From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Sergey Shtylyov <s.shtylyov@omp.ru>
Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org,
Hans de Goede <hdegoede@redhat.com>, Jens Axboe <axboe@kernel.dk>,
Damien Le Moal <damien.lemoal@opensource.wdc.com>
Subject: Re: [PATCH v1 1/2] ata: libahci_platform: Get rid of dup message when IRQ can't be retrieved
Date: Fri, 10 Dec 2021 19:51:35 +0200 [thread overview]
Message-ID: <YbOTp2f0WLhPo0bu@smile.fi.intel.com> (raw)
In-Reply-To: <51c0aa6e-e75f-faa7-b9b1-850684da58c8@omp.ru>
On Fri, Dec 10, 2021 at 08:39:38PM +0300, Sergey Shtylyov wrote:
> On 12/10/21 2:28 PM, Andy Shevchenko wrote:
>
> >>>>>>>>> While at it, drop redundant check for 0 as platform_get_irq() spills
> >>>>>>>>> out a big WARN() in such case.
> >>>>>>>>
> >>>>>>>> And? IRQ0 is still returned! :-(
> >>>>>>>
> >>>>>>> It should not be returned in the first place.
> >>>>>>
> >>>>>> But it still is, despite the WARN(), right?
> >>>>>
> >>>>> So, you admit that there is a code which does that?
> >>>>
> >>>> I admit *what*?! That platfrom_get_irq() and its ilk return IRQ0 while they
> >>>> shouldn't? =)
> >>>
> >>> That there is a code beneath platform_get_irq() that returns 0, yes.
> >>
> >> Look at the ACPI-specific GpioInt handling code (just above the out_not_found label) --
> >> I'm not sure the check there is correct -- I'm not very familiar with ACPI, you seem to
> >> know it much better. :-)
> >
> > And what is your point here exactly?
>
> You're saying IRQ0 shouldn't be returned (by the ACPI code) -- from this fragment
> we can see that it may be returned...
Please, provide your analysis, I really don't see how it's possible.
If you prove that, we must fix the severe bug then.
> > If == 0 case happens, it will be
> > immediately WARN() and reported (I hope)
>
> Well, "hope dies last"... :-)
Believe, big WARNs are quite likely to be reported if not by humans, then by
CIs and fuzzers. So, the hope is rather to word 'immediately'.
> > since it will mean bug in the code.
> >
> >> Also, 0 can be specified via the normal IRQ resource. I know of e.g. the Alchemy MIPS SoCs
> >> that have IRQ0 used by UART0; luckily, currently SoC IRQs are mapped starting at Linux IRQ8
> >> (but it wasn't the case in the 2.6.1x time frame where we had issue with the serial driver)...
> >
> > You mixed up HW IRQ with vIRQ.
>
> I didn't. Linux expects the vIRQs (I called them Linux IRQs). In the 2.6.1x time frame
> those corresponded 1:1 on Alchemy. Also, there's 8259 which is always mapped at vIRQ0 (or
> the legacy drivers won't work).
>
> > The former one may be 0 and it's completely valid case, while
> > the second one is not.
>
> Well, request_irq() happilly takes vIRQ0. Moreover, there are 8253 drivers in e.g. the arch/x86/
> (PPC and MIPS too) which do use vIRQ0.
This is an exception which is not in the scope here. Let me remind that the
topic here is libahci_platform and platform_get_irq().
> >>>>> That code should be fixed first. Have you sent a patch?
> >>>>
> >>>> Which code?! You got me totally muddled. =)
> >>>
> >>> Above mentioned.
> >>
> >> What needs to be fixed in this case is the interrupt controller driver.
> >
> > What do you mean by that?
>
> You better ask Linus... ;-)
If you cite somebody you have to understand what they said, right?
Lemme repeat the question, what do you mean by that? In your own words, please.
> > vIRQ is handled by IRQ core, IRQ controller driver
> > just a mere provider of the resource. And those exceptions for vIRQ == 0
> > shouldn't be propagated to the platform code or so.
>
> >> Quoting Linus
> >> (imprecisely :-)), IRQ #s should be either mapped starting with #1 or IRQ0 remapped at
> >> the end of the controller's interrupt range... I currently have no information on the
> >> platforms requiring such kind of fixing (Alchemy don't seem to need it now)...
