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 EC0C1208CA; Tue, 17 Dec 2024 21:00:40 +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=1734469241; cv=none; b=R6Fvy06eOmxMPVN0ABBGOqkN/b3rfpX0HsvgRl5Cy9lNfkgbVqkloOhcv7OGt77SkeeBVjNfp8WGb7g6PG4/sEt13lstpaY9oZV0QcrScWDUC2hfZ60D0uzV3v4odjDvtRrlASqLJaGOLVe1Otreq7JfXTqaXJNQcSULcRccBDc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734469241; c=relaxed/simple; bh=gT7SGZ+RgZjr4sjaS4D5vIpdgF1oyCiZb1851h8AvmI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Kc9D20jExEmWGTbyiCFZss0hhLl38+2Cl6fLei+Wyq0jOPc+hGAJ6nWktAXo0ZJJUQTLLH2SAR7BHTo2GL10jAaET14rUZcGE4s4fBMYRUkmuQdoTxj029Vh5mpJaXRYjhnAG3N8/S5P8aJYEbUcn/gJYuYPyAUl5salPtDPui8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=g50/Vin1; 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="g50/Vin1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 748EAC4CED3; Tue, 17 Dec 2024 21:00:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1734469240; bh=gT7SGZ+RgZjr4sjaS4D5vIpdgF1oyCiZb1851h8AvmI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=g50/Vin1NMs21PVMw5jM8YUVvpZ8d1U3+GXgcQKbRuW36vV52pR70iCtjvcVDKDW+ DLidMVudZGsMaHwZXQcYRVQw5r6fX+rRDOQw9xG+mgt8HYsn+s5UrNNywyNwQG3yPv Vb6IYog2J7Z7S7MsfLGHYn+kc050dFvj2IvP9TVouN31G9DFRT9hWJi65A9Qk7UFDD LviM9kB/cP704mawxAKgkuT7NDhvMJk7qdlX7hXQ1Cd3+nJ/GnY2a8Pij6TYjGAtdW KTt4i3kEtN56Lahc/Qmti+FKoEnmwcPkuR1faGn7nr0xQ7MDG9TLoGGk7S+WEaYYc8 pUy8Z9lA8AVtw== Message-ID: Date: Tue, 17 Dec 2024 23:00:35 +0200 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 4/5] xhci: introduce xhci->lost_power flag To: =?UTF-8?Q?Th=C3=A9o_Lebrun?= , Peter Chen , Pawel Laszczak , Greg Kroah-Hartman , Mathias Nyman Cc: =?UTF-8?Q?Gr=C3=A9gory_Clement?= , Thomas Petazzoni , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org References: <20241210-s2r-cdns-v6-0-28a17f9715a2@bootlin.com> <20241210-s2r-cdns-v6-4-28a17f9715a2@bootlin.com> <70aced7f-0311-43b9-96af-c8325c39ff2b@kernel.org> Content-Language: en-US From: Roger Quadros In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 13/12/2024 18:03, Théo Lebrun wrote: > On Thu Dec 12, 2024 at 1:37 PM CET, Roger Quadros wrote: >> On 10/12/2024 19:13, Théo Lebrun wrote: >>> The XHCI_RESET_ON_RESUME quirk allows wrappers to signal that they >>> expect a reset after resume. It is also used by some to enforce a XHCI >>> reset on resume (see needs-reset-on-resume DT prop). >>> >>> Some wrappers are unsure beforehands if they will reset. Add a mechanism >>> to signal *at resume* if power has been lost. Parent devices can set >>> this flag, that defaults to false. >>> >>> The XHCI_RESET_ON_RESUME quirk still triggers a runtime_pm_get() on the >>> controller. This is required as we do not know if a suspend will >>> trigger a reset, so the best guess is to avoid runtime PM. >>> >>> Signed-off-by: Théo Lebrun >>> --- >>> drivers/usb/host/xhci.c | 3 ++- >>> drivers/usb/host/xhci.h | 6 ++++++ >>> 2 files changed, 8 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c >>> index 5ebde8cae4fc44cdb997b0f61314e309bda56c0d..ae2c8daa206a87da24d58a62b0a0485ebf68cdd6 100644 >>> --- a/drivers/usb/host/xhci.c >>> +++ b/drivers/usb/host/xhci.c >>> @@ -1017,7 +1017,8 @@ int xhci_resume(struct xhci_hcd *xhci, pm_message_t msg) >>> >>> spin_lock_irq(&xhci->lock); >>> >>> - if (hibernated || xhci->quirks & XHCI_RESET_ON_RESUME || xhci->broken_suspend) >>> + if (hibernated || xhci->quirks & XHCI_RESET_ON_RESUME || >>> + xhci->broken_suspend || xhci->lost_power) >>> reinit_xhc = true; >>> >>> if (!reinit_xhc) { >>> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h >>> index 4914f0a10cff42dbc1448dcf7908534d582c848e..32526df75925989d40cbe7d59a187c945f498a30 100644 >>> --- a/drivers/usb/host/xhci.h >>> +++ b/drivers/usb/host/xhci.h >>> @@ -1645,6 +1645,12 @@ struct xhci_hcd { >>> unsigned broken_suspend:1; >>> /* Indicates that omitting hcd is supported if root hub has no ports */ >>> unsigned allow_single_roothub:1; >>> + /* >>> + * Signal from upper stacks that we lost power during system-wide >>> + * suspend. Its default value is based on XHCI_RESET_ON_RESUME, meaning >>> + * it is safe for wrappers to not modify lost_power at resume. >>> + */ >>> + unsigned lost_power:1; >> >> I suppose this is private to XHCI driver and not legitimate to be accessed >> by another driver after HCD is instantiated? > > Yes it is private. > >> Doesn't access to xhci_hcd need to be serialized via xhci->lock? > > Good question. In theory maybe. In practice I don't see how > cdns_host_resume(), called by cdns_resume(), could clash with anything > else. I'll add that to be safe. > >> Just curious, what happens if you don't include patch 4 and 5? >> Is USB functionality still broken for you? > > No it works fine. Patches 4+5 are only there to avoid the below warning. > Logging "xHC error in resume" is a lie, so I want to avoid it. How is it a lie? The XHCI controller did loose its save/restore state during a PM operation. As far as XHCI is concerned this is an error. no? > >> Doesn't XHCI driver detect that power was lost and issue a reset in any case >> via the below code >> >> /* re-initialize the HC on Restore Error, or Host Controller Error */ >> if ((temp & (STS_SRE | STS_HCE)) && >> !(xhci->xhc_state & XHCI_STATE_REMOVING)) { >> reinit_xhc = true; >> if (!xhci->broken_suspend) >> xhci_warn(xhci, "xHC error in resume, USBSTS 0x%x, Reinit\n", temp); >> } >> >>> /* cached extended protocol port capabilities */ >>> struct xhci_port_cap *port_caps; >>> unsigned int num_port_caps; >>> > > I'll wait for your opinion on the [PATCH v6 2/5] email thread before > sending a new revision. Sorry for the delay. I'm not an expert in PM but will give my opinion there anyways. > > Thanks, > > -- > Théo Lebrun, Bootlin > Embedded Linux and Kernel engineering > https://bootlin.com > > -- cheers, -roger