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 4.80.1 #2 (Red Hat Linux)) id 1aGMEs-0005T1-64 for barebox@lists.infradead.org; Tue, 05 Jan 2016 07:41:07 +0000 Date: Tue, 5 Jan 2016 08:40:43 +0100 From: Sascha Hauer Message-ID: <20160105074043.GL13058@pengutronix.de> References: <1451627918-31967-1-git-send-email-andrew.smirnov@gmail.com> <1451627918-31967-3-git-send-email-andrew.smirnov@gmail.com> <20160104092743.GF13058@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 3/6] ARM: Fix exception table setup in MMU-less mode To: Andrey Smirnov Cc: "barebox@lists.infradead.org" On Mon, Jan 04, 2016 at 09:01:23AM -0800, Andrey Smirnov wrote: > >> + > >> +#define __exceptions_size (__exceptions_stop - __exceptions_start) > >> + > >> +#if __LINUX_ARM_ARCH__ >= 7 > >> + > > > > This does not work. In arch/arm/Makefile we have: > > > > arch-$(CONFIG_CPU_32v7) :=-D__LINUX_ARM_ARCH__=7 $(call cc-option,-march=armv7-a,-march=armv5t -Wa$(comma)-march=armv7-a) > > arch-$(CONFIG_CPU_32v6) :=-D__LINUX_ARM_ARCH__=6 $(call cc-option,-march=armv6,-march=armv5t -Wa$(comma)-march=armv6) > > arch-$(CONFIG_CPU_32v5) :=-D__LINUX_ARM_ARCH__=5 $(call cc-option,-march=armv5te,-march=armv4t) > > arch-$(CONFIG_CPU_32v4T) :=-D__LINUX_ARM_ARCH__=4 -march=armv4t > > > > We can build barebox with support for multiple ARM architectures, in this > > case __LINUX_ARM_ARCH__ is set to the smallest supported ARM architecture. > > > > You can encapsulate this code in a #ifdef CONFIG_CPU_32v7 to make sure > > it's only compiled when ARMv7 support is enabled. Then we still can not > > be sure that we actually run on ARMv7, we'll need an additional runtime > > check for: > > > > if (cpu_architecture() >= CPU_ARCH_ARMv7) > > > > Ah, good point. Will fix. > > >> +static struct resource *place_vector_table(void) > >> +{ > >> + int i; > >> + struct resource *vectors = NULL; > >> + resource_size_t addr[2] = { 0x00000000, 0xFFFF0000 }; > >> + > >> + for (i = 0; i < ARRAY_SIZE(addr); i++) { > >> + vectors = request_sdram_region("exceptions", > >> + addr[i], > >> + __exceptions_size); > >> + if (vectors) > >> + break; > >> + } > >> + > >> + return vectors; > >> +} > >> + > >> +static int nommu_v4_vectors_init(void) > >> +{ > >> + u32 cr; > >> + struct resource *vectors; > >> + > >> + vectors = place_vector_table(); > >> + if (!vectors) { > >> + pr_crit("Critical Error: Can't place exception vector table\n"); > >> + return 0; > >> + } > > > > Several SoCs do not have SDRAM at 0x0 and 0xFFFF0000, so on these SoCs > > we would always see this message and have no chance to fix it. > > I am not sure I see why this is a problem. Those SoC physically can't > support this feature, so if you disable MMU you basically choose for > boot ROM to handle the exceptions. "Critical Error: Can't place exception vector table" implies that something went really wrong. We shouldn't print such a message when everything is fine. If we want to merge this code we should lower the message to pr_debug. > > > > > Given that the < ARMv7 path is untested anyway I suggest to just skip it > > and require MMU support to get exception support (unless someone has a > > hardware to test this on). > > The code seemed rather trivial, so I was hoping to save people some > legwork, but sure I'll drop that portion in the next version. >From a quick grep through the code it seems that Nomadik is the only architecture that could currently make use of the code. 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