>
> Well, actually that Linus' quote predates drivers/irqchip/, so I must confess this
> argument was wrong... :-)
>
> > Again, do not mix vIRQ (about which Linus ranted) and HW IRQ.
...
> >>>>>>>>> - if (!irq)
> >>>>>>>>> - return -EINVAL;
> >>>>>>>>
> >>>>>>>> This is prermature -- let's wait till my patch that stops returning IRQ0 from
> >>>>>>>> platform_get_irq() and friends gets merged....
> >>>>>>>
> >>>>>>> What patch?
> >>>>>>
> >>>>>> https://marc.info/?l=linux-kernel&m=163623041902285
> >>>>>>
> >>>>>>> Does it fix platform_get_irq_optional()?
> >>>>>>
> >>>>>> Of course! :-)
> >>>>>
> >>>>> Can you share link to lore.kernel.org, please?
> >>>>> It will make much easier to try and comment.
> >>>>
> >>>> I don't know how to uise it yet, and I'm a little busy with other IRQ0 issues ATM,
> >
> >> A little bit, I meant to type.
> >
> > No problem. I just haven't got what other IRQ0 issues except fixing
> > platform_get_irq_optional() et al. could be possibly needed...
>
> There is other IRQ0 issue which is very old already...
Is it big secret? What is that issue?
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2021-12-10 17:52 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-09 14:59 [PATCH v1 1/2] ata: libahci_platform: Get rid of dup message when IRQ can't be retrieved Andy Shevchenko
2021-12-09 14:59 ` [PATCH v1 2/2] ata: libahci_platform: Remove bogus 32-bit DMA mask attempt Andy Shevchenko
2021-12-10 19:34 ` Andy Shevchenko
2021-12-11 0:04 ` Damien Le Moal
2021-12-17 0:58 ` Damien Le Moal
2021-12-17 11:57 ` Andy Shevchenko
2021-12-09 15:21 ` [PATCH v1 1/2] ata: libahci_platform: Get rid of dup message when IRQ can't be retrieved Hans de Goede
2021-12-09 17:24 ` Sergey Shtylyov
2021-12-09 17:42 ` Andy Shevchenko
2021-12-09 18:22 ` Sergey Shtylyov
2021-12-09 19:22 ` Andy Shevchenko
2021-12-09 19:27 ` Andy Shevchenko
2021-12-09 20:31 ` Sergey Shtylyov
2021-12-09 20:29 ` Sergey Shtylyov
2021-12-10 10:44 ` Andy Shevchenko
2021-12-10 11:14 ` Sergey Shtylyov
2021-12-10 11:28 ` Andy Shevchenko
2021-12-10 17:39 ` Sergey Shtylyov
2021-12-10 17:51 ` Andy Shevchenko [this message]
2021-12-09 22:49 ` Damien Le Moal
2021-12-09 22:57 ` Damien Le Moal
2021-12-10 8:47 ` Andy Shevchenko
2021-12-10 16:38 ` Sergey Shtylyov
2021-12-10 17:57 ` Andy Shevchenko
2021-12-10 8:59 ` Sergey Shtylyov
2021-12-10 10:46 ` Andy Shevchenko
2021-12-10 11:19 ` Sergey Shtylyov
2021-12-10 11:36 ` Andy Shevchenko
2021-12-10 17:15 ` Sergei Shtylyov
2021-12-10 17:59 ` Andy Shevchenko
2021-12-10 19:01 ` Sergey Shtylyov
2021-12-10 19:25 ` Andy Shevchenko
2021-12-10 19:30 ` Sergey Shtylyov
2021-12-10 19:35 ` Sergei Shtylyov
2021-12-11 10:13 ` Sergey Shtylyov
2021-12-13 11:26 ` Andy Shevchenko
2021-12-10 23:45 ` Damien Le Moal
2021-12-11 10:25 ` Sergey Shtylyov
2021-12-12 22:39 ` Damien Le Moal
2021-12-13 11:52 ` Andy Shevchenko
2021-12-13 21:36 ` Damien Le Moal
2021-12-13 22:02 ` Andy Shevchenko
2021-12-13 11:49 ` Andy Shevchenko
2021-12-13 11:46 ` Andy Shevchenko
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