Hi Rob,
On Wed, Apr 8, 2015 at 3:40 PM, Rob Herring <[email protected]> wrote:
> On Wed, Apr 8, 2015 at 3:42 AM, Geert Uytterhoeven <[email protected]>
> wrote:
>> On Thu, Apr 2, 2015 at 4:38 AM, Grant Likely <[email protected]>
>> wrote:
>>> On Mon, 30 Mar 2015 15:27:27 +0200
>>> , Geert Uytterhoeven <[email protected]>
>>> wrote:
>>>> On Tue, Mar 24, 2015 at 6:56 PM, Pantelis Antoniou
>>>> <[email protected]> wrote:
>>>> >> On Mar 24, 2015, at 07:50 , Geert Uytterhoeven <[email protected]>
>>>> >> wrote:
>>>> >> IIUC, this would fix the issue I worked around in "ARM: shmobile:
>>>> >> r8a73a4:
>>>> >> Move pfc node to work around probe ordering bug"?
>>>> >> https://git.kernel.org/cgit/linux/kernel/git/horms/renesas.git/commit/?h=r8a73a4-ccf-and-multiplatform-for-v4.1&id=e4ba0a9bddff3ba52cec100414d2f178440efc91
>>
>>> There are two ways to fix this so that .dtb order doesn't matter. The
>>> dirty hack is to change the pfc driver to use subsys_initcall (level 4)
>>> or later so that it happens after the devices are registered. The second
>>
>> I've just tried that, and it doesn't work.
>>
>>> solution is to make the pfc drivers able to return -EPROBE_DEFER, but
>>> that also requires fixing deferred probe to start retrying devices
>>> before late_initcall time. Right now there is a holdoff flag that
>>
>> All the pfc driver can detect is that some platform_device.resource[i] are
>> empty (resource_type zero). Returning -EPROBE_DEFER won't help,
>> as the resource won't change later.
>>
>> The problem is not the initialization order of the device drivers, but the
>> creation order of the platform devices.
>>
>> of_device_alloc() silently (except for the pr_debug() message) ignores
>> any failures to setup IRQ resources. Hence platform devices for interrupt
>> providers must be created before platform devices for interrupt consumers,
>> which is what the reordering in DT fixes.
>
> This doesn't sound right. It ignores failures because platform_get_irq
> will parse the interrupts when called rather than just using the
> resource struct and will return EPROBE_DEFER if the irq resource is
> not ready. We left the of_device_alloc code in to be safe, but we
> should be able to remove it.
Thanks, using platform_get_irq() (and propagating EPROBE_DEFER) instead of
accessing the platform_device's resources directly indeed does work, but will
require some rework in the sh-pfc driver.
One more thing to consider for a "porting your driver to DT" tutorial ;-)
One side effect is that almost all drivers now end up being probe-deferred, as
the pinctrl configuration can't be done until the pfc driver is active.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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