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 703C4C25B0E for ; Mon, 15 Aug 2022 10:54:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229589AbiHOKyi (ORCPT ); Mon, 15 Aug 2022 06:54:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39702 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229456AbiHOKyh (ORCPT ); Mon, 15 Aug 2022 06:54:37 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C7A311471; Mon, 15 Aug 2022 03:54:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1660560876; x=1692096876; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=BbMX5OoD9X/4qwD0ZfWbQNkjrsvKgf2TT09P+dyjnCE=; b=GofSvdEKPnQqXImenfQbx/IxVDO5Kuhq3hfp6zSi4viIBc0bYKd3gvI2 0Zc1ViZlh6ymuPJ9jbvwnLYodUM+GhKS2z4CzWT+590TxK/2oo7csEuHc Z8Mns3Ripns7SaCEaml9kOs4gjVXeWDUiPpxsP5B/jiqccnq04vf5HuHx wHHkXUtvEDNz73TlXMtDb/8Gvi9OAF/RadExO43MQoCA6Bl7FUP1KC25R DeNqLc/2HyzRDGM/XLW1RcASicg0zve9iCsJSU7wQNiot4XyVCekJMyOL eDy+YtVKSiG6+ly8GfQWGXHSO2VwWCkARbnos1rACRm+FdBwuXY0yledZ A==; X-IronPort-AV: E=McAfee;i="6400,9594,10439"; a="272328147" X-IronPort-AV: E=Sophos;i="5.93,238,1654585200"; d="scan'208";a="272328147" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Aug 2022 03:54:36 -0700 X-IronPort-AV: E=Sophos;i="5.93,238,1654585200"; d="scan'208";a="666621609" Received: from atarakan-mobl1.ger.corp.intel.com ([10.252.50.133]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Aug 2022 03:54:34 -0700 Date: Mon, 15 Aug 2022 13:54:32 +0300 (EEST) From: =?ISO-8859-15?Q?Ilpo_J=E4rvinen?= To: Sasha Levin cc: stable-commits@vger.kernel.org, Greg Kroah-Hartman , 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 In-Reply-To: <20220813215542.1973126-1-sashal@kernel.org> Message-ID: <1119a468-deef-8edb-ac92-ae02c18ca22@linux.intel.com> References: <20220813215542.1973126-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="8323329-1735551488-1660560879=:1723" Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-1735551488-1660560879=:1723 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT 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. -- i. --8323329-1735551488-1660560879=:1723--