Hello,
On 2016-02-15 18:52, Russell King - ARM Linux wrote:
On Wed, Feb 10, 2016 at 11:47:29AM +0100, Marek Szyprowski wrote:
From: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
Reading the periphid when the Primecell device is registered means that
the apb pclk must be available by then or the device won't be registered
at all.
By reading the periphid in amba_match() we can return -EPROBE_DEFER if
the apb pclk isn't there yet and the device will be retried later.
I've just realised, we can't do this. We need to read the peripheral
ID at registration time, because that's published to userspace via
(a) a sysfs attribute, and (b) as part of the uevent, which will be
used by udev to locate the driver module.
So, this will have the side effect of breaking systems which have
AMBA primecell devices configured as modules.
Sorry, I can't apply this. We can't regress existing platforms for
the sake of introducing new platforms to this code.
Then the only solution right now I see is to get back to v1:
http://lists.infradead.org/pipermail/linux-arm-kernel/2015-November/388199.html
which at least handles correctly device registration when power domain
driver
is available. You pointed that the patch cannot be applied, because failure
of dev_pm_domain_attach() will be fatal for device registration. Right now
lack of such call is fatal for the whole system, so there is really not a
big difference. Please also note that amba_get_enable_pclk() calls
clk_get(),
which also might return -EPROBE_DEFER, which already breaks device
registration the same way.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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