linux-kernel - Re: [PATCH v1 1/2] staging: Introduce NVIDIA Tegra20 video decoder driver

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Message-ID: <20170928072308.s7npizjfnhkxh6zb@mwanda>
Date:   Thu, 28 Sep 2017 10:23:08 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>, linux-tegra@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v1 1/2] staging: Introduce NVIDIA Tegra20 video decoder
 driver

On Thu, Sep 28, 2017 at 02:28:04AM +0300, Dmitry Osipenko wrote:
> >> +	if (is_baseline_profile)
> >> +		frame->aux_paddr = 0xF4DEAD00;
> > 
> > The handling of is_baseline_profile is strange to me.  It feels like we
> > should always check it before we use ->aux_paddr but we don't ever do
> > that.
> > 
> 
> In a case of baseline profile, aux buffer isn't needed, HW should't use it. Aux
> phys address is set to a predefined and invalid address, so that in a case of
> VDE trying to use it, its invalid memory accesses would be reported in KMSG by
> memory controller driver and the reported invalid addresses would be known to be
> associated with the aux buffer. I'm not sure what you are meaning.

It's not used perhaps, but we do write it to the hardware, right?

	tegra_vde_write_iram_entry(iram_tables, 0, i, value, aux_paddr);

It's just strange.

regards,
dan carpenter