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 5B40DC25B06 for ; Mon, 15 Aug 2022 12:44:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242376AbiHOMo6 (ORCPT ); Mon, 15 Aug 2022 08:44:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242375AbiHOMo5 (ORCPT ); Mon, 15 Aug 2022 08:44:57 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8AB9DDEF4; Mon, 15 Aug 2022 05:44:56 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 30F3C611D3; Mon, 15 Aug 2022 12:44:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05178C433D6; Mon, 15 Aug 2022 12:44:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660567495; bh=TZYLlk3W3nAvHUdt4q3X9iVBQXyr803loTxzGJkJI2k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HgK/cRAMArBD901BXT4oKqd9Hfy8rwRlXYQW+58fPB8I2OV/5kKZ2Rg8gjUEzzrcT iPTY01Tm8MWz3vByClibaw61UQ16KhdrzscecQkv/YSjZ6W9tUjdQGTWPBDXxLwYRQ CYKP8Ll3RB0hQajcmnr/LGPTqiA4WUwmp+BeG4OQ= Date: Mon, 15 Aug 2022 14:44:52 +0200 From: Greg Kroah-Hartman To: Ilpo =?iso-8859-1?Q?J=E4rvinen?= Cc: Sasha Levin , stable-commits@vger.kernel.org, Jiri Slaby , stable@vger.kernel.org Subject: Re: Patch "serial: Store character timing information to uart_port" has been added to the 5.18-stable tree Message-ID: References: <20220813215542.1973126-1-sashal@kernel.org> <1119a468-deef-8edb-ac92-ae02c18ca22@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1119a468-deef-8edb-ac92-ae02c18ca22@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Mon, Aug 15, 2022 at 01:54:32PM +0300, Ilpo Järvinen wrote: > On Sat, 13 Aug 2022, Sasha Levin wrote: > > > This is a note to let you know that I've just added the patch titled > > > > serial: Store character timing information to uart_port > > > > to the 5.18-stable tree which can be found at: > > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary > > > > The filename of the patch is: > > serial-store-character-timing-information-to-uart_po.patch > > and it can be found in the queue-5.18 subdirectory. > > > > If you, or anyone else, feels it should not be added to the stable tree, > > please let know about it. > > > > commit 5517053a2e0b30a1e35f90504446af4a2c4920e8 > > Author: Ilpo Järvinen > > Date: Mon Apr 25 17:33:58 2022 +0300 > > > > serial: Store character timing information to uart_port > > > > [ Upstream commit 31f6bd7fad3b149a1eb6f67fc2e742e4df369b3d ] > > > > Struct uart_port currently stores FIFO timeout. Having character timing > > information readily available is useful. Even serial core itself > > determines char_time from port->timeout using inverse calculation. > > > > Store frame_time directly into uart_port. Character time is stored in > > nanoseconds to have reasonable precision with high rates. To avoid > > overflow, 64-bit math is necessary. > > > > It might be possible to determine timeout from frame_time by > > multiplying it with fifosize as needed but only part of the users seem > > to be protected by a lock. Thus, this patch does not pursue storing > > only frame_time in uart_port. > > > > Signed-off-by: Ilpo Järvinen > > Link: https://lore.kernel.org/r/20220425143410.12703-2-ilpo.jarvinen@linux.intel.com > > Signed-off-by: Greg Kroah-Hartman > > Signed-off-by: Sasha Levin > > > > diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c > > index 95d8d1fcd543..6b07b7b41354 100644 > > --- a/drivers/tty/serial/serial_core.c > > +++ b/drivers/tty/serial/serial_core.c > > @@ -24,6 +24,7 @@ > > #include > > #include > > #include > > +#include > > #include > > > > #include > > @@ -333,15 +334,18 @@ void > > uart_update_timeout(struct uart_port *port, unsigned int cflag, > > unsigned int baud) > > { > > - unsigned int size; > > + unsigned int size = tty_get_frame_size(cflag); > > + u64 frame_time; > > > > - size = tty_get_frame_size(cflag) * port->fifosize; > > + frame_time = (u64)size * NSEC_PER_SEC; > > + size *= port->fifosize; > > > > /* > > * Figure the timeout to send the above number of bits. > > * Add .02 seconds of slop > > */ > > port->timeout = (HZ * size) / baud + HZ/50; > > + port->frame_time = DIV64_U64_ROUND_UP(frame_time, baud); > > } > > EXPORT_SYMBOL(uart_update_timeout); > > > > @@ -1610,10 +1614,8 @@ static void uart_wait_until_sent(struct tty_struct *tty, int timeout) > > * Note: we have to use pretty tight timings here to satisfy > > * the NIST-PCTS. > > */ > > - char_time = (port->timeout - HZ/50) / port->fifosize; > > - char_time = char_time / 5; > > - if (char_time == 0) > > - char_time = 1; > > + char_time = max(nsecs_to_jiffies(port->frame_time / 5), 1UL); > > + > > if (timeout && timeout < char_time) > > char_time = timeout; > > > > diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h > > index ca57d686d4d1..409573ea5ea4 100644 > > --- a/include/linux/serial_core.h > > +++ b/include/linux/serial_core.h > > @@ -232,6 +232,7 @@ struct uart_port { > > int hw_stopped; /* sw-assisted CTS flow state */ > > unsigned int mctrl; /* current modem ctrl settings */ > > unsigned int timeout; /* character-based timeout */ > > + unsigned int frame_time; /* frame timing in ns */ > > unsigned int type; /* port type */ > > const struct uart_ops *ops; > > unsigned int custom_divisor; > > > > Why is this change necessary for stable? The change was made simply to > make some other feature changes following a lot simpler but I don't think > there is any known bug/issue it would be fixing. Good point, now dropped from 5.15.y and 5.18.y, thanks. greg k-h