From: Sascha Hauer <s.hauer@pengutronix.de>
To: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH 2/6] ARM: introduce machine description
Date: Mon, 2 Dec 2013 12:54:09 +0100 [thread overview]
Message-ID: <20131202115409.GG24559@pengutronix.de> (raw)
In-Reply-To: <20131202110452.GC27628@ns203013.ovh.net>
On Mon, Dec 02, 2013 at 12:04:52PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 10:01 Mon 02 Dec , Sascha Hauer wrote:
> > > struct device_node *root;
> > > void *fdt;
> > > @@ -48,6 +49,10 @@ static int of_arm_init(void)
> > > }
> > >
> > > root = of_unflatten_dtb(NULL, fdt);
> > > +
> > > + if (arm_set_dt_machine(NULL))
> > > + pr_debug("No compatible machine found\n");
> >
> > Why call this with NULL and not the compatible string found in the just
> > unflattened dt?
>
> if NULL the code check for the compatible node
>
> otherwise for a specific compatible passs as arg
As said, it can't work when you call arm_set_dt_machine() before
of_set_root_node() as you do here.
> > > +int is_dt_compatible(const struct machine_desc *m, const char* dt_compat)
> > > +{
> > > + const char *const *dtc = m->dt_compat;
> > > +
> > > + while (dtc) {
*dtc btw. dtc will always be true, at least until it wraps around 32bit.
> > > + const char *s = *dtc;
> > > + if (dt_compat && !of_compat_cmp(s, dt_compat, strlen(dt_compat)))
> > > + return 1;
> > > + else if (of_machine_is_compatible(s))
> > > + return 1;
> > > + dtc++;
> > > + }
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +int arm_set_dt_machine(const char* dt_compat)
> >
> > I don't really understand how this function behaves. It should set the
> > machine desc based on dt_compat, but seems to fall back to some other
> > mechanism when dt_compat is NULL. Looking at it this function is only
>
> simple 2 case
>
> 1 check the compatible node
>
> 1 check a specific comp if pas as arg
>
> > called with NULL argument in your code, so it seems like it depends on
> > of_machine_is_compatible(), but this can only return something valid
> > when the root_node has been set. You call arm_set_dt_machine() before
> > of_set_root_node() so this can't work.
> >
> > Matching a machine_desc to a devicetree is more complicated. You can't
> > return the first match, but instead have to find the best match. If you
> > have multiple i.MX6 machines, then all will match to fsl,imx6. You have
> > to find the correct board though.
>
> no they will have their own compatible in the DT_MACHINE_DESC
Look for example in a current kernel. The SH Mobile koelsch board has:
compatible = "renesas,koelsch", "renesas,r8a7791";
The kernel has a specific koelsch machine descriptor:
> static const char * const koelsch_boards_compat_dt[] __initconst = {
> "renesas,koelsch",
> NULL,
> };
>
> DT_MACHINE_START(KOELSCH_DT, "koelsch")
> .smp = smp_ops(r8a7791_smp_ops),
> .init_early = r8a7791_init_early,
> .init_machine = koelsch_add_standard_devices,
> .init_time = rcar_gen2_timer_init,
> .dt_compat = koelsch_boards_compat_dt,
> MACHINE_END
Additionally there is a generic SoC machine descriptor:
> static const char *r8a7791_boards_compat_dt[] __initdata = {
> "renesas,r8a7791",
> NULL,
> };
>
> DT_MACHINE_START(R8A7791_DT, "Generic R8A7791 (Flattened Device Tree)")
> .smp = smp_ops(r8a7791_smp_ops),
> .init_early = r8a7791_init_early,
> .init_time = rcar_gen2_timer_init,
> .dt_compat = r8a7791_boards_compat_dt,
> MACHINE_END
Now of course when you have a koelsch board and koelsch support compiled
in you want to match the renesas,koelsch machine entry and not the
renesas,r8a7791 entry.
The kernel does this with of_flat_dt_match_machine().
Sascha
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next prev parent reply other threads:[~2013-12-02 11:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-28 18:05 [PATCH 0/6] ARM: machine struct support Jean-Christophe PLAGNIOL-VILLARD
2013-11-28 18:06 ` [PATCH 1/6] arm: gen-mach-types: add MAX_MACH_TYPE Jean-Christophe PLAGNIOL-VILLARD
2013-11-28 18:06 ` [PATCH 2/6] ARM: introduce machine description Jean-Christophe PLAGNIOL-VILLARD
2013-11-28 18:19 ` Alexander Aring
2013-11-28 19:00 ` Jean-Christophe PLAGNIOL-VILLARD
2013-11-28 19:02 ` Alexander Aring
2013-12-02 9:01 ` Sascha Hauer
2013-12-02 11:04 ` Jean-Christophe PLAGNIOL-VILLARD
2013-12-02 11:54 ` Sascha Hauer [this message]
2013-11-28 18:06 ` [PATCH 3/6] ARM: introduce SoC description Jean-Christophe PLAGNIOL-VILLARD
2013-11-28 18:06 ` [PATCH 4/6] AT91: detect SoC earlier Jean-Christophe PLAGNIOL-VILLARD
2013-11-28 18:06 ` [PATCH 5/6] AT91: switch to machine description Jean-Christophe PLAGNIOL-VILLARD
2013-11-28 18:06 ` [PATCH 6/6] vexpress: " Jean-Christophe PLAGNIOL-VILLARD
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