From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750963AbdAMAfT (ORCPT ); Thu, 12 Jan 2017 19:35:19 -0500 Received: from smtprelay.synopsys.com ([198.182.60.111]:60686 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750781AbdAMAfR (ORCPT ); Thu, 12 Jan 2017 19:35:17 -0500 Subject: Re: [PATCH RFC] usb: dwc2: host: use msleep() for long delay To: Nicholas Mc Guire , John Youn References: <1484234195-28589-1-git-send-email-hofrat@osadl.org> CC: Greg Kroah-Hartman , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" From: John Youn Message-ID: <3c608701-7bcb-7904-d71e-bacab8ff6eb4@synopsys.com> Date: Thu, 12 Jan 2017 16:35:06 -0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 MIME-Version: 1.0 In-Reply-To: <1484234195-28589-1-git-send-email-hofrat@osadl.org> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.9.138.255] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/12/2017 7:15 AM, Nicholas Mc Guire wrote: > ulseep_range() uses hrtimers and provides no advantage over msleep() > for larger delays. Fix up the 100ms delays here passing the adjusted "min" > value to msleep(). This helps reduce the load on the hrtimer subsystem. > > Link: https://urldefense.proofpoint.com/v2/url?u=http-3A__lkml.org_lkml_2017_1_11_377&d=DgIBAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=U3o8uKoKhWme5_V9D-eeCkB11BFwt4KvWztBgdE9ZpA&m=dvQDbbH_QF2kZjARIDPimFAK95z8eOnw04feJuHCrJg&s=Prc0m1oUG4u8n8TFK-fdgzitMzE2ep6pM3L6y_DQeRs&e= > Fixes: commit 2938fc63e0c2 ("usb: dwc2: Properly account for the force mode delays") > Signed-off-by: Nicholas Mc Guire > --- > Problem was found by cocinelle script. > > Note that this originally was an msleep(25) then commit 2938fc63e0c2 > ("usb: dwc2: Properly account for the force mode delays") changed this > to usleep_range(100000,110000) with the comment in the function head: > > After clearing the bits, wait up to 100 ms to account for any > potential IDDIG filter delay... > > but without explaining why the API was switched to usleep_range() here > It does not look like there is any reason for using a high resolution > timer here - the stated requirement is clearly satisfied by msleep(100) > as well. But it originally was usleep_range(150000, 160000) in > commit 09c96980dc72 ("usb: dwc2: Add functions to set and clear force mode") > so not sure if I am not overlooking some reason for the highrestimer here ? > > This needs to be clarified by someone that knows the details and history > of this device/driver. > > Patch was compile tested with: x86_64_defconfig + CONFIG_USB_DWC2 > > Patch is aginast 4.10-rc3 (localversion-next is next-20170112) > > drivers/usb/dwc2/core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/usb/dwc2/core.c b/drivers/usb/dwc2/core.c > index 11d8ae9..439a21b 100644 > --- a/drivers/usb/dwc2/core.c > +++ b/drivers/usb/dwc2/core.c > @@ -455,7 +455,7 @@ void dwc2_clear_force_mode(struct dwc2_hsotg *hsotg) > dwc2_writel(gusbcfg, hsotg->regs + GUSBCFG); > > if (dwc2_iddig_filter_enabled(hsotg)) > - usleep_range(100000, 110000); > + msleep(100); > } > > /* > +Felipe Acked-by: John Youn John