linux-kernel - Re: [RFC PATCH v1 2/2] usb: host: add xhci-exynos to support Exynos SOCs

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Message-ID: <20221205023413.GD54922@ubuntu>
Date:   Mon, 5 Dec 2022 11:34:13 +0900
From:   Jung Daehwan <dh10.jung@...sung.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Colin Ian King <colin.i.king@...il.com>,
        Artur Bujdoso <artur.bujdoso@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Tomer Maimon <tmaimon77@...il.com>,
        "open list:USB SUBSYSTEM" <linux-usb@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:ARM/SAMSUNG S3C, S5P AND EXYNOS ARM ARCHITECTURES" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/SAMSUNG S3C, S5P AND EXYNOS ARM ARCHITECTURES" 
        <linux-samsung-soc@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>, sc.suh@...sung.com,
        taehyun.cho@...sung.com, jh0801.jung@...sung.com,
        eomji.oh@...sung.com
Subject: Re: [RFC PATCH v1 2/2] usb: host: add xhci-exynos to support Exynos
 SOCs

On Fri, Dec 02, 2022 at 01:23:56PM +0100, Krzysztof Kozlowski wrote:
> On 02/12/2022 13:22, Mathias Nyman wrote:
> > On 1.12.2022 11.01, Arnd Bergmann wrote:
> >> On Thu, Dec 1, 2022, at 09:06, Greg Kroah-Hartman wrote:
> >>> On Thu, Dec 01, 2022 at 11:13:31AM +0900, Daehwan Jung wrote:
> >>>> This driver works with xhci platform driver. It needs to override
> >>>> functions of xhci_plat_hc_driver. Wakelocks are used for sleep/wakeup
> >>>> scenario of system.
> >>>
> >>> So this means that no other platform xhci driver can be supported in the
> >>> same system at the same time.
> >>>
> >>> Which kind of makes sense as that's not anything a normal system would
> >>> have, BUT it feels very odd.  This whole idea of "override the platform
> >>> driver" feels fragile, why not make these just real platform drivers and
> >>> have the xhci platform code be a library that the other ones can use?
> >>> That way you have more control overall, right?
> > 
> > Agree that overriding the generic platform driver xhci_hc_platform_driver
> > from this exynos driver is odd.
> > 
> > But I don't understand how this works.
> > Where are the hcds created and added when this xhci-exonys driver binds to
> > the device? all this driver does in probe is the overriding?
> > 
> > Am I missing something here?
> 
> Because it is not a driver for Exynos... it's a driver for wakelocks for
> their specific Android use-cases which the manufacturer ships for their
> Android devices. Due to Google GKI, they try to squeeze into upstream.
> But this is huge misconception what should go to upstream and Samsung
> does not want to keep discussing. They just send random patches and
> disappear...
> 
> Best regards,
> Krzysztof
> 
> 

No. It's driver for Exynos. Currently It only has wakelocks but I will
submit one by one. Please think as the first patch of exynos not
squeezed.

Best Regards,
Jung Daehwan