[5/7] arm64: ARMv8 RTSM model (SoC) support

From: Pawel Moll <pawel.moll@arm.com>

On Tue, 2012-12-11 at 16:39 +0000, Catalin Marinas wrote:
> > > diff --git a/arch/arm6
> > > +static const char *vexpress_dt_match[] __initdata = {
> > > +       "arm,vexpress",
> > > +       NULL,
> > > +};
> > > +
> > > +static int __init vexpress_init(void)
> > > +{
> > > +       if (!of_flat_dt_match(of_get_flat_dt_root(), vexpress_dt_match))
> > > +               return 0;
> > > +
> > > +       vexpress_sysreg_of_early_init();
> > > +       vexpress_clk_of_init();
> > > +
> > > +       return 0;
> > > +}
> > > +arch_initcall(vexpress_init);
> > 
> > I think it would be more appropriate for these two to check the presence of
> > the individual devices, and move the caller into the actual device driver,
> > rather than checking for the root node of the device tree.
> > 
> > There may be cases where we want to check the root node, but both the clock
> > setup and the sysreg should both be detectable.
> 
> I cc'ed Pawel as well since it's touching his code. We've been through
> several versions internally and didn't find a clear winner. Currently,
> vexpress_clk_of_init() requires vexpress_sysreg_of_early_init() to be
> called first. Pawel has a patch to allow sysreg self-initialisation when
> called from vexpress_clk_of_init().
> 
> This leaves us with a way to call vexpress_clk_of_init() directly from
> clk-vexpress.c. There are two ways:
> 
> 1. arch_initcall() in clk-vexpress.c, checking for the DT match.
> 2. driver registration (arch_initcall) and later probing when
>    of_platform_populate() is called from the arch/arm64 code.
> 
> The 2nd option above relies on the DT order since the clocks must be
> registered before any AMBA device is registered, so I'm not too keen.
> This leaves us with option 1 or any other suggestion you may have.

The idea I had was to associate the root of the device tree with the
"platform" device, see below. This makes it possible to write a platform
driver for the particular platform, so the code for the vexpress could
look more or less like this...

static int __devinit vexpress_probe(struct platform_device *dev)
{
        vexpress_sysreg_of_early_init();
        vexpress_clk_of_init();

        of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL);

        return 0;
}

static const struct of_device_id vexpress_match[] = {
        { .compatible = "arm,vexpress", },
        {}
};

static struct platform_driver vexpress_driver = {
        .driver = {
                .name = "vexpress",
                .of_match_table = vexpress_match,
        },
        .probe = vexpress_probe,
};

static int __init vexpress_init(void)
{
        return platform_driver_register(&vexpress_driver);
}
arch_initcall(vexpress_init);

... and live, for example, in drivers/platforms/vexpress.c. I think it
would neatly fit the device model - a platform driver for the "platform"
platform device ;-)

Pawe?

8<---------------------------
From a19b22ed4d5042a2249f0aa41633cbbc7310d5f3 Mon Sep 17 00:00:00 2001
From: Pawel Moll <pawel.moll@arm.com>
Date: Mon, 26 Nov 2012 12:35:10 +0000
Subject: [PATCH] platform: Make platform_bus device a platform device

... describing the root of the device tree, so one can write
a platform driver initializing the platform.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>
---
 arch/arm/mach-imx/devices/devices.c |    4 ++--
 arch/unicore32/kernel/puv3-core.c   |    2 +-
 arch/unicore32/kernel/puv3-nb0916.c |    6 +++---
 drivers/base/platform.c             |   18 ++++++++++++------
 drivers/char/tile-srom.c            |    2 +-
 drivers/mmc/host/sdhci-pltfm.c      |    2 +-
 drivers/scsi/hosts.c                |    2 +-
 include/linux/platform_device.h     |    2 +-
 8 files changed, 22 insertions(+), 16 deletions(-)

[5/7] arm64: ARMv8 RTSM model (SoC) support

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