Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756210AbZCFWt0 (ORCPT ); Fri, 6 Mar 2009 17:49:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753853AbZCFWtQ (ORCPT ); Fri, 6 Mar 2009 17:49:16 -0500 Received: from yw-out-2324.google.com ([74.125.46.29]:40937 "EHLO yw-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753104AbZCFWtP convert rfc822-to-8bit (ORCPT ); Fri, 6 Mar 2009 17:49:15 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=BoE/BvtZYh6wUdWcaekz7RKUtrhxAzXNul0vHIxzPjIqMfKadN5CSnJwojgKJFBc76 hxuNbjJ+jIygHp9jGfAXPVXvB1QHvKkCQwO0V8JdOXs7np+A4ck8yYpYgDJrtVQnZoWv wh2PNbz2jzJelsfQFoeHC9aqYoNTE5wfTEaqs= MIME-Version: 1.0 In-Reply-To: <20090306143806.3b126ab4.akpm@linux-foundation.org> References: <1236321780-28718-1-git-send-email-cooloney@kernel.org> <1236321780-28718-5-git-send-email-cooloney@kernel.org> <20090306143806.3b126ab4.akpm@linux-foundation.org> Date: Fri, 6 Mar 2009 17:49:13 -0500 Message-ID: <8bd0f97a0903061449w66c672a7r5197a175b16c61a4@mail.gmail.com> Subject: Re: [PATCH 04/18] Blackfin Serial Driver: Change hardware flowcontrol from poll to interrupt driven. From: Mike Frysinger To: Andrew Morton Cc: Bryan Wu , alan@lxorguk.ukuu.org.uk, linux-kernel@vger.kernel.org, sonic.zhang@analog.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1189 Lines: 30 On Fri, Mar 6, 2009 at 17:38, Andrew Morton wrote: > On Fri, ?6 Mar 2009 14:42:46 +0800 Bryan Wu wrote: >> From: Sonic Zhang >> >> Only CTS bit is affected. >> >> Signed-off-by: Sonic Zhang >> Signed-off-by: Bryan Wu > > Another completely useless changelog. the summary, while brief, describes the change: the flowcontrol is currently implemented by polling, but this changes it to an interrupt based system > Your [PATCH 00/18] email described all these patches as > needed-in-2.6.29 bugfixes. ?As far as I can tell (based on almost zero > information), this patch is not a bugfix. because the current implementation is polling (busy waiting), the kernel will basically hang when the remote asserts hardware flowcontrol pins. if this is only asserted for short periods (less than 1 char time), then it's not really noticed ... but it still destroys latencies. -mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/