netdev - Re: [PATCH v4 1/3] bus: mhi: host: add mhi_power_down_keep

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Message-ID: <20240301122559.GB2401@thinkpad>
Date: Fri, 1 Mar 2024 17:55:59 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Baochen Qiang <quic_bqiang@...cinc.com>
Cc: Kalle Valo <kvalo@...nel.org>,
	"Kalle Valo (QUIC)" <quic_kvalo@...cinc.com>,
	ath11k@...ts.infradead.org, linux-wireless@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, mhi@...ts.linux.dev,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH v4 1/3] bus: mhi: host: add mhi_power_down_keep_dev()

On Fri, Mar 01, 2024 at 10:04:06AM +0800, Baochen Qiang wrote:
> 
> 
> On 3/1/2024 3:35 AM, Kalle Valo wrote:
> > Baochen Qiang <quic_bqiang@...cinc.com> writes:
> > 
> > > On 2/29/2024 6:12 PM, Manivannan Sadhasivam wrote:
> > > > On Wed, Feb 28, 2024 at 10:22:41AM +0800, Baochen Qiang wrote:
> > > > > ath11k fails to resume:
> > > > > 
> > > > > ath11k_pci 0000:06:00.0: timeout while waiting for restart complete
> > > > > 
> > > > > This happens because when calling mhi_sync_power_up() the MHI subsystem
> > > > > eventually calls device_add() from mhi_create_devices() but the device
> > > > > creation is deferred:
> > > > > 
> > > > > mhi mhi0_IPCR: Driver qcom_mhi_qrtr force probe deferral
> > > > > 
> > > > > The reason for deferring device creation is explained in dpm_prepare():
> > > > > 
> > > > >           /*
> > > > >            * It is unsafe if probing of devices will happen during suspend or
> > > > >            * hibernation and system behavior will be unpredictable in this case.
> > > > >            * So, let's prohibit device's probing here and defer their probes
> > > > >            * instead. The normal behavior will be restored in dpm_complete().
> > > > >            */
> > > > > 
> > > > > Because the device probe is deferred, the qcom_mhi_qrtr_probe() is not
> > > > > called and thus MHI channels are not prepared:
> > > > > 
> > > > > So what this means that QRTR is not delivering messages and the QMI connection
> > > > > is not working between ath11k and the firmware, resulting a failure in firmware
> > > > > initialization.
> > > > > 
> > > > > To fix this add new function mhi_power_down_keep_dev() which doesn't destroy
> > > > > the devices for channels during power down. This way we avoid probe defer issue
> > > > > and finally can get ath11k hibernation working with the following patches.
> > > > > 
> > > > > Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.30
> > > > > 
> > > > > Signed-off-by: Kalle Valo <quic_kvalo@...cinc.com>
> > > > 
> > > > Did Kalle co-author this patch? If so, his Co-developed-by tag should
> > > > be added.
> > > 
> > > Hmm, I'm not sure...  I would like Kalle's thoughts on this.
> > 
> > IIRC I did only some simple cleanup before submitting the patch so I
> > don't think Co-developed-by is justified. I'm also fine with removing my
> > Signed-off-by.
> Thanks Kalle.
> 
> Hi Mani, so according to Kalle's comments, I'd like to keep the patch as is.
> 

No. Either remove his signed off by (as indicated by Kalle) or add a
co-developed-by tag. Keeping just a signed-off-by tag is wrong.

- Mani

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