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Message-ID: <08241854-2837-4e8b-ba12-79bcbc970c1b@linaro.org>
Date: Tue, 7 May 2024 08:27:18 +0200
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Subject: Re: path to landing patch to fix warm boot issue for qca6390
To: Wren Turkal <wt@penguintechs.org>, linux-bluetooth@vger.kernel.org
Cc: Zijun Hu <quic_zijuhu@quicinc.com>,
 Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
References: <3475f0dd-6a0f-4319-9590-379eee33f504@penguintechs.org>
From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
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In-Reply-To: <3475f0dd-6a0f-4319-9590-379eee33f504@penguintechs.org>
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On 06/05/2024 21:21, Wren Turkal wrote:
> Krzysztof,
> 
> I am reaching out to you as you had the most important objections to the 
> change to fix qca6390 for the warm boot/module reload bug that I am 
> experiencing.
> 
> For context, the problem is that the hci_uart module will send specific 
> vendor specfic commands during shutdown of the hardware under most 
> situations. These VSCs put the bluetooth device into a non-working state 
> on my Dell XPS 13 9310 with qca6390 bluetooth hardware.
> 
> Zijun's proposed fix is to not send these commands when it's not 
> appropriate for the hardware. The vendor commands should be avoided when 
> the hardware does not have persistent configuration or when the device 
> is in setup state (indicating that is has never been setup and should 
> not be sent the VSCs on the shutdown path). This is what Zijun's patch 
> implements.
> 
> In addition, Zijun's change removes the influence of both
> the QCA_BT_OFF qca flag and and HCI_RUNNING hdev flag. Zijun asserts 
> that those flags should not influence the sending of the VSCs in the 
> shutdown path. If I understand KK's objections properly, this is where 
> his objection is stemming from. KK, is this correct?

Yes, because this basically reverts my fix for shutdown path and
re-opens the race condition.

> 
> Zijun's proposed fix can be seen here: 
> https://patchwork.kernel.org/project/bluetooth/patch/1713932807-19619-3-git-send-email-quic_zijuhu@quicinc.com/
> 
> I'm wondering if we can resolve this impasse by splitting the change 
> into two changes, as follows:
> 
> 1. Change that removes the influence of the QCA_BT_OFF and HCI_RUNNING 
> flags in the shutdown path.

There was no explanation why this was removed, so it does not matter to
me whether this should be separate path or not.

Zijun, even though I asked four times, did not provide information on
which kernel this was prepared and tested, and on which hardware.

I assume Zijun did not understand original issue, thus assumes changing
the code to HCI_SETUP fixes it.


> 2. Add the quirk from Zijun's patch that fixes my hardward configuration.
> 
> I'm hoping that better clearer descriptions for #1 can help get that 
> landed since the logic current appears to be at odds with how the 
> hardware works.
> 
> Also, I am happy to split the patches into the two patches, or (maybe 
> more ideally) just modify the commit message to better indicate the 
> reason the change. I just need guidance from maintainers so that 
> whatever work I do leads to something acceptable for y'all.
> 
> So, please help me get this done. I am just a user with broken hardware 
> and a fondness for Linux. I would love to help do what's needed to get 
> this fix landed.

Best regards,
Krzysztof