From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-io0-f195.google.com ([209.85.223.195]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1foZj5-0004HL-9v for barebox@lists.infradead.org; Sat, 11 Aug 2018 19:39:05 +0000 Received: by mail-io0-f195.google.com with SMTP id w11-v6so10779099iob.2 for ; Sat, 11 Aug 2018 12:36:52 -0700 (PDT) MIME-Version: 1.0 References: <20180508211502.5476-1-andrew.smirnov@gmail.com> <20180514071456.qknyha5bsl6gbkk4@pengutronix.de> <20180515060727.j6zcpqcu7vwbd3bn@pengutronix.de> In-Reply-To: <20180515060727.j6zcpqcu7vwbd3bn@pengutronix.de> From: Andrey Smirnov Date: Sat, 11 Aug 2018 12:35:39 -0700 Message-ID: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH] serial: lpuart: Avoid division by zero when requested baudrate is To: Sascha Hauer Cc: Barebox List On Mon, May 14, 2018 at 11:07 PM Sascha Hauer wrote: > > On Mon, May 14, 2018 at 05:20:56PM -0700, Andrey Smirnov wrote: > > On Mon, May 14, 2018 at 12:14 AM, Sascha Hauer wrote: > > > On Tue, May 08, 2018 at 02:15:02PM -0700, Andrey Smirnov wrote: > > >> With serdev device support added there's now a corner case where: > > >> > > >> 1. There is a DT node for a serdev device on one of the UARTs > > >> 2. There is no driver that binds against serdev device's compatibility > > >> string > > >> > > >> with 1 and 2 being true it is possible to end up in a situation where > > >> a particualr UART has not been initalized to any baudrate when > > >> clock_notifier_call_chain() gets called. This effectively translates > > >> to > > >> > > >> set_baudrate(uart, 0); > > >> > > >> which for LPUART driver result in a division by zero. > > > > > > This probably leads to a division by zero for most drivers since > > > dividing by the baudrate is a common pattern. Wouldn't it be better to > > > catch this is console_set_baudrate()? > > > > > > > It would, but none of the drivers that register a callback with > > clock_register_client() (serial_imx.c, serial_auart.c, stm-serial.c, > > serial_lpuart.c and serial_cadence.c) use console_set_badrate() and > > instead call ->setbrg() directly. Probably because > > console_set_baudrate() also handles interactive baudrate switch for > > f_active console devices. Serial_imx.c doesn't preform any division, > > so it is safe and I can go through the rest of them to add appropriate > > checks? Another option is probably to try to come up with common > > clock_register_client() infrastructure(since all of the handlers are > > the same) and keep that check there. > > > > Let me know if you want me to do either. > > I see. For the sake of simplicity I think we can go with your original > patch. In the auart and cadence driver the clock notify stuff is unused, > only copy paste leftover from copying the i.MX driver. That leaves the > lpuart driver which really has this problem. > Sascha, I don't think this patch ever made it into master. I am assuming it just slipped through the cracks. Let me know if anything needs changing for it to be applied. Thanks, Andrey Smirnov _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox