From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH v3 2/2] ARM: dts: tegra20: Add video decoder node Date: Thu, 12 Oct 2017 14:45:08 +0100 Message-ID: <485a1192-8ef2-5ae1-a45f-d9b7167d8241@nvidia.com> References: <0b6150a7-5b2b-ca4d-eb34-b6614e4833df@mentor.com> <81f39096-dc66-c98b-50f6-fc81ee1804ec@gmail.com> <20171012132543.GB4453@ulmo> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20171012132543.GB4453@ulmo> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" To: Thierry Reding , Dmitry Osipenko Cc: devel@driverdev.osuosl.org, devicetree@vger.kernel.org, Stephen Warren , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Rob Herring , Vladimir Zapolskiy , linux-tegra@vger.kernel.org, Mauro Carvalho Chehab , Dan Carpenter , linux-media@vger.kernel.org List-Id: linux-tegra@vger.kernel.org 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 >>>> --- >>>> 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@6001a000 { >>>> + 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. Cheers Jon -- nvpublic