linux-kernel - RE: [PATCH 2/3] arm64: defconfig: Select CONFIG_RESET

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Message-ID: <DB3PR0402MB3916192607A09C7061740087F56E0@DB3PR0402MB3916.eurprd04.prod.outlook.com>
Date:   Mon, 29 Jun 2020 12:09:35 +0000
From:   Anson Huang <anson.huang@....com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Stefan Agner <stefan.agner@...adex.com>,
        "oleksandr.suvorov@...adex.com" <oleksandr.suvorov@...adex.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Leo Li <leoyang.li@....com>, Vinod Koul <vkoul@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Olof Johansson <olof@...om.net>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH 2/3] arm64: defconfig: Select CONFIG_RESET_IMX7 by default

Hi, Arnd


> Subject: Re: [PATCH 2/3] arm64: defconfig: Select CONFIG_RESET_IMX7 by
> default
> 
> On Mon, Jun 29, 2020 at 1:34 PM Anson Huang <anson.huang@....com>
> wrote:
> > > Subject: Re: [PATCH 2/3] arm64: defconfig: Select CONFIG_RESET_IMX7
> > > by default
> > >
> > > On Mon, Jun 29, 2020 at 12:25 PM Anson Huang
> <Anson.Huang@....com>
> > > wrote:
> > > >
> > > > i.MX7 reset driver now supports module build, it is no longer
> > > > built in by default, need to select it explicitly.
> > > >
> > > > Signed-off-by: Anson Huang <Anson.Huang@....com>
> > >
> > > Why not make it =m now that this is possible?
> >
> > It is because some drivers depends on this reset driver to work, such
> > as PCIe, If by default make it =m, it may impact PCIe's function,
> > adding module support at this point is try to provide function of
> > loadable module for Android, but don't want to impact any function which is
> working previously.
> 
> It sounds like your patch 1/3 is not ready to be merged then.
> 
> Please make sure that loading it later does not break other drivers that depend
> on it. Other drivers don't have to be able to deal with missing dependencies if
> this one is never loaded or disabled at compile-time. However before you
> make it possible to turn this into a loadable module, anything that depends on
> it must be able to deal with the modules getting loaded in a random order
> first.
> 
I searched all driver which uses this reset driver, looks like ONLY i.MX6 PCIe is using it and
it ONLY supports built-in, and inside this driver, it does NOT support defer probe etc.,
since I am NOT sure when this PCIe driver will add module support, so do you think if I
can make PCI_IMX6 select RESET_IMX7, then it won't break the PCIe function even
RESET_IMX7 is set to =m in defconfig, as when PCI_IMX6 is enabled as =y, RESET_IMX7 will
be also =y.

config PCI_IMX6
        bool "Freescale i.MX6/7/8 PCIe controller"
        depends on ARCH_MXC || COMPILE_TEST
        depends on PCI_MSI_IRQ_DOMAIN
        select PCIE_DW_HOST

Thanks,
Anson