linux-kernel - Re: [PATCH] arm64: dts: rockchip: Correct GPIO polarity on brcm BT nodes

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Message-Id: <D4YVQCPZN9MJ.1TXHJU33TV5ZZ@cknow.org>
Date: Fri, 18 Oct 2024 13:02:21 +0200
From: "Diederik de Haas" <didi.debian@...ow.org>
To: "Krzysztof Kozlowski" <krzk@...nel.org>, "Heiko Stuebner"
 <heiko@...ech.de>, "Krzysztof Kozlowski" <krzk+dt@...nel.org>, "Rob
 Herring" <robh@...nel.org>, "Conor Dooley" <conor+dt@...nel.org>
Cc: <linux-rockchip@...ts.infradead.org>, "Samuel Holland"
 <samuel@...lland.org>, "Dragan Simic" <dsimic@...jaro.org>,
 <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
 <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] arm64: dts: rockchip: Correct GPIO polarity on brcm BT
 nodes

On Fri Oct 18, 2024 at 12:11 PM CEST, Krzysztof Kozlowski wrote:
> On 18/10/2024 11:22, Diederik de Haas wrote:
> > The GPIO polarity of the 'shutdown-gpios' property needs to be
> > ACTIVE_HIGH or the Bluetooth device won't work.
> > This also matches what other devices with the same BT device have.
>
> This should match the hardware.

Fair point.

The only documentation I have for the AzureWave-CM256SM is a datasheet.

Para "3.4 Power up Timing Sequence" of that datasheet has the following:

"The AW-CM256SM has two signals that enable or disable the Bluetooth
and WLAN circuits and the internal regulator blocks, allowing the host
to control power consumption."

WL_REG_ON:
"When this pin is high, the regulators are enabled and the WLAN section
is out of reset. When this pin is low, the WLAN section is in reset. If
BT_REG_ON and WL_REG_ON are both low, the regulators are disabled."

BT_REG_ON:
"If both BT_REG_ON and WL_REG_ON are low, the regulators will be
disabled. When this pin is low and WL_REG_ON is high, the BT section
is in reset."

>From that I conclude that BT_REG_ON needs to be high to get BT in a
working state.

But that datasheet is in its 19th revision, so can I assume that it now
is correct? (genuine question)

That's why I also looked at devices which uses the same hardware:
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/WHENCE?h=20241017#n2973
and those all had ACTIVE_HIGH for 'shutdown-gpios' in their hardware
description (ie DeviceTree) and if they were all broken, I think we
would've heard about it.

And my own testing showed it not working with ACTIVE_LOW and working
with ACTIVE_HIGH.
I just messed up my previous patch submission process, which this patch
is meant to correct.

> What if the Linux driver is just buggy?

Given the amount of 'spam' I get in `bluetoothctl` when it is working, I
think there's a real possibility that that is (also) the case.

Cheers,
  Diederik

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