solutions will include support for
> >> more advanced hardware (e.g. MIPI Sys-T), additional formats and the
> >> ability to enable/disable specific traces dynamically.
> > So what's the reason not to use Linux standard tracing infrastructure?
>
> I obviously failed to convey the intent in the commit message :-(
>
> What we have today is just a DMA-based transfers of 'trace' data into
> a ring buffer. That's it. it's very similar to what always existed on
> Atom and Skylake, just more transparent and released for upstream
> reviews this time.
>
> Is it optimal or final? Absolutely not. There will be evolutions such as
>
> A) support for multi-cores on the DSP side, each with their own
> 'trace' capability.
>
> B) support for other hardware platforms which may not have a DMA.
>
> C) support for 'probes' to retrieve and inject PCM data into specific
> firmware nodes.
>
> This patch does not create a new generic tracing infrastructure for
> Linux. We are exploring ways by which this standard tracing
> infrastructure can be used, we just haven't had time to look into it
> as we focused on runtime_pm and new platforms first.
>
> Also we need to make sure the DSP traces are not defined for Linux
> only, it's intended that the SOF firmware is used in non-Linux
> environments, so we want to use what Linux provides, but not constrain
> SOF to work for Linux only.
>
> Does this help?

OK, that's fine. Liam and I talked about Linux tracing for SOF, and I
thought this might be that. But this is rather a hardware data
logging, so it's a different beast.

thanks,

Takashi