From: Robin Murphy <robin.murphy@arm.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Javier Martinez Canillas <javierm@redhat.com>,
linux-kernel@vger.kernel.org,
Peter Robinson <pbrobinson@gmail.com>,
Shawn Lin <shawn.lin@rock-chips.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Heiko Stuebner <heiko@sntech.de>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Rob Herring <robh@kernel.org>,
linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org,
linux-rockchip@lists.infradead.org,
Michal Simek <michal.simek@xilinx.com>,
Ley Foon Tan <ley.foon.tan@intel.com>,
rfi@lists.rocketboards.org, Jingoo Han <jingoohan1@gmail.com>,
Thierry Reding <thierry.reding@gmail.com>,
Jonathan Hunter <jonathanh@nvidia.com>,
linux-tegra@vger.kernel.org
Subject: Re: [PATCH v2] PCI: rockchip: Avoid accessing PCIe registers with clocks gated
Date: Wed, 30 Jun 2021 10:44:44 +0100 [thread overview]
Message-ID: <fe0e75ba-6008-6dc0-e21e-4ea992bb6cdd@arm.com> (raw)
In-Reply-To: <20210629231410.GA4097899@bjorn-Precision-5520>
On 2021-06-30 00:14, Bjorn Helgaas wrote:
> On Tue, Jun 29, 2021 at 11:52:44AM +0100, Robin Murphy wrote:
>> On 2021-06-29 07:17, Javier Martinez Canillas wrote:
>>> On 6/29/21 2:38 AM, Bjorn Helgaas wrote:
>>>> On Thu, Jun 24, 2021 at 05:40:40PM -0500, Bjorn Helgaas wrote:
>>>
>>> [snip]
>>>
>>>>>>
>>>>>> So let's just move all the IRQ init before the pci_host_probe() call, that
>>>>>> will prevent issues like this and seems to be the correct thing to do too.
>>>>>
>>>>> Previously we registered rockchip_pcie_subsys_irq_handler() and
>>>>> rockchip_pcie_client_irq_handler() before the PCIe clocks were
>>>>> enabled. That's a problem because they depend on those clocks being
>>>>> enabled, and your patch fixes that.
>>>>>
>>>>> rockchip_pcie_legacy_int_handler() depends on rockchip->irq_domain,
>>>>> which isn't initialized until rockchip_pcie_init_irq_domain().
>>>>> Previously we registered rockchip_pcie_legacy_int_handler() as the
>>>>> handler for the "legacy" IRQ before rockchip_pcie_init_irq_domain().
>>>>>
>>>>> I think your patch *also* fixes that problem, right?
>>>>
>>>> The lack of consistency in how we use
>>>> irq_set_chained_handler_and_data() really bugs me.
>>>>
>>>> Your patch fixes the ordering issue where we installed
>>>> rockchip_pcie_legacy_int_handler() before initializing data
>>>> (rockchip->irq_domain) that it depends on.
>>>>
>>>> But AFAICT, rockchip still has the problem that we don't *unregister*
>>>> rockchip_pcie_legacy_int_handler() when the rockchip-pcie module is
>>>> removed. Doesn't this mean that if we unload the module, then receive
>>>> an interrupt from the device, we'll try to call a function that is no
>>>> longer present?
>>>
>>> Good question, I don't to be honest. I'll have to dig deeper on this but
>>> my experience is that the module removal (and device unbind) is not that
>>> well tested on ARM device drivers in general.
>>
>> Well, it does use devm_request_irq() so the handler should be unregistered
>> by devres *after* ->remove has finished, however that does still leave a
>> potential race window in which a pending IRQ could be taken during the later
>> part of rockchip_pcie_remove() after it has started turning off critical
>> things. Unless the clocks and regulators can also be delegated to devres, it
>> might be more robust to explicitly manage the IRQs as well. Mixing the two
>> schemes can be problematic when the exact order of both setup and teardown
>> matters.
>
> I don't understand the devm_request_irq() connection. I'm looking at
> this irq_set_chained_handler_and_data() call [1]:
>
> static int rockchip_pcie_setup_irq(struct rockchip_pcie *rockchip)
> {
> ...
> irq = platform_get_irq_byname(pdev, "legacy");
> irq_set_chained_handler_and_data(irq,
> rockchip_pcie_legacy_int_handler,
> rockchip);
>
> irq = platform_get_irq_byname(pdev, "client");
> ...
>
> We look up "irq", pass it to irq_set_chained_handler_and_data(), and
> throw it away without saving it anywhere. How would anything know how
> to unregister rockchip_pcie_legacy_int_handler()?
>
> I could imagine irq_set_chained_handler_and_data() saving what's
> needed for unregistration, but I would think that would require a
> device pointer, which we don't give it.
>
> I'm IRQ-illiterate, so please educate me!
Oh, my mistake, I was looking at the "sys" and "client" IRQs and spoke
too soon; the "legacy" IRQ does appear to be completely leaked as you
say, so there are two degrees of issue here.
Robin.
>
> Bjorn
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/pcie-rockchip-host.c?id=v5.13#n562
>
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next prev parent reply other threads:[~2021-06-30 9:47 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-08 8:04 [PATCH v2] PCI: rockchip: Avoid accessing PCIe registers with clocks gated Javier Martinez Canillas
2021-06-12 22:02 ` Peter Robinson
2021-06-22 10:31 ` Lorenzo Pieralisi
2021-06-24 21:57 ` Bjorn Helgaas
2021-06-24 23:18 ` Robin Murphy
2021-06-24 23:28 ` Bjorn Helgaas
2021-06-24 23:51 ` Robin Murphy
2021-06-24 22:40 ` Bjorn Helgaas
2021-06-25 7:09 ` Javier Martinez Canillas
2021-06-25 14:32 ` Bjorn Helgaas
2021-06-25 18:34 ` Javier Martinez Canillas
2021-06-29 0:38 ` Bjorn Helgaas
2021-06-29 6:17 ` Javier Martinez Canillas
2021-06-29 10:52 ` Robin Murphy
2021-06-29 23:14 ` Bjorn Helgaas
2021-06-30 9:44 ` Robin Murphy [this message]
2021-06-30 18:49 ` Bjorn Helgaas
2021-06-30 18:59 ` Bjorn Helgaas
2021-06-30 19:59 ` Javier Martinez Canillas
2021-06-30 20:30 ` Bjorn Helgaas
2021-06-30 20:46 ` Peter Robinson
2021-06-30 22:09 ` Javier Martinez Canillas
2021-07-01 13:59 ` Bjorn Helgaas
2021-07-01 14:59 ` Javier Martinez Canillas
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