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X-CSE-ConnectionGUID: lM7sI2tDTAy/3D6scbpjWw== X-CSE-MsgGUID: 7OLsxJ1sS2CI5t7wgxmn4Q== X-IronPort-AV: E=McAfee;i="6600,9927,11085"; a="24574928" X-IronPort-AV: E=Sophos;i="6.08,193,1712646000"; d="scan'208";a="24574928" Received: from orviesa003.jf.intel.com ([10.64.159.143]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 May 2024 10:54:33 -0700 X-CSE-ConnectionGUID: Ix3a3+nnSBC1vshm3rHFRQ== X-CSE-MsgGUID: vJghpWlyTH6wYE8nRgwRZQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,193,1712646000"; d="scan'208";a="39617573" Received: from smile.fi.intel.com ([10.237.72.54]) by orviesa003.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 May 2024 10:54:30 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.97) (envelope-from ) id 1sBeYF-0000000BKuj-0myM; Mon, 27 May 2024 20:54:27 +0300 Date: Mon, 27 May 2024 20:54:26 +0300 From: Andy Shevchenko To: Douglas Anderson Cc: Greg Kroah-Hartman , Jiri Slaby , John Ogness , Tony Lindgren , linux-arm-msm@vger.kernel.org, Johan Hovold , Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Yicong Yang , Guanbing Huang , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Subject: Re: [PATCH 1/2] serial: port: Don't block system suspend even if bytes are left to xmit Message-ID: References: <20240523232216.3148367-1-dianders@chromium.org> <20240523162207.1.I2395e66cf70c6e67d774c56943825c289b9c13e4@changeid> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240523162207.1.I2395e66cf70c6e67d774c56943825c289b9c13e4@changeid> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo On Thu, May 23, 2024 at 04:22:12PM -0700, Douglas Anderson wrote: > Recently, suspend testing on sc7180-trogdor based devices has started > to sometimes fail with messages like this: > > port a88000.serial:0.0: PM: calling pm_runtime_force_suspend+0x0/0xf8 @ 28934, parent: a88000.serial:0 > port a88000.serial:0.0: PM: dpm_run_callback(): pm_runtime_force_suspend+0x0/0xf8 returns -16 > port a88000.serial:0.0: PM: pm_runtime_force_suspend+0x0/0xf8 returned -16 after 33 usecs > port a88000.serial:0.0: PM: failed to suspend: error -16 > > I could reproduce these problem by logging in via an agetty on the > debug serial port (which was _not_ used for kernel console) and > running: > cat /var/log/messages > ...and then (via an SSH session) forcing a few suspend/resume cycles. > > Tracing through the code and doing some printf debugging shows that printf() ...or... printf()-based > the -16 (-EBUSY) comes from the recently added > serial_port_runtime_suspend(). > > The idea of the serial_port_runtime_suspend() function is to prevent > the port from being _runtime_ suspended if it still has bytes left to > transmit. Having bytes left to transmit isn't a reason to block > _system_ suspend, though. The DEFINE_RUNTIME_DEV_PM_OPS() used by the > serial_port code means that the system suspend function will be > pm_runtime_force_suspend(). In pm_runtime_force_suspend() we can see > that before calling the runtime suspend function we'll call > pm_runtime_disable(). This should be a reliable way to detect that > we're called from system suspend and that we shouldn't look for > busyness. ... > + /* > + * We only want to check the busyness of the port if PM Runtime is > + * enabled. Specifically PM Runtime will be disabled by > + * pm_runtime_force_suspend() during system suspend and we don't want > + * to block system suspend even if there is data still left to > + * transmit. We only want to block regulator PM Runtime transitions. regular > + */ > + if (!pm_runtime_enabled(dev)) > + return 0; -- With Best Regards, Andy Shevchenko