Re: [PATCH v2 1/2] dt-bindings: remoteproc: qcom: Add firmware bindings for Q6V5

[Sibi Sankar]

Hi Brian/Bjorn,
Thanks for the review!

On 2019-01-05 07:24, Brian Norris wrote:
> Hi again,
>
> On Thu, Jan 03, 2019 at 04:11:58PM -0800, Brian Norris wrote:
> > On Thu, Jan 03, 2019 at 04:01:45PM -0800, Bjorn Andersson wrote:
> > > I share your concern about this, but I came to suggest this as the
> > > driver cares about platforms but the firmware is (often?)
> > > device/product-specific.
> > >
> > > E.g. we will serve the MTP and Pixel 3 with the qcom,sdm845-adsp-pas
> > > compatible, but they are unlikely to run the same adsp firmware. This
> > > allows the individual dtb to specify which firmware the driver should
> > > use.
> >
> > I understand this, but that still doesn't mean we should be suggesting
> > each DTB to clutter the top-level firmware search path, especially 
> > since
> > lazy people will probably just use "modem.mdt" and similar. That means
> > you no longer can ship the same rootfs that supports both QCOM and
> > <other> modems, if <other> modem also uses the same lazy format.
> >
> > It seems like a much better practice to at least enforce a particular
> > prefix to things. e.g., the driver could assume:
> >
> >   qcom/sdm845-adsp-pas/ (or if you must, just qcom/)
> >
> > and your DTB only gets to add .../<your-string-here> to that path.
> >
> > In case it isn't clear: I think it's also severely misguided that the
> > existing driver gets away with lines like
> >
> > 	request_firmware(&fw, "modem.mdt", ...);
> >
> > today ;)
>
> To add to my thoughts, since I think maybe Sibi was a little unclear of
> my thoughts:
>
> One of my primary concerns with the existing approach is that it's
> basically a complete free-for-all. We should have some minimal 
> standards
> (enforced in code) such that our DTB can never point us at something
> like /lib/firmware/<other-vendor>/foo.bin (or /lib/firmware/modem.mdt;
> or lots of other bad examples). This could probably be done simply by
> always prefixing 'qcom/' (I don't remember -- does request_firmware()
> follow '..'? e.g., 'firmware-name = "../bar/foo.bin"'.)
>
> As a bonus: it would be very nice if we can provide a little more
> structure by default, and avoid arbitrary hierarchy in the DTS. That's
> where I brought up ath10k's "variant" as an example; if we can use
> 'compatible' to capture most of this particular Hexagon core's
> properties, then we only leave a single level of variability to the 
> DTS.
>
> But I might be off-base with the "bonus" paragraph. So I'd also be
> somewhat happy with something much less ambitious, like just a built-in
> prefix ('qcom/').
>
> And you can also just ignore my thoughts entirely (and I'll be even 
> less
> happy), since Rob did already provide his Reviewed-by ;) I mostly 
> wanted
> to give food for thought, in the hopes that something in here would 
> help
> improve this a bit.

Bjorn,
let me know how you want it implemented.
I am okay with either of the following:
* (variant tag based solution)
or
* (simply going ahead with what we have now).

> Regards,
> Brian

--
-- Sibi Sankar --
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