Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752226AbaAFBSz (ORCPT ); Sun, 5 Jan 2014 20:18:55 -0500 Received: from mga14.intel.com ([143.182.124.37]:58942 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752072AbaAFBSy (ORCPT ); Sun, 5 Jan 2014 20:18:54 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,609,1384329600"; d="scan'208";a="332214372" Message-ID: <1388971251.2960.11.camel@ymzhang> Subject: Re: [PATCH] pnp: Bypass the calling to pnp_stop_dev at suspend when there is a protocol suspend From: Yanmin Zhang Reply-To: yanmin_zhang@linux.intel.com To: shuox.liu@intel.com, rafael.j.wysocki@intel.com Cc: linux-kernel@vger.kernel.org, bhelgaas@google.com, yanmin.zhang@intel.com Date: Mon, 06 Jan 2014 09:20:51 +0800 In-Reply-To: <1387848951-26999-1-git-send-email-shuox.liu@intel.com> References: <1387848951-26999-1-git-send-email-shuox.liu@intel.com> Organization: Intel. Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.6.4-0ubuntu1 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 二, 2013-12-24 at 09:35 +0800, shuox.liu@intel.com wrote: > From: Zhang Yanmin > > pnp pnp_bus_suspend/_resume have an issue. > pnp_bus_suspend calls pnp_stop_dev to disable the device. With ACPI, > pnp_stop_dev turns off the dev usually. Then, > pnp_bus_suspend=>pnp_dev->protocol->suspend accesses the device and > suspend it again. > > pnp_bus_resume has the similar issue. > > Another issue is firmware might just provide _DIS, but no_STS method. > > The patch fixes it by adding a checking. If there is > pnp_dev->protocol->suspend, pnp_bus_suspend doesn't call pnp_stop_dev. > Do the similar thing for _resume. Rafael, What's your idea about this patch? We hit the issue when enabling Android on a latest tablet. After suspend-to-ram wakeup, serial console doesn't work. This serial port is bound by pnpcore driver. At suspending, static int __pnp_bus_suspend(struct device *dev, pm_message_t state) { ... if (pnp_can_disable(pnp_dev)) { error = pnp_stop_dev(pnp_dev); if (error) return error; } if (pnp_dev->protocol->suspend) pnp_dev->protocol->suspend(pnp_dev, state); return 0; } pnp_stop_dev calls dev->protocol->disable. As for ACPI device, that disable callback calls _DIS. Based on ACPI spec, driver need turn off the device before disabling it by _DIS. That means, after pnp_stop_dev returns, the device is at OFF state. Then, __pnp_bus_suspend calls pnp_dev->protocol->suspend, which continues to access the device while the device is at OFF. Our firmware just provides _DIS for the device. There is no _STS method. Then, after wakeup, the device doesn't work. But just like what the patch points out, pnp_dev->protocol->suspend continues to access the device while the device is at OFF. It's not safe. The patch looks like a workaround. Another possible fix is to just delete the calling of pnp_stop_dev in function __pnp_bus_suspend, as suspend is not equal to _disable_. The deletion might be a little intrusive. That's why we sent a workaround patch to LKML. Which one is better? Thanks, Yanmin > > Signed-off-by: Zhang Yanmin > Signed-off-by: Liu ShuoX > --- > drivers/pnp/driver.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/drivers/pnp/driver.c b/drivers/pnp/driver.c > index f748cc8..2512e47 100644 > --- a/drivers/pnp/driver.c > +++ b/drivers/pnp/driver.c > @@ -176,7 +176,7 @@ static int __pnp_bus_suspend(struct device *dev, pm_message_t state) > return error; > } > > - if (pnp_can_disable(pnp_dev)) { > + if (pnp_can_disable(pnp_dev) && !pnp_dev->protocol->suspend) { > error = pnp_stop_dev(pnp_dev); > if (error) > return error; > @@ -215,9 +215,7 @@ static int pnp_bus_resume(struct device *dev) > error = pnp_dev->protocol->resume(pnp_dev); > if (error) > return error; > - } > - > - if (pnp_can_write(pnp_dev)) { > + } else if (pnp_can_write(pnp_dev)) { > error = pnp_start_dev(pnp_dev); > if (error) > return error; -- 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/