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Message-ID: <1399774c-f188-81f1-4d15-367b9d0e4a59@linaro.org>
Date: Thu, 28 Apr 2022 12:00:14 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Marek Szyprowski <m.szyprowski@...sung.com>,
Lee Jones <lee.jones@...aro.org>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Alim Akhtar <alim.akhtar@...sung.com>,
Dinh Nguyen <dinguyen@...nel.org>,
Michal Simek <michal.simek@...inx.com>,
Liviu Dudau <liviu.dudau@....com>,
Sudeep Holla <sudeep.holla@....com>,
Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
Ray Jui <rjui@...adcom.com>,
Scott Branden <sbranden@...adcom.com>,
Broadcom Kernel Team <bcm-kernel-feedback-list@...adcom.com>,
Sylwester Nawrocki <s.nawrocki@...sung.com>,
devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Rob Herring <robh@...nel.org>
Subject: Re: [PATCH 08/10] ARM: dts: exynos: use proper
'dma-channels/requests' properties
On 28/04/2022 11:57, Marek Szyprowski wrote:
> 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@...nel.org>
>>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.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?
Hm, indeed, there is no point in this. Since they are read from
registers, what was the idea behind in commit 42cf20980cde?
Best regards,
Krzysztof
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