From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fp73Q-0003wv-B2 for barebox@lists.infradead.org; Mon, 13 Aug 2018 07:14:18 +0000 Date: Mon, 13 Aug 2018 09:14:04 +0200 From: Sascha Hauer Message-ID: <20180813071404.buwawoejldsgocho@pengutronix.de> References: <20180508211502.5476-1-andrew.smirnov@gmail.com> <20180514071456.qknyha5bsl6gbkk4@pengutronix.de> <20180515060727.j6zcpqcu7vwbd3bn@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: 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: Andrey Smirnov Cc: Barebox List On Sat, Aug 11, 2018 at 12:35:39PM -0700, Andrey Smirnov wrote: > 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. Applied now, thanks Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox