Re: [PATCH v2] PCI: rockchip: Avoid accessing PCIe registers with clocks gated

From: Javier Martinez Canillas <javierm@redhat.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: 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: Tue, 29 Jun 2021 08:17:03 +0200	[thread overview]
Message-ID: <2317a4bc-bd4d-53a7-7fa6-87728d5393cd@redhat.com> (raw)
In-Reply-To: <20210629003829.GA3978248@bjorn-Precision-5520>

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.

Best regards,
-- 
Javier Martinez Canillas
Software Engineer
New Platform Technologies Enablement team
RHEL Engineering