From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753943AbeDKQQW (ORCPT ); Wed, 11 Apr 2018 12:16:22 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:35650 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752798AbeDKQQV (ORCPT ); Wed, 11 Apr 2018 12:16:21 -0400 Message-ID: <1523463379.3221.18.camel@HansenPartnership.com> Subject: Re: [PATCH v2] dec: tulip: de4x5: Replace mdelay with usleep_range in de4x5_hw_init From: James Bottomley To: Jia-Ju Bai , davem@davemloft.net, stephen@networkplumber.org, johannes.berg@intel.com, arvind.yadav.cs@gmail.com, dhowells@redhat.com Cc: netdev@vger.kernel.org, linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 11 Apr 2018 09:16:19 -0700 In-Reply-To: <1523461182-5897-1-git-send-email-baijiaju1990@gmail.com> References: <1523461182-5897-1-git-send-email-baijiaju1990@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2018-04-11 at 23:39 +0800, Jia-Ju Bai wrote: > de4x5_hw_init() is never called in atomic context. > > de4x5_hw_init() is only called by de4x5_pci_probe(), which is only  > set as ".probe" in struct pci_driver. > > Despite never getting called from atomic context, de4x5_hw_init()  > calls mdelay() to busily wait. This is not necessary and can be > replaced with usleep_range() to  avoid busy waiting. > > This is found by a static analysis tool named DCNS written by myself. > And I also manually check it. Did you actually test this? The usual reason for wanting m/udelay is that the timing must be exact. The driver is filled with mdelay()s for this reason. The one you've picked on is in the init path so it won't affect the runtime in any way. I also don't think we have the hrtimer machinery for usleep_range() to work properly on parisc, so I don't think the replacement works. James