linux-kernel - RE: [EXT] Re: [PATCH v3 4/4] soc: imx8m: change to use platform driver

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Message-ID: <AM6PR04MB6053E8B7B16148887482F7A4E2E00@AM6PR04MB6053.eurprd04.prod.outlook.com>
Date:   Thu, 19 Nov 2020 07:32:17 +0000
From:   Alice Guo <alice.guo@....com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>, Peng Fan <peng.fan@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [EXT] Re: [PATCH v3 4/4] soc: imx8m: change to use platform
 driver



> -----Original Message-----
> From: Krzysztof Kozlowski <krzk@...nel.org>
> Sent: 2020年11月18日 22:11
> To: Alice Guo <alice.guo@....com>
> Cc: robh+dt@...nel.org; shawnguo@...nel.org; s.hauer@...gutronix.de;
> dl-linux-imx <linux-imx@....com>; Peng Fan <peng.fan@....com>;
> devicetree@...r.kernel.org; linux-kernel@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org
> Subject: Re: [EXT] Re: [PATCH v3 4/4] soc: imx8m: change to use platform driver
> 
> Caution: EXT Email
> 
> On Wed, Nov 18, 2020 at 02:07:41PM +0000, Alice Guo wrote:
> >
> >
> > > -----Original Message-----
> > > From: Krzysztof Kozlowski <krzk@...nel.org>
> > > Sent: 2020年11月18日 18:42
> > > To: Alice Guo <alice.guo@....com>
> > > Cc: robh+dt@...nel.org; shawnguo@...nel.org; s.hauer@...gutronix.de;
> > > dl-linux-imx <linux-imx@....com>; Peng Fan <peng.fan@....com>;
> > > devicetree@...r.kernel.org; linux-kernel@...r.kernel.org;
> > > linux-arm-kernel@...ts.infradead.org
> > > Subject: Re: [EXT] Re: [PATCH v3 4/4] soc: imx8m: change to use
> > > platform driver
> > >
> > > Caution: EXT Email
> > >
> > > On Wed, Nov 18, 2020 at 10:28:47AM +0000, Alice Guo wrote:
> > >  >
> > > > > If it is properly explained and there is no other way then yes,
> > > > > you could. Here, for old DTBs, I would prefer to use
> > > > > of_platform_device_create() and bind to "soc" node (child of root).
> > > > > This way you would always have device and exactly one entry
> > > > > point for the probe.
> > > > >
> > > >
> > > > static struct platform_driver imx8_soc_init_driver = {
> > > >       .probe = imx8_soc_init_probe,
> > > >       .driver = {
> > > >               .name = "soc@0",
> > > >       },
> > > > };
> > > > Can I use "soc@0" to match this driver? It will not use
> > > > of_platform_device_create(). It will use of_find_property() to
> > > > determine whether and nvmem-cells can be used. If there is no
> > > > nvmem-cells,
> > > it will use the old way, which supports old DTBS. There is no need
> > > to add new compatible.
> > >
> > > No, the soc@0 is not a proper name for the driver.
> >
> > I have no good idea, please give suggestion. Should I still add new compatible?
> > Should I still keep device_initcall? If use
> > of_platform_device_create(), which node should I use?
> 
> I mentioned my idea in the email before - of_platform_device_create() to bind
> to the soc node. This will have to be in the initcall, you don't have a choice to
> avoid it, since there was no compatible before.
>

	node = of_find_node_by_path("/soc@0");
	if (!node)
		return -ENODEV;

	pdev = of_platform_device_create(node, "XXX", NULL);
	if (!pdev)
		return -ENODEV;

Cannot use of_platform_device_create because "of_node_test_and_set_flag(np, OF_POPULATED)" returns true.
of_platform_device_create is used to create platform device, but soc@0 is created by common code. I don't know how
to bind to the soc node. The way I did in v3 seems not bad, it can work correctly and support old DTBs. Can I keep this way?

Best regards,
Alice Guo

> Best regards,
> Krzysztof