From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.128.49 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793626481; b=cr4CMwXb3ZMOENWYAZ9I0ruuOWf/UDJHQRJe8F9zKYky/W+h0Wu2RZ7plymR5/9QxxNa fcER34UTysoVd+7z3mdTqR65b68N8sZDxQfucTKW7omxL0oMV5SbHbC2g8VcKmiYf/TWC 3CeofQUdTS5OgUS7qmQXwWO/7tqdGpTtWNdcEjU2GDixwfScP/vIEwjO5A027GaIe/UYr hXEVeOp9CAkPWpoOW7ChL3DEjHqqjjC1jtVLj8M45y5fLsBTBDuKW1XI2CtHrmZCUTzA9 wxeXNTkvEYoGDEj8EEOpRlHrssdWNgUPc6u2ntiVvzSrRIfsRFgACdwtKq0YoS87dhA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793626481; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=6R/u431umGtSkGq0ekXuHtMmDyjJRoaSYLM3qGkDCO4=; b=c1sjlajIi7/Swxj7Si0X+lYzz0VKDv0ifAQSxn4JVUMH5h/VK6I12qnIRjxA9XEeeNnq zcJa5SRv4EpU5CPUA6yrn4Mjv/lynYtKM5oxI8eu4nipGLMsMKYNduZiDJJ1LNQsUqngL bNFCVr+8+OvN586iFNd4+skP2gwlzwr0MbffbQgHoE0QTMctKsHwDDUa/8jGQey8w5yvc qDtnYtNv1nUU4Z5ib7/dyVRP9jFqKrstNeomL27QLh2bO1X+nuP6A/XKGKEFenrgt7suM etXAR4GWjWzpKbor+xdLpP9WjAo/YulXCELVC9prBcw3vOcT+o7wl4y0T9ACyYc9LYA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=vxkCrL7D; arc=none smtp.remote-ip=209.85.128.49 Received: from mail-wm1-f49.google.com (mail-wm1-f49.google.com [209.85.128.49]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB8C9606A32C for ; Mon, 2 Nov 2026 13:34:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org AB8C9606A32C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=vxkCrL7D Received: by mail-wm1-f49.google.com with SMTP id 5b1f17b1804b1-4a1fbd52ab6so22764485e9.0 for ; Mon, 02 Nov 2026 05:34:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20260707; t=1793626479; x=1794231279; darn=vger.kernel.org; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=6R/u431umGtSkGq0ekXuHtMmDyjJRoaSYLM3qGkDCO4=; b=vxkCrL7DvCsMFVKdBCQhqjoeH7mIRO46s2nHFM91xUvxoS67ayd64OS225aEifEjTG bh8Mvh5N+eeUsjMlf9qorQkDt3mSdacKQfcwrRZf46m40gx7iz0kWYv4I/SEFV4T/kyN yavJkGnQ9hwYQXohz7ijamiFdGtmWSA8D+w3pVd3l01M6+3pZEI6PH8KrrWgCCJvc4Ip YtvrJ42dOYoBenv1dgf2fEdS+Zqw0BCDOfPa31q6ouwp2yHu25lYCgkesXPJLew6R+TN WR0N2QrvfP817RY6/3cDexrO5+7KRVpBemi8NMsJ1TAZFVM6cXybZ/YkIscEk6kKU454 4cfw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793626479; x=1794231279; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=6R/u431umGtSkGq0ekXuHtMmDyjJRoaSYLM3qGkDCO4=; b=h9dHix63E0WGDmqZ0ZyYA76Ok1thW3JzC7Xk2tiVdU4W2bG/EfQ43fGdheivdmy0wc YaVv/XQVxyklsAacLaL0D25oiYuhXLmTl+O+8EQRsIXwO2ME9DkfFmXZDGgPfYOh5FgO +5AcK1/F0baBbSqZHo1eCyYEprUtWhStwxg4r3ohpeBI2eyyLg+O4nyK6ZitTMQxXofC KIeb+t5t77GzBBdy6OS+1WVGs36ciCgKtyEjVtyDVa0OIEtmaKexjdHaYZuBHKKLvtSY PLVfEDKGMCLy+r+IQwFJKISv79AsxTGUSF1W+I9J3E9peHh9hiri4uA5i6bzx+Dvi2I+ e8PQ== X-Forwarded-Encrypted: i=1; AKwUvBz+SlZ/72ng9Eisbkd40T4Ln6awS9RZRPhjv1MvM7I6nQ+VR+BKrVJHLBEIuBljq6A4aGoB5u05DrfaYd4=@vger.kernel.org X-Gm-Message-State: AFq9FYK2eONsAYOU4xAqYvsobJdEUa4FR6LsXOJJEqs+7DZGUOjPWzWq +lat338M/pcKlN4AQhiY8ntH7CR7/sE64Y6oXX4mEUcrxgVFsg3DSaDT X-Gm-Gg: AYBFou1+ON8cEkvgDjNZMMZMSWBe0yRhhbBh7al0DfXv5cx+tiKFUmwz6IokIlLPNBw