From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2981BC7EE24 for ; Mon, 5 Jun 2023 13:18:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233757AbjFENSH (ORCPT ); Mon, 5 Jun 2023 09:18:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232683AbjFENSG (ORCPT ); Mon, 5 Jun 2023 09:18:06 -0400 Received: from muru.com (muru.com [72.249.23.125]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 418E6CD; Mon, 5 Jun 2023 06:18:05 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by muru.com (Postfix) with ESMTPS id 9C03080FE; Mon, 5 Jun 2023 13:18:04 +0000 (UTC) Date: Mon, 5 Jun 2023 16:18:03 +0300 From: Tony Lindgren To: Chen-Yu Tsai Cc: John Ogness , Greg Kroah-Hartman , Jiri Slaby , Andy Shevchenko , Dhruva Gole , Ilpo =?utf-8?B?SsOkcnZpbmVu?= , Johan Hovold , Sebastian Andrzej Siewior , Vignesh Raghavendra , linux-omap@vger.kernel.org, Andy Shevchenko , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, =?utf-8?B?TsOtY29sYXMgRi4gUi4gQS4=?= Prado , AngeloGioacchino Del Regno , linux-mediatek@lists.infradead.org Subject: Re: [PATCH v12 1/1] serial: core: Start managing serial controllers to enable runtime PM Message-ID: <20230605131803.GA14287@atomide.com> References: <20230525113034.46880-1-tony@atomide.com> <20230602083335.GA181647@google.com> <87a5xii33r.fsf@jogness.linutronix.de> <20230603054139.GR14287@atomide.com> <20230603063533.GS14287@atomide.com> <20230605061511.GW14287@atomide.com> <20230605122447.GY14287@atomide.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org * Chen-Yu Tsai [230605 13:01]: > On Mon, Jun 5, 2023 at 8:24 PM Tony Lindgren wrote: > > > > * Chen-Yu Tsai [230605 11:34]: > > > On Mon, Jun 5, 2023 at 2:15 PM Tony Lindgren wrote: > > > > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c > > > > --- a/drivers/tty/serial/8250/8250_mtk.c > > > > +++ b/drivers/tty/serial/8250/8250_mtk.c > > > > @@ -425,11 +439,10 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios, > > > > static int __maybe_unused mtk8250_runtime_suspend(struct device *dev) > > > > { > > > > struct mtk8250_data *data = dev_get_drvdata(dev); > > > > - struct uart_8250_port *up = serial8250_get_port(data->line); > > > > > > > > /* wait until UART in idle status */ > > > > while > > > > - (serial_in(up, MTK_UART_DEBUG0)); > > > > + (mtk8250_read(data, MTK_UART_DEBUG0)); > > > > > > I believe it still gets stuck here sometimes. > > > > Hmm so maybe you need to mtk8250_write(data, 0, MTK_UART_RATE_FIX) in > > probe before pm_runtime_resume_and_get() that enables the baud clock? > > That's something I changed, so maybe it messes up things. > > I think it has something to do with the do_pm() function calling > the callbacks directly, then also calling runtime PM. Yeah I'm not following really what's going on there.. So then I guess the call for mtk8250_write(data, 0, MTK_UART_RATE_FIX) should be after the pm_runtime_resume_and_get() call. > > Looking at the 8250_mtk git log, it's runtime PM functions seem to only > > currently manage the baud clock so register access should be doable > > without runtime PM resume? > > Actually it only manages the bus clock. The baud clock is simply the system > XTAL which is not gateble. OK > > > With your earlier patch, it could get through registering the port, and > > > the console would show > > > > > > 11002000.serial: ttyS0 at MMIO 0x11002000 (irq = 240, base_baud = > > > 1625000) is a ST16650V2 > > > > > > for the console UART. > > > > OK > > > > > Angelo mentioned that we should be using SLEEP_REQ/SLEEP_ACK registers > > > in the MTK UART hardware. > > > > > > I tried reworking it into your patch here, but it causes issues with the > > > UART-based Bluetooth on one of my devices. After the UART runtime suspends > > > and resumes, something is off and causes the transfers during Bluetooth > > > init to become corrupt. > > > > > > I'll try some more stuff, but the existing code seems timing dependent. > > > If I add too many printk statements to the runtime suspend/resume > > > callbacks, things seem to work. One time I even ended up with broken > > > UARTs but otherwise booted up the system. > > > > Well another thing that now changes is that we now runtime suspend the > > port at the end of the probe. What the 8250_mtk probe was doing earlier > > it was leaving the port baud clock enabled, but runtime PM disabled > > until mtk8250_do_pm() I guess. > > I guess that's the biggest difference? Since the *bus* clock gets disabled, > any access will hang. Is it enough to just support runtime PM? Or do I have > to also have UART_CAP_RPM? Maybe try changing pm_runtime_put_sync() at the end of the probe to just pm_runtime_put_noidle()? Then the driver should be back to where it was with clocks enabled but runtime PM suspended. I don't think you need UART_CAP_RPM right now unless 8250_mtk adds support for autosuspend. That stuff will get replaced by the serial_core generic PM patch from Andy. I think in it's current form 8250_mtk just gets enabled when the port is opened, and disabled when the port is closed. And gets disabled for system suspend. Regards, Tony