Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <05c908ce-217f-6938-6745-7405ac39d8ea@samsung.com>
Date:   Thu, 28 Apr 2022 11:57:46 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0)
        Gecko/20100101 Thunderbird/91.8.0
Subject: Re: [PATCH 08/10] ARM: dts: exynos: use proper
 'dma-channels/requests' properties
Content-Language: en-US
To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        Lee Jones <lee.jones@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Dinh Nguyen <dinguyen@kernel.org>,
        Michal Simek <michal.simek@xilinx.com>,
        Liviu Dudau <liviu.dudau@arm.com>,
        Sudeep Holla <sudeep.holla@arm.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Ray Jui <rjui@broadcom.com>,
        Scott Branden <sbranden@broadcom.com>,
        Broadcom Kernel Team <bcm-kernel-feedback-list@broadcom.com>,
        Sylwester Nawrocki <s.nawrocki@samsung.com>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Rob Herring <robh@kernel.org>
From:   Marek Szyprowski <m.szyprowski@samsung.com>
In-Reply-To: <6981f93a-ef01-6ba0-4451-26526372d666@linaro.org>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain; charset="utf-8"
CMS-TYPE: 201P
References: <20220427155840.596535-1-krzysztof.kozlowski@linaro.org>
        <CGME20220427160347eucas1p23ce51e0fb49160d437961d98fd682c28@eucas1p2.samsung.com>
        <20220427155840.596535-9-krzysztof.kozlowski@linaro.org>
        <5eeac2a0-4293-675e-9dc2-25ed8ab3fb8f@samsung.com>
        <6981f93a-ef01-6ba0-4451-26526372d666@linaro.org>
Precedence: bulk

On 28.04.2022 11:54, Krzysztof Kozlowski wrote:
> On 28/04/2022 11:50, Marek Szyprowski wrote:
>> On 27.04.2022 17:58, Krzysztof Kozlowski wrote:
>>> pl330 DMA controller bindings documented 'dma-channels' and
>>> 'dma-requests' properties (without leading hash sign), so fix the DTS to
>>> match the bindings.
>>>
>>> Reported-by: Rob Herring <robh@kernel.org>
>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>> Are those properties really needed for PL330 driver on Exynos SoCs? I've
>> removed them and I still see the proper values read from registers and
>> reported in the log (Exynos4210):
>>
>> dma-pl330 12680000.dma-controller: Loaded driver for PL330 DMAC-141330
>> dma-pl330 12680000.dma-controller:       DBUFF-32x4bytes Num_Chans-8
>> Num_Peri-32 Num_Events-32
>> dma-pl330 12690000.dma-controller: Loaded driver for PL330 DMAC-141330
>> dma-pl330 12690000.dma-controller:       DBUFF-32x4bytes Num_Chans-8
>> Num_Peri-32 Num_Events-32
>> dma-pl330 12850000.dma-controller: Loaded driver for PL330 DMAC-141330
>> dma-pl330 12850000.dma-controller:       DBUFF-64x8bytes Num_Chans-8
>> Num_Peri-1 Num_Events-32
>>
>> I also don't see any code that would read those properties. IMHO they
>> should be simply removed at all, at least for the PL330 related nodes.
> In current Linux implementation they indeed are not used. Nothing parses
> them. However:
> 1. They describe (hopefully correct) the hardware.
> 2. They might be used by other implementations of pl330 driver.
>
> I would not remove them from existing sources, but indeed maybe there is
> no need to add for new files.

What's the point in having dt properties duplicating data that might be 
read from the driver registers?


Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland