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Date: Thu, 15 Aug 2013 10:54:28 -0700
From: Guenter Roeck <linux@roeck-us.net>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
        Paul Gortmaker <paul.gortmaker@windriver.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        QEMU Developers <qemu-devel@nongnu.org>,
        Arnd Bergmann <arnd.bergmann@linaro.org>
Subject: Re: [Qemu-devel] SCSI bus failures with qemu-arm in kernel 3.8+
Message-ID: <20130815175428.GA18580@roeck-us.net>
References: <5207B3C3.9080508@roeck-us.net>
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On Thu, Aug 15, 2013 at 05:45:42PM +0100, Peter Maydell wrote:
> On 13 August 2013 04:40, Guenter Roeck <linux@roeck-us.net> wrote:
> > Patch tested and working with qemu 1.5.2, using the configuration file
> > from the yocto project. Patch applied on top of kernel version 3.11-rc5.
> 
> OK, I tested this on PB926+PCI backplane hardware, and it is
> definitely better than current mainline, in that the test USB
> card that I have no longer causes the kernel to generate this sort of
> backtrace:
> 
Do you mean my patch fixes the traceback below as a side effect ?
Would be great ... it would be one more reason to get it applied.

> ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
> ehci-pci: EHCI PCI platform driver
> ehci-pci 0000:00:1e.2: EHCI Host Controller
> ehci-pci 0000:00:1e.2: new USB bus registered, assigned bus number 1
> ehci-pci 0000:00:1e.2: irq 91, io mem 0x50002000
> ehci-pci 0000:00:1e.2: USB 2.0 started, EHCI 1.00
> usb usb1: New USB device found, idVendor=1d6b, idProduct=0002
> usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
> usb usb1: Product: EHCI Host Controller
> usb usb1: Manufacturer: Linux 3.10.0+ ehci_hcd
> usb usb1: SerialNumber: 0000:00:1e.2
> hub 1-0:1.0: USB hub found
> hub 1-0:1.0: 3 ports detected
> ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
> ohci-pci: OHCI PCI platform driver
> ohci-pci 0000:00:1e.0: OHCI PCI host controller
> ohci-pci 0000:00:1e.0: new USB bus registered, assigned bus number 2
> irq 93: nobody cared (try booting with the "irqpoll" option)
> CPU: 0 PID: 1 Comm: swapper Not tainted 3.10.0+ #9
> [<c00187d4>] (unwind_backtrace+0x0/0xf0) from [<c0015b48>]
> (show_stack+0x10/0x14)
> [<c0015b48>] (show_stack+0x10/0x14) from [<c0054cac>]
> (__report_bad_irq+0x24/0xb8)
> [<c0054cac>] (__report_bad_irq+0x24/0xb8) from [<c005511c>]
> (note_interrupt+0x1cc/0x230)
> [<c005511c>] (note_interrupt+0x1cc/0x230) from [<c005363c>]
> (handle_irq_event_percpu+0xac/0x1c4)
> [<c005363c>] (handle_irq_event_percpu+0xac/0x1c4) from [<c005377c>]
> (handle_irq_event+0x28/0x38)
> [<c005377c>] (handle_irq_event+0x28/0x38) from [<c00558c8>]
> (handle_level_irq+0x80/0xd4)
> [<c00558c8>] (handle_level_irq+0x80/0xd4) from [<c0052fb4>]
> (generic_handle_irq+0x2c/0x40)
> [<c0052fb4>] (generic_handle_irq+0x2c/0x40) from [<c016bf38>]
> (fpga_irq_handle+0x3c/0x50)
> [<c016bf38>] (fpga_irq_handle+0x3c/0x50) from [<c0052fb4>]
> (generic_handle_irq+0x2c/0x40)
> [<c0052fb4>] (generic_handle_irq+0x2c/0x40) from [<c0013e8c>]
> (handle_IRQ+0x30/0x84)
> [<c0013e8c>] (handle_IRQ+0x30/0x84) from [<c0008750>] (vic_handle_irq+0x5c/0x9c)
> [<c0008750>] (vic_handle_irq+0x5c/0x9c) from [<c00165c0>] (__irq_svc+0x40/0x4c)
> Exception stack(0xc7829cc8 to 0xc7829d10)
> 9cc0:                   00000001 0000000a 00000100 20000013 00000002 00000024
> 9ce0: c7828000 c0476980 3fb96c1c c0443950 c04693c0 00000001 c0456a50 c7829d10
> 9d00: c0025f38 c0025fa8 20000013 ffffffff
> [<c00165c0>] (__irq_svc+0x40/0x4c) from [<c0025fa8>] (__do_softirq+0x80/0x1b4)
> [<c0025fa8>] (__do_softirq+0x80/0x1b4) from [<c00263a4>] (irq_exit+0x54/0x90)
> [<c00263a4>] (irq_exit+0x54/0x90) from [<c0013e90>] (handle_IRQ+0x34/0x84)
> [<c0013e90>] (handle_IRQ+0x34/0x84) from [<c0008750>] (vic_handle_irq+0x5c/0x9c)
> [<c0008750>] (vic_handle_irq+0x5c/0x9c) from [<c00165c0>] (__irq_svc+0x40/0x4c)
> Exception stack(0xc7829d80 to 0xc7829dc8)
> 9d80: 00000000 0000005d 20000000 00000000 c79bb7e0 c0446990 60000013 c79c0000
> 9da0: 0000005d 00000000 c04469c4 00000001 00000000 c7829dc8 c00555c8 c0054460
> 9dc0: 40000013 ffffffff
> [<c00165c0>] (__irq_svc+0x40/0x4c) from [<c0054460>] (__setup_irq+0x1f4/0x3f0)
> [<c0054460>] (__setup_irq+0x1f4/0x3f0) from [<c00548ac>]
> (request_threaded_irq+0xb4/0x138)
> [<c00548ac>] (request_threaded_irq+0xb4/0x138) from [<c01fa7a8>]
> (usb_add_hcd+0x4f0/0x6f0)
> [<c01fa7a8>] (usb_add_hcd+0x4f0/0x6f0) from [<c0206bdc>]
> (usb_hcd_pci_probe+0x200/0x36c)
> [<c0206bdc>] (usb_hcd_pci_probe+0x200/0x36c) from [<c017467c>]
> (pci_device_probe+0x68/0x90)
> [<c017467c>] (pci_device_probe+0x68/0x90) from [<c01b3a80>]
> (driver_probe_device+0x78/0x200)
> [<c01b3a80>] (driver_probe_device+0x78/0x200) from [<c01b3c94>]
> (__driver_attach+0x8c/0x90)
> [<c01b3c94>] (__driver_attach+0x8c/0x90) from [<c01b2288>]
> (bus_for_each_dev+0x58/0x88)
> [<c01b2288>] (bus_for_each_dev+0x58/0x88) from [<c01b29e8>]
> (bus_add_driver+0xd8/0x220)
> [<c01b29e8>] (bus_add_driver+0xd8/0x220) from [<c01b4258>]
> (driver_register+0x78/0x144)
> [<c01b4258>] (driver_register+0x78/0x144) from [<c0410820>]
> (do_one_initcall+0x94/0x154)
> [<c0410820>] (do_one_initcall+0x94/0x154) from [<c04109cc>]
> (kernel_init_freeable+0xec/0x1b0)
> [<c04109cc>] (kernel_init_freeable+0xec/0x1b0) from [<c0323104>]
> (kernel_init+0x8/0xe4)
> [<c0323104>] (kernel_init+0x8/0xe4) from [<c00130b0>] (ret_from_fork+0x14/0x24)
> handlers:
> [<c01f7e48>] usb_hcd_irq
> Disabling IRQ #93
> 
> However it still doesn't seem to reliably detect the USB harddisk
> plugged into the card, so I think there may be further issues, possibly
> some subset of those Arnd identified and fixed with this patch:
> http://permalink.gmane.org/gmane.linux.ports.arm.kernel/93397
> 
Does it get better if you apply Arnd's patch ?

> so I'd like to continue testing.
> 
> The other thing this patch should (IMHO) have is the
> line in pci_versatile_setup() which tells QEMU that the
> kernel really does expect hardware-like behaviour:
> 
> --- a/arch/arm/mach-versatile/pci.c
> +++ b/arch/arm/mach-versatile/pci.c
> @@ -295,6 +295,19 @@ int __init pci_versatile_setup(int nr, struct
> pci_sys_data *sys)
>         __raw_writel(PHYS_OFFSET, local_pci_cfg_base + PCI_BASE_ADDRESS_2);
> 
>         /*
> +        * For many years the kernel and QEMU were symbiotically buggy
> +        * in that they both assumed the same broken IRQ mapping.
> +        * QEMU therefore attempts to auto-detect old broken kernels
> +        * so that they still work on newer QEMU as they did on old
> +        * QEMU. Since we now use the correct (ie matching-hardware)
> +        * IRQ mapping we write a definitely different value to a
> +        * PCI_INTERRUPT_LINE register to tell QEMU that we expect
> +        * real hardware behaviour and it need not be backwards
> +        * compatible for us. This write is harmless on real hardware.
> +        */
> +       __raw_writel(0, VERSATILE_PCI_VIRT_BASE+PCI_INTERRUPT_LINE);
> +
> +       /*
>          * Do not to map Versatile FPGA PCI device into memory space
>          */
>         pci_slot_ignore |= (1 << myslot);
> 
> I appreciate that QEMU-specific code in the kernel is a bit ugly, but
> (a) 99.9% of the people running this code are going to be running it on QEMU
> (b) the bugs in this area have been extremely long-standing in both
> the kernel and QEMU and so there are a lot of legacy kernel images
> out there that worked just fine with QEMU
> (c) it's rather less code than I have in QEMU as the QEMU-side part
> of this backwards-compatibility autodetection.
> 
> (Without this line QEMU will guess whether the kernel is broken
> or not and will get it right most but not necessarily all of the time.)
> 
Might make sense, but I think it should be a separate patch.

If I understand correctly, my patch fixes the SCSI problem.
Is that correct ? If so, can we get it applied to mainline ?

Thanks,
Guenter
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