From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 799FA3CF40; Mon, 22 Jan 2024 13:09:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705928995; cv=none; b=gTHvRPvSYljyQvOX+oKJXGpTeHkIRRXhONkmYG4cyEj9LeLZ2DIWdRdbow7HhjAt1AON9MQBzv2sz0Tw/U+iXXdIs9at7tdFJNxJea2m3l238JHGtHHNTGxVtCd5/ozhK/NH6ZKFwYyHKWiLWmKxODieOLRZ2wuFaCzz5beZoIw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705928995; c=relaxed/simple; bh=M8QIjfgLmhjPzTCa+15a6GOuMApXegCXdUQZ/H5k2DU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=P/YdYCgo487wROAyxnogWsLCmYxcC/zPv988+SBX8AaiDvyIVoYIIftyPrANTUSQD7bgIf4pAETT9TNBodWuU9Nex35P+FXguF13nXiyeoEJ09wk98MJNIT+efVdVzj4ExuRlX04MTTg6XKokVscfyg+rqQdlAvPuXvPzoCU+Nk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qDK2yH+I; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qDK2yH+I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C3BABC433C7; Mon, 22 Jan 2024 13:09:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1705928994; bh=M8QIjfgLmhjPzTCa+15a6GOuMApXegCXdUQZ/H5k2DU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qDK2yH+IyNUI5eeCq14hsHsWxNiGiPh+F+iDqLLBTHHz39Q3M7fBTIE1/AQsAJXv1 zFA4KyEah/qF/IxvCI/dddIZaCdAZVjCWkbSnsO8W2K2uAbEe1AEEjGv/nkHWAnVuC guI0pYz1v+TEcowjwVTzbTxrfK1H9L/dKS9w6jypNFQlRXdmEMqlwrBCy8U5WctNRW hIcWRdmUn2ZqLaWLkpr9NHeXcrhd9axnEVMx9sywyzitz/8rfdXrq2DAcSy/8fKwn8 4KePO05Bpr6NUDQVRryRFGhBiYy72nd697/K5UooqWFOnVBuBV7GaRXdg/rVxvAO0w rjNvkxxr36s8Q== Date: Mon, 22 Jan 2024 18:39:47 +0530 From: Manivannan Sadhasivam To: Baochen Qiang Cc: Manivannan Sadhasivam , Kalle Valo , mhi@lists.linux.dev, ath11k@lists.infradead.org, linux-wireless@vger.kernel.org, quic_cang@quicinc.com, quic_qianyu@quicinc.com Subject: Re: [PATCH RFC v2 1/8] bus: mhi: host: add mhi_power_down_no_destroy() Message-ID: <20240122130947.GD3176@thinkpad> References: <20231127162022.518834-1-kvalo@kernel.org> <20231127162022.518834-2-kvalo@kernel.org> <20231130054250.GC3043@thinkpad> <87v89cq1ci.fsf@kernel.org> <20231220163209.GJ3544@thinkpad> <20231220165113.GK3544@thinkpad> <7a31696b-cf2b-48c0-bad3-327e9ce47172@quicinc.com> <20240104060904.GB3031@thinkpad> <20240122062411.GA3176@thinkpad> <9ac258d7-8a57-4071-af8d-5b07d776135b@quicinc.com> Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <9ac258d7-8a57-4071-af8d-5b07d776135b@quicinc.com> On Mon, Jan 22, 2024 at 04:09:53PM +0800, Baochen Qiang wrote: > > > On 1/22/2024 2:24 PM, Manivannan Sadhasivam wrote: > > On Thu, Jan 04, 2024 at 11:39:12AM +0530, Manivannan Sadhasivam wrote: > > > > + Can, Qiang > > > > [...] > > > > > > > To me it all sounds like the probe deferral is not handled properly in mac80211 > > > > > stack. As you mentioned in the commit message that the dpm_prepare() blocks > > > > > probing of devices. It gets unblocked and trigerred in dpm_complete(): > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/power/main.c#n1131 > > > > > > > > > > So if mac80211/ath11k cannot probe the devices at the dpm_complete() stage, then > > > > > it is definitely an issue that needs to be fixed properly. > > > > To clarify, ath11k CAN probe the devices at dpm_complete() stage. The > > > > problem is kernel does not wait for all probes to finish, and in that way we > > > > will face the issue that user space applications are likely to fail because > > > > they get thawed BEFORE WLAN is ready. > > > > > > > > > > Hmm. Please give me some time to reproduce this issue locally. I will get back > > > to this thread with my analysis. > > > > > > > We reproduced the issue with the help of PCIe team (thanks Can). What we found > > out was, during the resume from hibernation the faliure happens in > > ath11k_core_resume(). Precisely here: > > https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/tree/drivers/net/wireless/ath/ath11k/core.c?h=ath11k-hibernation-support#n850 > > > > This code waits for the QMI messages to arrive and eventually timesout. But the > > impression I got from the start was that the mhi_power_up() always fails during > > resume. In our investigation, we confirmed that the failure is not happening at > > the MHI level.No, mhi_power_up() never fails as it only downloads PBL, > > SBL and waits > for mission mode, no MHI device created hence not affected by the deferred > probe. However in addition to PBL/SBL, ath11k also needs to download m3.bin, > borad.bin and regdb.bin. Those files are part of WLAN firmware and are > downloaded via QMI messages. After mhi_power_up() succeeds > ath11k_core_resume() waits for QMI downloading those files. As you know QMI > relies on MHI channels, these channels are managed by qcom_mhi_qrtr_driver. > Since device probing is deferred, qcom_mhi_qrtr_driver has no chance to run > at this stage. As a result ath11k_core_resume() times out. > Thanks for the info, this clarifies the issue in detail. > > > > I'm not pointing fingers here, but trying to understand why can't you fix > > ath11k_core_resume() to not timeout? IMO this timeout should be handled as a > > deferral case. > Let's see what happens if we do it in a deferral way: > 1. In ath11k_core_resume() we returns success directly without waiting for > QMI downloading other firmware files. > 2. Kernel unblocks device probe and schedules a work item to trigger all > deferred probing. As a result MHI devices are probed by qcom_mhi_qrtr_driver > and finally QMI is online. > 3. kernel continues to resume and wake up userspace applications. > 4. ath11k gets the message, either by kernel PM notification or something > else, that QMI is ready and then downloads other firmware files. > > What happens if userspace applications or network stack immediately initiate > some WLAN request after resume back? Can ath11k handle such request? The > answer is, most likely, no. Because there is no guarantee that QMI finishes > downloading before those request. > What will happen to userspace if ath11k returns an error like -EBUSY or something? Will the netdev completely go away? - Mani > > > > - Mani > > -- மணிவண்ணன் சதாசிவம்