isMZESkWfanQaTCeCC7rhuYM0JBk/00yKlf3jhtMNbgdFYpKiiwLfpm+hKEK3eh0Kt1SL/xIrS9 ZRC+QbJrh1olA2k51l3HcHLzYHIPfyidkF001E+K+k5/WBjK58kMjwRuULUBUcAW2v9XoAfbSAK wDzcjsuudAMBoSFBSv3yvAFb4R6G84CY+MsC/CX69QuTegr6FLmf9lKXmToKgjhlhgdcPWKAvVH btEygHucC7pdylyOyz0AUHDTGYF8SA9v2n57FV7JDa3/DcY6hhLOVbdr/sozB0n8ZfkCPaNpB3q OEWIbg++0jr/ltl6NZbAXWlWOJvUokioVkXTTJg/aHouDhWE+DtmP+LStnV1zN+es83lqe+tvlM Vz7ls7M2k57V4bllHQOVrzFSmH866oSViceX9QwYXQoa3n1k/Sz+xTH6xo7dNB6K6yMfU7gGxkH 5XcxlAeplv35EHuMmT1gXbZLShH6XHaan5X14QySBY04FUStZdy926FjmAgwYPH7szJBczFrTBW AfXvRgwSUn4mEPmtMNTFuXpGxzZqlMtQNIt1jneXd+uDsQplT/vKlqjluw== X-Received: by 2002:a05:600c:4f55:b0:4a3:d327:6ed with SMTP id 5b1f17b1804b1-4ac182dcba3mr253672315e9.17.1793626479081; Mon, 02 Nov 2026 05:34:39 -0800 (PST) Received: from foxbook (bgu81.neoplus.adsl.tpnet.pl. [83.28.84.81]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4abf396dfdbsm274233715e9.1.2026.11.02.05.34.37 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Mon, 02 Nov 2026 05:34:38 -0800 (PST) Date: Mon, 2 Nov 2026 14:34:35 +0100 From: Michal Pecio To: Alan Stern Cc: Jianping Liu , gregkh@linuxfoundation.org, dakr@kernel.org, shashank.mahadasyam@sony.com, johan@kernel.org, hadess@hadess.net, frankjpliu@tencent.com, guanyulin@google.com, gary@garyguo.net, rafael.j.wysocki@intel.com, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, Mathias Nyman Subject: Re: [PATCH] usb: core: raise root-hub autosuspend delay to stop a busy-loop Message-ID: <20261102143435.044064df.michal.pecio@gmail.com> In-Reply-To: References: <20261028041859.1061836-1-frankljpliu@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 29 Oct 2026 22:23:02 -0400, Alan Stern wrote: > On Wed, Oct 28, 2026 at 12:18:59PM +0800, Jianping Liu wrote: > > From: Jianping Liu > > > > hub_probe() sets the hub autosuspend delay to 0. An idle hub is > > therefore suspended at once, with no waiting time. > > > > Suspending the root hub can fail. While a port reports over-current > > or a connect change, xHCI refuses the bus suspend and returns > > -EBUSY. usb_runtime_suspend() returns that error. The hub is > > resumed, and when its status URB completes the same suspend runs > > again. Yes, I have seen this ping-ponging before. > > Why should root hubs be special? An ordinary hub doesn't refuse to > suspend because of an over-current or connect change. xhci-hcd ought > to behave the same way. IDK what happened there, but we have this: commit e9fb08d617bfae5471d902112667d0eeb9dee3c4 Author: Mathias Nyman Date: Tue Apr 21 17:08:21 2020 +0300 xhci: prevent bus suspend if a roothub port detected a over-current condition Suspending the bus and host controller while a port is in a over-current condition may halt the host. Also keep the roothub running if over-current is active. Cc: Signed-off-by: Mathias Nyman Link: https://lore.kernel.org/r/20200421140822.28233-3-mathias.nyman@linux.intel.com Signed-off-by: Greg Kroah-Hartman Regards, Michal