linux-kernel - Re: [PATCH v7 3/7] media: venus: Add support for AR50

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Message-ID: <aHjtgHT2Nxmm5nEf@trex>
Date: Thu, 17 Jul 2025 14:33:04 +0200
From: Jorge Ramirez <jorge.ramirez@....qualcomm.com>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Cc: Jorge Ramirez <jorge.ramirez@....qualcomm.com>, quic_vgarodia@...cinc.com,
        quic_dikshita@...cinc.com, krzk+dt@...nel.org, konradybcio@...nel.org,
        mchehab@...nel.org, andersson@...nel.org, conor+dt@...nel.org,
        amit.kucheria@....qualcomm.com, linux-media@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 3/7] media: venus: Add support for AR50_LITE video core

On 17/07/25 10:29:44, Bryan O'Donoghue wrote:
> 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.

right this is because I think you saw through my inconsistency.

The truth is I should have written the function as below; and I think
now there is a case for it being in this patch since it is addressing a
firmware issue on the firmware release supporting this core which the
patch is adding the functionality for.

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_AR50_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);

what do you think? this is really just adding a the AR50_LITE line to
the existing implementation.

> 
> 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.
>

umm not sure yet but if the above does not make you change your mind
I'll do it.

> Long live the Empire!

:)

> 
> ---
> bod