Re: CONFIG_DEBUG_SHIRQ and PM
From: Ezequiel Garcia
Date: Wed Aug 26 2015 - 16:36:32 EST
On 26 August 2015 at 17:24, Felipe Balbi <balbi@xxxxxx> wrote:
>> static irqreturn_t tw68_irq(int irq, void *dev_id)
>> struct tw68_dev *dev = dev_id;
>> u32 status, orig;
>> int loop;
>> status = orig = tw_readl(TW68_INTSTAT) & dev->pci_irqmask;
> Now try to read that register when your clock is gated. That's the
> problem I'm talking about. Everything about the handler is functioning
> correctly; however clocks are gated in ->remove() and free_irq() is
> only called *AFTER* ->remove() has returned.
Yeah, it's pretty clear you are talking about clocks here. That's
why I said "read won't stall" in the next paragraph.
>> The IRQ handler accesses the device struct and then
>> reads through PCI. So if you use devm_request_irq
>> you need to make sure the device struct is still allocated
>> after remove(), and the PCI read won't stall or crash.
> dude, that's not the problem I'm talking about. I still have my
> private_data around, what I don't have is:
> _ _
> __ _ ___| | ___ ___| | __
> / _` | / __| |/ _ \ / __| |/ /
> | (_| | | (__| | (_) | (__| <
> \__,_| \___|_|\___/ \___|_|\_\
Yes, *you* may have your private data around and have a clock gated,
others (the tw68 for instance) may have its region released and unmapped.
And yet others may have $whatever resource released in the
remove() and assume it's available in the IRQ handler.
I honestly can't think why using request_irq / free_irq to solve this
is a workaround.
>> Interestingly, tw68 uses devm_request_irq with IRQF_SHARED :-)
>> Still, I don't think that's a good idea, since it relies on
>> the IRQ being freed *before* the device struct.
> that's not an issue at all. If you're using devm_request_irq() you're
> likely using devm_kzalloc() for the device struct anyway. Also, you
> called devm_kzalloc() before devm_request_irq() so IRQ *will* be freed
> before your private data; there's nothing wrong there.
Ezequiel GarcÃa, VanguardiaSur
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