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>,
	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: Thu, 1 Jul 2021 16:59:35 +0200	[thread overview]
Message-ID: <747df123-0aa0-7cb7-9fb3-f13c849894e5@redhat.com> (raw)
In-Reply-To: <20210701135949.GA51123@bjorn-Precision-5520>

On 7/1/21 3:59 PM, Bjorn Helgaas wrote:

[snip]

>> The IRQ handler is not called when unregistered, but it is called
>> when another handler for the shared IRQ is unregistered. In this
>> particular driver, both a "pcie-sys" and "pcie-client" handlers are
>> registered, then an error leads to "pcie-sys" being unregistered and
>> the handler for "pcie-client" being called.
> 
> Is this really true?  I think that would mean CONFIG_DEBUG_SHIRQ would
> not find this kind of bug unless we actually registered two or more
> handlers for the shared IRQ, but it's still a bug even only one
> handler is registered.
> 
> Looking at __free_irq() [1], my impression is that "action" is what
> we're removing and action->handler() is the IRQ handler we call when
> CONFIG_DEBUG_SHIRQ, so it doesn't look like it's calling the remaining
> handlers after removing one of them.
> 

Oh, you are completely right. I wrongly assumed that it was for the other
registered IRQ handlers but reading the source is clearly how you say it.

I now wonder why when debugging this I saw that the "pcie-client" handler
was called when "pcie-sys" was unregistered...

But anyways, you are correct and I'm OK with the text you shared.

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

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