From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.chez-thomas.org (hermes.mlbassoc.com [64.234.241.98]) by mx1.pokylinux.org (Postfix) with ESMTP id 4EEC74C80188 for ; Thu, 9 Jun 2011 06:20:43 -0500 (CDT) Received: by mail.chez-thomas.org (Postfix, from userid 999) id C7DE01660303; Thu, 9 Jun 2011 05:20:42 -0600 (MDT) X-Spam-Checker-Version: SpamAssassin 3.3.2-r929478 (2010-03-31) on hermes.chez-thomas.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=4.0 tests=ALL_TRUSTED,BAYES_00 autolearn=unavailable version=3.3.2-r929478 Received: from [127.0.0.1] (localhost.localdomain [127.0.0.1]) by mail.chez-thomas.org (Postfix) with ESMTP id D632B16602B9; Thu, 9 Jun 2011 05:20:39 -0600 (MDT) Message-ID: <4DF0AC87.2060901@mlbassoc.com> Date: Thu, 09 Jun 2011 05:20:39 -0600 From: Gary Thomas User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10 MIME-Version: 1.0 To: Khem Raj References: <4DEFB4BA.7050902@mlbassoc.com> <4DEFBD77.7000400@linux.intel.com> <4DF016F0.4080106@gmail.com> <4DF02EDF.5040502@mlbassoc.com> <4DF06CB0.1040501@gmail.com> In-Reply-To: <4DF06CB0.1040501@gmail.com> Cc: Poky Project Subject: Re: BeagleBoard using GCC 4.6.0 X-BeenThere: poky@yoctoproject.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Poky build system developer discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 09 Jun 2011 11:20:43 -0000 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit On 06/09/2011 12:48 AM, Khem Raj wrote: > On 06/08/2011 07:24 PM, Gary Thomas wrote: >> On 06/08/2011 06:42 PM, Khem Raj wrote: >>> On 06/08/2011 11:20 AM, Saul Wold wrote: >>>> On 06/08/2011 10:43 AM, Gary Thomas wrote: >>>>> Now that Poky is using GCC 4.6.0, has anyone actually checked the >>>>> operation on the BeagleBoard? I suspect that you'll find that the >>>>> EHCI USB does not work. I can't really check here as I don't trust >>>>> the EHCI on my BeagleBoard rev C3 (not xM). >>>>> >>>>> That said, I've tried this new compiler (previously reported) on >>>>> my own OMAP/3530 board which uses the same 2.6.37 kernel (just not >>>>> the linux-yocto version). When I build my kernel with GCC 4.5.2, >>>>> it works perfectly, but fails with GCC 4.6.0 (I trust the hardware). >>>>> >>>>> I've isolated it down to at least the function 'ehci_hub_control' >>>>> (but I suspect the problem is more fundamental). Comparing the code >>>>> generated by the two compilers with the same source tree, this function >>>>> is dramatically different. I can see why it's failing, I just don't >>>>> know why the compiler is doing what it's doing. >>>>> >>>> >>>> Gary, >>>> >>>> I am not sure if Khem Raj is on this list, so I am forwarding it to him, >>>> he might have some insight. >>>> >>>> Sau! >>>> >>>> >>>>> The lines at drivers/usb/host/ehci-hub.c:841 >>>>> case GetPortStatus: >>>>> if (!wIndex || wIndex > ports) >>>>> goto error; >>>>> wIndex--; >>>>> status = 0; >>>>> temp = ehci_readl(ehci, status_reg); >>>>> >>>>> are being compiled very differently. >>>>> >>>>> With GCC 4.5.2: >>>>> 0xc0229810 : cmp r3, #0 ; 0x0 >>>>> 0xc0229814 : beq 0xc0229df8 >>>>> >>>>> 0xc0229818 : cmp r3, r0 >>>>> 0xc022981c : bgt 0xc0229df8 >>>>> >>>>> 0xc0229820 : sub r8, r3, #1 ; 0x1 >>>>> 0xc0229824 : ldr r5, [r7, #4] >>>>> 0xc0229828 : uxth r8, r8 >>>>> 0xc022982c : dmb sy >>>>> >>>>> With GCC 4.6.0: >>>>> 0xc0221630 : cmp r3, #0 ; 0x0 >>>>> 0xc0221634 : beq 0xc0221d7c >>>>> >>>>> 0xc0221638 : cmp r3, r0 >>>>> 0xc022163c : bgt 0xc0221d7c >>>>> >>>>> 0xc0221640 : sub r7, r3, #1 ; 0x1 >>>>> 0xc0221644 : add r3, r11, #16 ; 0x10 >>>>> 0xc0221648 : add r3, r8, r3, lsl #2 >>>>> 0xc022164c : uxth r7, r7 >>>>> 0xc0221650 : ldrb r5, [r3, #5] >>>>> 0xc0221654 : ldrb r2, [r3, #4] >>>>> 0xc0221658 : orr r5, r2, r5, lsl #8 >>>>> 0xc022165c : ldrb r2, [r3, #6] >>>>> 0xc0221660 : ldrb r3, [r3, #7] >>>>> 0xc0221664 : orr r5, r5, r2, lsl #16 >>>>> 0xc0221668 : orr r5, r5, r3, lsl #24 >>>>> 0xc022166c : dmb sy >>>>> >>>>> As you can see, the old compiler accesses the ehci status register >>>>> in a single access, the new compiler dances around and makes multiple >>>>> accesses, which in the end get very incorrect data (I think that this >>>>> register is like many which clear bits on reads). >>>>> >>>>> Any ideas where I can go with this? I'm really trying to keep up with >>>>> Poky/Yocto, but this move to GCC 4.6.0 has broken my ARM targets :-( >>>>> I do have PowerPC targets as well - they seem fine (from limited >>>>> testing) >>>>> with the new compiler. >>>>> >>>>> Note: if you want to see the whole function disassembly, look at >>>>> http://www.mlbassoc.com/poky/ehci_hub_control-disassembly-gcc-4.5.2 >>>>> http://www.mlbassoc.com/poky/ehci_hub_control-disassembly-gcc-4.6.0 >>>>> >>>>> Thanks >>>>> >>> >>> OK. thanks for sending the sample code. >>> Can you add -fstrict-volatile-bitfields option to CFLAGS while >>> compiling this file or even the kernel for test sake ? >>> and see if the problem goes away ? >> >> Sorry, this doesn't seem to make any difference in the generated code. >> Hardly surprising as the register in question is a simple u32, not a >> bitfield. >> > > I reduced the testcase a bit further and it seems the bug is similar to http://gcc.gnu.org/bugzilla/PR45819 > > but a bit different that in this case -fstrict-volatile-bitfields does not help > > a fix for this particular problem is > > diff --git a/include/linux/usb/ehci_def.h b/include/linux/usb/ehci_def.h > index 6563802..b8c1833 100644 > --- a/include/linux/usb/ehci_def.h > +++ b/include/linux/usb/ehci_def.h > @@ -194,7 +194,7 @@ struct ehci_dbg_port { > u32 data47; > u32 address; > #define DBGP_EPADDR(dev, ep) (((dev)<<8)|(ep)) > -} __attribute__ ((packed)); > +} __attribute__ ((packed,aligned(__alignof__(int)))); > > #ifdef CONFIG_EARLY_PRINTK_DBGP > #include > > > since this particular structure all elements are integers but there might be more packed structures which have say char or short ints > and are not necessarily ordered in the descending order of alignment > > Try it out and see if it helps Yes, this does fix the problem :-) The EHCI USB port on the OMAP is working again. Thanks -- ------------------------------------------------------------ Gary Thomas | Consulting for the MLB Associates | Embedded world ------------------------------------------------------------