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

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Date:   Wed, 4 Mar 2020 23:23:33 +0530
From:   Anand Moon <linux.amoon@...il.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Linux USB Mailing List <linux-usb@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <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 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 0/3] Add support for suspend clk for Exynos5422 SoC

Hi Krzysztof,

On Wed, 4 Mar 2020 at 13:41, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> 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.
>
Ok

> 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...
>

Yep you are absolutely correct. Yes all the CLK_SLK* are call special clk's

Earlier I had share the FSYS clk diagram for Exynos5422
[0] https://imgur.com/gallery/zAiBoyh
from the diagram I mapped the naming terminology.

CLKMUX_USBDRD300 --->CLKDIV_USBDRD300 ---> SCLK_USBDRD300 (48 MHz)
---> USBDRD30_0 (SUSPEND_CLK)
                                   |
                                   |--->CLKDIV_USBPHY300--->
SCLK_USBPHY300 (48 MHZ) ---> USBDRD30_PHY_0 (USB30_SCLK_100M |
USB20_PICO_CLKCORE)

CLKMUX_USBDRD301 --->CLKDIV_USBDRD301 ---> SCLK_USBDRD301 (48 MHz)
---> USBDRD30_1 (SUSPEND_CLK)
                                   |
                                   |--->CLKDIV_USBPHY301--->
SCLK_USBPHY301 (48 MHZ) ---> USBDRD30_PHY_1 (USB30_SCLK_100M)

SCLK_USBDRD300      USBDRD30_0             operating clock to 24 MHz
SCLK_USBDRD301      USBDRD30_PHY_0    operating clock to 24 MHz
SCLK_USBPHY300      USBPHY30_0             operating clock to 24 MHz
SCLK_USBPHY301      USBDRD30_PHY_1    operating clock to 24 Mhz

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

I am trying to get the USB clk to get enabled for FSYS power domain
to working efficiently.

> 3. What is fixed with this patch?

Currently locally I tried to enable the FSYS power domain for USB 3.0 / USB 2.0.
but it's not working as expected, need future study.

*Note:* For now plz discard these patches.
When I get the FSYS power domain to work correctly.
I will link with those patch which will be better for testing.

-Anand

>
> Best regards,
> Krzysztof
>