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Message-ID: <033a82d5-b8c1-437c-be85-ea37fb1e9420@quicinc.com>
Date: Tue, 27 Feb 2024 18:52:33 +0800
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Subject: Re: [PATCH v3 0/3] wifi: ath11k: hibernation support
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To: <ath11k@lists.infradead.org>, <manivannan.sadhasivam@linaro.org>
CC: <linux-wireless@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
        <mhi@lists.linux.dev>
References: <20240227104427.7505-1-quic_bqiang@quicinc.com>
From: Baochen Qiang <quic_bqiang@quicinc.com>
In-Reply-To: <20240227104427.7505-1-quic_bqiang@quicinc.com>
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On 2/27/2024 6:44 PM, Baochen Qiang wrote:
> Currently in ath11k we keep the firmware running on the WLAN device when the
> network interface (wlan0) is down. The problem is that this will break
> hibernation, obviously the firmware can't be running after the whole system is
> powered off. To power down the ath11k firmware for suspend/hibernation some
> changes both in MHI subsystem and ath11k are needed.
> 
> This patchset fixes a longstanding bug report about broken hibernation support:
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=214649
> 
> There already is an RFC version which has been tested by multiple users with
> positive results:
> 
> https://patchwork.kernel.org/project/linux-wireless/cover/20231127162022.518834-1-kvalo@kernel.org/
> 
> Basically the RFC version adds two APIs to MHI stack: with the first one ath11k
> is able to keep MHI devices when going to suspend/hibernation, getting us rid of
> the probe deferral issue when resume back. while with the second one ath11k could
> manually prepare/unprepare MHI channels by itself, which is needed because QRTR
> doesn't probe those channels automatically in this case.
> 
> Mani, the MHI maintainer, firstly doesn't like that version and insists that an
> MHI device should be destroyed when suspend/hibernation, according to his
> understanding on device driver model. See
> 
> https://lore.kernel.org/mhi/20231127162022.518834-1-kvalo@kernel.org/
> 
> After a long discussion Mani thought we might need a new PM callback with which
> ath11k is able to wait until kernel unblocks device probe and thus MHI channels
> get probed. So we came to the kernel PM list and there Mani realized that his
> understanding is not correct so he finally agrees to keep MHI device during
> suspend/hibernation. See
> 
> https://lore.kernel.org/all/21cd2098-97e1-4947-a5bb-a97582902ead@quicinc.com/
> 
> Mani also pointed out that an MHI controller driver (ath11k here) should not touch
> MHI channels directly because those channels are managed by the corresponding MHI
> client driver (QRTR here). To address this, we come up with this version.
> 
> Compared with that RFC version, this version adds PM callbacks in QRTR module:
> suspend callback unprepares MHI channels during suspend and resume callback
> prepares those channels during resume. In this way ath11k doesn't need to do
> unprepare/prepare work by itself so those two APIs added in RFC version are
> removed now.
> 
> The power down/up procedure requires a specific sequence in which PM callbacks
> of wiphy, ath11k and QRTR are called, this is achieved by exploiting the
> child-father relationship between their device struct, and also the PM framework
> which separates whole suspend/resume process into several stages. Details in
> patch [3/3].
> 
> v3:
>   - skip QRTR suspend/resume if MHI device is found to be in suspend state.
Forget to mention that comments on 'destroy_device' are also updated per 
Mani in patch 1/3.

> 
> v2:
>   - add comment on why destroying the device is optional in
>     mhi_pm_disable_transition().
>   - rename mhi_power_down_no_destroy() as mhi_power_down_keep_dev().
>   - refine API description of mhi_power_down() and
>     mhi_power_down_keep_dev().
>   - add/remove __maybe_unused to QRTR PM callbacks.
>   - remove '#ifdef CONFIG_PM'.
>   - refine commit log of patch 1/3 and 2/3.
> 
> Baochen Qiang (3):
>    bus: mhi: host: add mhi_power_down_keep_dev()
>    net: qrtr: support suspend/hibernation
>    wifi: ath11k: support hibernation
> 
>   drivers/bus/mhi/host/internal.h        |   4 +-
>   drivers/bus/mhi/host/pm.c              |  42 ++++++++--
>   drivers/net/wireless/ath/ath11k/ahb.c  |   6 +-
>   drivers/net/wireless/ath/ath11k/core.c | 105 +++++++++++++++++--------
>   drivers/net/wireless/ath/ath11k/core.h |   6 +-
>   drivers/net/wireless/ath/ath11k/hif.h  |  14 +++-
>   drivers/net/wireless/ath/ath11k/mhi.c  |  12 ++-
>   drivers/net/wireless/ath/ath11k/mhi.h  |   5 +-
>   drivers/net/wireless/ath/ath11k/pci.c  |  44 +++++++++--
>   drivers/net/wireless/ath/ath11k/qmi.c  |   2 +-
>   include/linux/mhi.h                    |  18 ++++-
>   net/qrtr/mhi.c                         |  46 +++++++++++
>   12 files changed, 244 insertions(+), 60 deletions(-)
> 
> 
> base-commit: c39a5cfa0448f3afbee78373f16d87815a674f11