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Date:   Tue, 5 Jun 2018 15:07:58 -0600
From:   Rob Herring <robh@kernel.org>
To:     Vikash Garodia <vgarodia@codeaurora.org>
Cc:     hverkuil@xs4all.nl, mchehab@kernel.org, mark.rutland@arm.com,
        andy.gross@linaro.org, bjorn.andersson@linaro.org,
        stanimir.varbanov@linaro.org, linux-media@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        linux-soc@vger.kernel.org, devicetree@vger.kernel.org,
        acourbot@chromium.org
Subject: Re: [PATCH v2 5/5] venus: register separate driver for firmware
 device
Message-ID: <20180605210758.GA19888@rob-hp-laptop>
References: <1527884768-22392-1-git-send-email-vgarodia@codeaurora.org>
 <1527884768-22392-6-git-send-email-vgarodia@codeaurora.org>
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On Sat, Jun 02, 2018 at 01:56:08AM +0530, Vikash Garodia wrote:
> A separate child device is added for video firmware.
> This is needed to
> [1] configure the firmware context bank with the desired SID.
> [2] ensure that the iova for firmware region is from 0x0.
> 
> Signed-off-by: Vikash Garodia <vgarodia@codeaurora.org>
> ---
>  .../devicetree/bindings/media/qcom,venus.txt       |  8 +++-
>  drivers/media/platform/qcom/venus/core.c           | 48 +++++++++++++++++++---
>  drivers/media/platform/qcom/venus/firmware.c       | 20 ++++++++-
>  drivers/media/platform/qcom/venus/firmware.h       |  2 +
>  4 files changed, 71 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/media/qcom,venus.txt b/Documentation/devicetree/bindings/media/qcom,venus.txt
> index 00d0d1b..701cbe8 100644
> --- a/Documentation/devicetree/bindings/media/qcom,venus.txt
> +++ b/Documentation/devicetree/bindings/media/qcom,venus.txt
> @@ -53,7 +53,7 @@
>  
>  * Subnodes
>  The Venus video-codec node must contain two subnodes representing
> -video-decoder and video-encoder.
> +video-decoder and video-encoder, one optional firmware subnode.
>  
>  Every of video-encoder or video-decoder subnode should have:
>  
> @@ -79,6 +79,8 @@ Every of video-encoder or video-decoder subnode should have:
>  		    power domain which is responsible for collapsing
>  		    and restoring power to the subcore.
>  
> +The firmware sub node must contain the iommus specifiers for ARM9.
> +
>  * An Example
>  	video-codec@1d00000 {
>  		compatible = "qcom,msm8916-venus";
> @@ -105,4 +107,8 @@ Every of video-encoder or video-decoder subnode should have:
>  			clock-names = "core";
>  			power-domains = <&mmcc VENUS_CORE1_GDSC>;
>  		};
> +		venus-firmware {
> +			compatible = "qcom,venus-firmware-no-tz";
> +			iommus = <&apps_smmu 0x10b2 0x0>;

This mostly looks like you are adding a node in order to create a 
platform device. DT is not the only way to create platform devices and 
shouldn't be used when the device is not really a separate h/w device. 
Plus it seems like it is debatable that you even need a driver.

For iommus, just move it up to the parent (or add to existing prop).

Rob