From: Marc Zyngier <marc.zyngier@arm.com>
To: Kalle Valo <kvalo@codeaurora.org>
Cc: Amitkumar Karwar <amitkarwar@gmail.com>,
Enric Balletbo i Serra <enric.balletbo@collabora.com>,
Ganapathi Bhat <gbhat@marvell.com>,
Heiko Stuebner <heiko@sntech.de>,
Nishant Sarmukadam <nishants@marvell.com>,
Rob Herring <robh+dt@kernel.org>,
Xinming Hu <huxinming820@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org,
linux-wireless@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH 0/4] mwifiex PCI/wake-up interrupt fixes
Date: Fri, 8 Mar 2019 09:02:11 +0000 [thread overview]
Message-ID: <15c00f9e-58df-e885-f3b0-2c57e9fadb11@arm.com> (raw)
In-Reply-To: <87ef7hai0e.fsf@codeaurora.org>
On 08/03/2019 08:26, Kalle Valo wrote:
> Marc Zyngier <marc.zyngier@arm.com> writes:
>
>> For quite some time, I wondered why the PCI mwifiex device built in my
>> Chromebook was unable to use the good old legacy interrupts. But as MSIs
>> were working fine, I never really bothered investigating. I finally had a
>> look, and the result isn't very pretty.
>>
>> On this machine (rk3399-based kevin), the wake-up interrupt is described as
>> such:
>>
>> &pci_rootport {
>> mvl_wifi: wifi@0,0 {
>> compatible = "pci1b4b,2b42";
>> reg = <0x83010000 0x0 0x00000000 0x0 0x00100000
>> 0x83010000 0x0 0x00100000 0x0 0x00100000>;
>> interrupt-parent = <&gpio0>;
>> interrupts = <8 IRQ_TYPE_LEVEL_LOW>;
>> pinctrl-names = "default";
>> pinctrl-0 = <&wlan_host_wake_l>;
>> wakeup-source;
>> };
>> };
>>
>> Note how the interrupt is part of the properties directly attached to the
>> PCI node. And yet, this interrupt has nothing to do with a PCI legacy
>> interrupt, as it is attached to the wake-up widget that bypasses the PCIe RC
>> altogether (Yay for the broken design!). This is in total violation of the
>> IEEE Std 1275-1994 spec[1], which clearly documents that such interrupt
>> specifiers describe the PCI device interrupts, and must obey the
>> INT-{A,B,C,D} mapping. Oops!
>>
>> The net effect of the above is that Linux tries to do something vaguely
>> sensible, and uses the same interrupt for both the wake-up widget and the
>> PCI device. This doesn't work for two reasons: (1) the wake-up widget grabs
>> the interrupt in exclusive mode, and (2) the PCI interrupt is still routed
>> to the RC, leading to a screaming interrupt. This simply cannot work.
>>
>> To sort out this mess, we need to lift the confusion between the two
>> interrupts. This is done by extending the DT binding to allow the wake-up
>> interrupt to be described in a 'wake-up' subnode, sidestepping the issue
>> completely. On my Chromebook, it now looks like this:
>>
>> &pci_rootport {
>> mvl_wifi: wifi@0,0 {
>> compatible = "pci1b4b,2b42";
>> reg = <0x83010000 0x0 0x00000000 0x0 0x00100000
>> 0x83010000 0x0 0x00100000 0x0 0x00100000>;
>> pinctrl-names = "default";
>> pinctrl-0 = <&wlan_host_wake_l>;
>> wake-up {
>> interrupt-parent = <&gpio0>;
>> interrupts = <8 IRQ_TYPE_LEVEL_LOW>;
>> wakeup-source;
>> };
>> };
>> };
>>
>> The driver is then updated to look for this subnode first, and fallback to
>> the original, broken behaviour (spitting out a warning in the offending
>> configuration).
>>
>> For good measure, there are two additional patches:
>>
>> - The wake-up interrupt requesting is horribly racy, and could lead to
>> unpredictable behaviours. Let's fix that properly.
>>
>> - A final patch implementing the above transformation for the whole
>> RK3399-based Chromebook range, which all use the same broken
>> configuration.
>>
>> With all that, I finally have PCI legacy interrupts working with the mwifiex
>> driver on my Chromebook.
>>
>> [1] http://www.devicetree.org/open-firmware/bindings/pci/pci2_1.pdf
>>
>> Marc Zyngier (4):
>> dt-bindings/marvell-8xxx: Allow wake-up interrupt to be placed in a
>> separate node
>> mwifiex: Fetch wake-up interrupt from 'wake-up' subnode when it exists
>> mwifiex: Flag wake-up interrupt as IRQ_NOAUTOEN rather than disabling
>> it too late
>> arm64: dts: rockchip: gru: Move wifi wake-up interrupt into its own
>> subnode
>>
>> .../bindings/net/wireless/marvell-8xxx.txt | 23 ++++++++++++++++++-
>> .../dts/rockchip/rk3399-gru-chromebook.dtsi | 8 ++++---
>> drivers/net/wireless/marvell/mwifiex/main.c | 13 +++++++++--
>> 3 files changed, 38 insertions(+), 6 deletions(-)
>
> I didn't read the discussion in detail, but I understanding is that I
> should drop this series and wait for a new version. Please correct me if
> I misunderstood.
I indeed plan to resend the series with a slightly different approach,
removing support for the wake-up interrupt on mwifiex PCI devices
altogether.
Note that patch #3 is a fairly independent fix, which could be applied
right now.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2019-03-08 9:02 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-24 14:04 [PATCH 0/4] mwifiex PCI/wake-up interrupt fixes Marc Zyngier
2019-02-24 14:04 ` [PATCH 1/4] dt-bindings/marvell-8xxx: Allow wake-up interrupt to be placed in a separate node Marc Zyngier
2019-02-24 14:04 ` [PATCH 2/4] mwifiex: Fetch wake-up interrupt from 'wake-up' subnode when it exists Marc Zyngier
2019-02-24 14:04 ` [PATCH 3/4] mwifiex: Flag wake-up interrupt as IRQ_NOAUTOEN rather than disabling it too late Marc Zyngier
2019-02-26 23:31 ` Brian Norris
2019-02-26 23:34 ` Brian Norris
2019-04-04 10:22 ` Kalle Valo
2019-02-24 14:04 ` [PATCH 4/4] arm64: dts: rockchip: gru: Move wifi wake-up interrupt into its own subnode Marc Zyngier
2019-02-25 12:45 ` [PATCH 0/4] mwifiex PCI/wake-up interrupt fixes Ard Biesheuvel
2019-02-25 14:52 ` Marc Zyngier
2019-02-26 16:21 ` Ard Biesheuvel
2019-02-26 17:14 ` Marc Zyngier
2019-02-26 23:44 ` Brian Norris
2019-02-27 9:27 ` Marc Zyngier
2019-02-26 23:28 ` Brian Norris
2019-02-27 10:02 ` Marc Zyngier
2019-02-27 10:16 ` Ard Biesheuvel
2019-02-27 20:57 ` Brian Norris
2019-02-27 23:03 ` Rafael J. Wysocki
2019-02-28 2:29 ` Brian Norris
2019-02-28 11:03 ` Rafael J. Wysocki
2019-02-27 20:51 ` Brian Norris
2019-03-08 8:26 ` Kalle Valo
2019-03-08 9:02 ` Marc Zyngier [this message]
2019-03-08 9:36 ` Kalle Valo
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