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From: Mathias Nyman <mathias.nyman@linux.intel.com>
To: Guan-Yu Lin <guanyulin@google.com>,
	Thinh.Nguyen@synopsys.com, gregkh@linuxfoundation.org,
	mathias.nyman@intel.com, stern@rowland.harvard.edu,
	yajun.deng@linux.dev, sumit.garg@linaro.org, kekrby@gmail.com,
	oneukum@suse.com, dianders@chromium.org, perex@perex.cz,
	tiwai@suse.com, niko.mauno@vaisala.com, andreyknvl@gmail.com,
	christophe.jaillet@wanadoo.fr, tj@kernel.org,
	stanley_chang@realtek.com, quic_jjohnson@quicinc.com,
	ricardo@marliere.net
Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-sound@vger.kernel.org, badhri@google.com,
	albertccwang@google.com, quic_wcheng@quicinc.com,
	pumahsu@google.com
Subject: Re: [PATCH v5 5/5] usb: host: enable sideband transfer during system sleep
Date: Mon, 14 Oct 2024 16:08:47 +0300	[thread overview]
Message-ID: <afc9fa53-b7f2-45d0-bd30-8681b71beef5@linux.intel.com> (raw)
In-Reply-To: <20241014085816.1401364-6-guanyulin@google.com>

On 14.10.2024 11.50, Guan-Yu Lin wrote:
> Sharing a USB controller with another entity via xhci-sideband driver
> creates power management complexities. To prevent the USB controller
> from being inadvertently deactivated while in use by the other entity, a
> usage-count based mechanism is implemented. This allows the system to
> manage power effectively, ensuring the controller remains available
> whenever needed.

I don't think all this is needed to prevent USB controller from being
deactivated while sideband is in use. The modified audio class driver
that uses sideband is still bound to a usb interface device, and all
normal pm reference counting should work.

To me it looks like this code is tricking pm framework into believing
the usb device and host controller have successfully suspended during
system suspend when they in reality are fully up and running.

I'm not sure I fully understand the case this series is solving.

Thanks
Mathias


  parent reply	other threads:[~2024-10-14 13:06 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-10-14  8:50 [PATCH v5 0/5] Support system sleep with offloaded usb transfers Guan-Yu Lin
2024-10-14  8:50 ` [PATCH v5 1/5] usb: dwc3: separate dev_pm_ops for each pm_event Guan-Yu Lin
2024-10-14  8:50 ` [PATCH v5 2/5] usb: xhci-plat: " Guan-Yu Lin
2024-10-14  8:50 ` [PATCH v5 3/5] usb: add apis for sideband usage tracking Guan-Yu Lin
2024-10-14  8:50 ` [PATCH v5 4/5] xhci: sideband: add api to trace sideband usage Guan-Yu Lin
2024-10-14  8:50 ` [PATCH v5 5/5] usb: host: enable sideband transfer during system sleep Guan-Yu Lin
2024-10-14  9:21   ` Greg KH
2024-10-14 16:06     ` Guan-Yu Lin
2024-10-14 13:08   ` Mathias Nyman [this message]
2024-10-14 16:19     ` Guan-Yu Lin
2024-10-14 15:56   ` Alan Stern
2024-10-14 15:59     ` Alan Stern
2024-10-15  3:56     ` Guan-Yu Lin
2024-10-15 14:43       ` Alan Stern
2024-10-16  7:40         ` Guan-Yu Lin
2024-10-16 14:45           ` Alan Stern
2024-10-18 11:59             ` Guan-Yu Lin
2024-10-18 14:41               ` Alan Stern

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