linux-kernel - Re: [PATCHv2 0/3] Add support for suspend clk for Exynos5422 SoC

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Date:   Wed, 4 Mar 2020 09:11:51 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Anand Moon <linux.amoon@...il.com>
Cc:     linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Felipe Balbi <balbi@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 0/3] Add support for suspend clk for Exynos5422 SoC

On Sun, Mar 01, 2020 at 09:20:15PM +0000, Anand Moon wrote:
> Seried build and tested on linux next-20200228.
> 
> This patch series tries to enable suspend clk using
> exynos dwc3 driver, for this I have added new
> compatible string "samsung,exynos5420-dwusb3"
> so that we could add new suspend clk in addition
> to the core clk. exynos dwc3 driver will help
> enable/disable these clk.

That's not entirely correct. You enable there SCLK which is a "special
clock", not a "suspend clock". You use word "suspend: in multiple places
in commits making an impression that it is about some suspend clock...
no, there is no suspend clock.

There is however a clock which driver calls suspend_clk (but it is just
some name) and it is being enabled for entire lifetime of device (so
also during suspend). AFAIU, this is not needed for Exynos5422 but I am
not sure. So please convince me...

However I have still the same questions:
1. What problem are you trying to solve here?
2. Why this is needed?
3. What is fixed with this patch?

Best regards,
Krzysztof

> 
> This series PatchV2.
> --Added the clk names for exynos5420 compatible.
> --Added missing support for Exyno5410 SoC suspend clock.
> --Update the commit message to support suspend clk usages.
> 
> ---
> Long time ago I tried to add suspend clk for dwc3 phy
> which was wrong appoch, see below.
> 
> [0] https://lore.kernel.org/patchwork/patch/837635/
> [1] https://lore.kernel.org/patchwork/patch/837636/
> 
> Previous changes V3 (It was send with wrong Patch version)
> [2] https://patchwork.kernel.org/cover/11373043/
> 
> -Anand
> 
> Anand Moon (3):
>   devicetree: bindings: exynos: Add new compatible for Exynos5420 dwc3
>     clocks support
>   ARM: dts: exynos: Add missing usbdrd3 suspend clk
>   usb: dwc3: exynos: Add support for Exynos5422 suspend clk
> 
>  Documentation/devicetree/bindings/usb/exynos-usb.txt | 5 ++++-
>  arch/arm/boot/dts/exynos5410.dtsi                    | 8 ++++----
>  arch/arm/boot/dts/exynos5420.dtsi                    | 8 ++++----
>  arch/arm/boot/dts/exynos54xx.dtsi                    | 4 ++--
>  drivers/usb/dwc3/dwc3-exynos.c                       | 9 +++++++++
>  5 files changed, 23 insertions(+), 11 deletions(-)
> 
> -- 
> 2.25.1
>