From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by mx1.pokylinux.org (Postfix) with ESMTP id C39264C800B6 for ; Thu, 9 Jun 2011 17:33:48 -0500 (CDT) Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga101.jf.intel.com with ESMTP; 09 Jun 2011 15:33:48 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.65,343,1304319600"; d="scan'208";a="11603232" Received: from doubt.jf.intel.com (HELO [10.7.199.145]) ([10.7.199.145]) by orsmga002.jf.intel.com with ESMTP; 09 Jun 2011 15:33:48 -0700 Message-ID: <4DF14A49.6000104@linux.intel.com> Date: Thu, 09 Jun 2011 15:33:45 -0700 From: Darren Hart User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110424 Lightning/1.0b2 Thunderbird/3.1.10 MIME-Version: 1.0 To: Gary Thomas References: <4DEFB4BA.7050902@mlbassoc.com> <4DEFBD77.7000400@linux.intel.com> <4DF016F0.4080106@gmail.com> <4DF02EDF.5040502@mlbassoc.com> <4DF06CB0.1040501@gmail.com> <4DF0AC87.2060901@mlbassoc.com> <4DF0AF61.1020108@mlbassoc.com> In-Reply-To: <4DF0AF61.1020108@mlbassoc.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 22:33:49 -0000 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit On 06/09/2011 04:32 AM, Gary Thomas wrote: > On 06/09/2011 05:20 AM, Gary Thomas wrote: >> 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. > > Note: it also works properly if the __attribute__ ((packed)) is simply removed. > Looking at the layout of this structure, I don't see what that attribute is > trying to accomplish - every item within the structure is u32[], so IMO there > is nothing to pack. Perhaps this observation can help the GCC folks figure > out why things are getting confused. I tried each of these and neither worked. I confirmed the kernel was indeed different after each build and that gcc 4.6.0 was being used (by adding CC --version to the kernel do_compile and checking it in the log). Gary, are you certain that you were building with 4.6.0 ? I've found it to be a bit tricky to switch back and forth between compilers. -- Darren Hart Intel Open Source Technology Center Yocto Project - Linux Kernel