Re: [PATCH v7 3/7] media: venus: Add support for AR50_LITE video core

[Bryan O'Donoghue]

On 17/07/2025 08:19, Jorge Ramirez wrote:
> > > --- a/drivers/media/platform/qcom/venus/helpers.c
> > > +++ b/drivers/media/platform/qcom/venus/helpers.c
> > > @@ -230,6 +230,24 @@ int venus_helper_alloc_dpb_bufs(struct venus_inst *inst)
> > >    }
> > >    EXPORT_SYMBOL_GPL(venus_helper_alloc_dpb_bufs);
> > > +void venus_helper_prepare_eos_data(struct venus_inst *inst,
> > > +				   struct hfi_frame_data *data)
> > > +{
> > > +	struct venus_core *core = inst->core;
> > > +
> > > +	data->buffer_type = HFI_BUFFER_INPUT;
> > > +	data->flags = HFI_BUFFERFLAG_EOS;
> > > +
> > > +	if (IS_V6(core) && is_fw_rev_or_older(core, 1, 0, 87))
> > > +		return;
> > > +
> > > +	if (IS_V4(core) && is_lite(core) && is_fw_rev_or_older(core, 6, 0, 53))
> > > +		data->alloc_len = 1;
> > > +
> > > +	data->device_addr = 0xdeadb000;
> > > +}
> > > +EXPORT_SYMBOL_GPL(venus_helper_prepare_eos_data);
> > This function doesn't appear to have alot to do with AR50_LITE as it
> > pertains to IS_V6() and IS_V4().
> >
> > This I think should be a separate patch with its own commit log to describe
> > the quite complex logic of version numbers going on here.
> Let me give it some background:
>
> According to the HFI specification, EOS (End-of-Stream) buffers must
> have 'valid' addresses. While the firmware currently appears to make no
> use of the EOS buffer contents, allocating and mapping them would have
> been a better driver choice IMO. Hoever this one has better performance
> which is probably the reason why it has stayed.
>
> The firmware then does perform operations involving the buffer's size
> and length fields, and enforces boundary checks accordingly. On the
> AR50_LITE platform, an earlier firmware version lacked a check on
> alloc_len, leading to a division-by-zero scenario.
>
> This has been addressed, and we plan to release firmware version 6.0.54,
> which includes the necessary boundary check for alloc_len.
>
> I should probaly replace IS_V4(core) && is_lite(core) with
> IS_AR50_LITE() instead of trying to give it the appearence of a design
> feature.
>
> seems the sensible thing to do, right?

I'll stipulate to all of that.

I know I'm being pedantic but, the title and subject of this patch is 
"AR50_LITE" does stuff.

As traveler from a mirror-universe - I would read the commit log here, 
look at this function and be none the wiser what was going on.

The EOS check is a fundamental HFI capability which is why I again 
reiterate it deserves its own commit log with the above explanation - 
word-for-word would be fine from my POV, to explain what is going on.

Long live the Empire!

---
bod