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Date: Thu, 12 Oct 2017 18:43:32 +0300 From: Dmitry Osipenko <digetx@...il.com> To: Jon Hunter <jonathanh@...dia.com>, Thierry Reding <thierry.reding@...il.com> Cc: Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Rob Herring <robh+dt@...nel.org>, Mauro Carvalho Chehab <mchehab@...nel.org>, Stephen Warren <swarren@...dotorg.org>, Dan Carpenter <dan.carpenter@...cle.com>, linux-media@...r.kernel.org, linux-tegra@...r.kernel.org, devel@...verdev.osuosl.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v3 2/2] ARM: dts: tegra20: Add video decoder node On 12.10.2017 16:45, Jon Hunter wrote: > > On 12/10/17 14:25, Thierry Reding wrote: >> * PGP Signed by an unknown key >> >> On Thu, Oct 12, 2017 at 03:06:17PM +0300, Dmitry Osipenko wrote: >>> Hello Vladimir, >>> >>> On 12.10.2017 10:43, Vladimir Zapolskiy wrote: >>>> Hello Dmitry, >>>> >>>> On 10/11/2017 11:08 PM, Dmitry Osipenko wrote: >>>>> Add a device node for the video decoder engine found on Tegra20. >>>>> >>>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com> >>>>> --- >>>>> arch/arm/boot/dts/tegra20.dtsi | 17 +++++++++++++++++ >>>>> 1 file changed, 17 insertions(+) >>>>> >>>>> diff --git a/arch/arm/boot/dts/tegra20.dtsi b/arch/arm/boot/dts/tegra20.dtsi >>>>> index 7c85f97f72ea..1b5d54b6c0cb 100644 >>>>> --- a/arch/arm/boot/dts/tegra20.dtsi >>>>> +++ b/arch/arm/boot/dts/tegra20.dtsi >>>>> @@ -249,6 +249,23 @@ >>>>> */ >>>>> }; >>>>> >>>>> + vde@...1a000 { >>>>> + compatible = "nvidia,tegra20-vde"; >>>>> + reg = <0x6001a000 0x3D00 /* VDE registers */ >>>>> + 0x40000400 0x3FC00>; /* IRAM region */ >>>> >>>> this notation of a used region in IRAM is non-standard and potentially it >>>> may lead to conflicts for IRAM resource between users. >>>> >>>> My proposal is to add a valid device tree node to describe an IRAM region >>>> firstly, then reserve a subregion in it by using a new "iram" property. >>>> >>> >>> The defined in DT IRAM region used by VDE isn't exactly correct, actually it >>> should be much smaller. I don't know exactly what parts of IRAM VDE uses, for >>> now it is just safer to assign the rest of the IRAM region to VDE. >>> >>> I'm not sure whether it really worthy to use a dynamic allocator for a single >>> static allocation, but maybe it would come handy later.. Stephen / Jon / >>> Thierry, what do you think? >> >> This sounds like a good idea. I agree that this currently doesn't seem >> to be warranted, but consider what would happen if at some point we have >> more devices requiring access to the IRAM. Spreading individual reg >> properties all across the DT will make it very difficult to ensure they >> don't overlap. >> >> Presumably the mmio-sram driver will check that pool don't overlap. Or >> even if it doesn't it will make it a lot easier to verify because it's >> all in the same DT node and then consumers only reference it. >> >> I like Vladimir's proposal. I also suspect that Rob may want us to stick >> to a standardized way referencing such external memory. > > FWIW I agree. Seems like a nice approach and describes the h/w accurately. > Alright :)
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