Re: [Xen-devel] Loading PCIe Device Driver at Dom0

[Kenneth Wong <kenwong@xxxxxxxxxxx>]

Hi all,

I am now using dma_alloc_coherent().

However, the first parameter, pdev->dev required, which is "struct device", 
does not seem to have initialized.  

When and who is suppose to initialize it?

In Linux, I can pass "NULL" and it just works.  In Xen, it crashes.  

Sometimes insmod pass, sometimes hangs the system.

Please advise!

Kenneth
________________________________________
From: Pasi Kärkkäinen [pasik@xxxxxx]
Sent: Wednesday, May 23, 2012 11:18 PM
To: Kenneth Wong
Cc: xen-devel@xxxxxxxxxxxxx
Subject: Re: [Xen-devel] Loading PCIe Device Driver at Dom0

On Wed, May 23, 2012 at 07:41:34PM -0700, Kenneth Wong wrote:
> Hi Konrad and others,
>
> Oh, there are Xen/dom0 specific APIs for PCI and DMA?
>

PCI/DMA APIs are the Linux kernel APIs, not Xen specific.


> May I ask the names and where can I can more info on the APIs?
>

Quick googling reveals:

http://www.mjmwired.net/kernel/Documentation/DMA-API.txt
http://www.mjmwired.net/kernel/Documentation/DMA-API-HOWTO.txt


-- Pasi

> Many thanks!
>
> Kenneth
>
> ________________________________________
> From: Konrad Rzeszutek Wilk [konrad.wilk@xxxxxxxxxx]
> Sent: Wednesday, May 23, 2012 5:17 PM
> To: Kenneth Wong
> Cc: xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Loading PCIe Device Driver at Dom0
>
> On Wed, May 23, 2012 at 04:43:55PM -0700, Kenneth Wong wrote:
> > Dear all,
> >
> > I have a PCIe device driver that I have been using on various Linux 
> > distributions and Kernel versions (2.6.x - 3.x.y) successfully all along.
> >
> > I recently set up a Xen environment with Linux Mint 12 and Xen Hypervisor 
> > 4.1.  When I boot to Linux Mint, my driver still load (via insmod manually) 
> > successfully at Dom0 without any issue.  I can do reads and write to the 
> > hardware device.  But once booted to Xen, the driver failed to complete the 
> > driver load (via insmod manually) at Dom 0 and the console just hangs.
> >
> > >From my debug messages, it appears it hangs because the driver doesn't 
> > >receive any interrupt after a command is sent to the hardware device by 
> > >writing a parameter to the mapped register.  Once that register is 
> > >written, the device is expected to DMA the command from the buffer 
> > >allocated by the driver.
> >
> > The things that I can only think of that might have caused the problem are 
> > 1) IRQ mapping issue, or 2) DMA mapping issue, which I am not sure.
>
> The 2).
> >
> >
> > What the driver does:
>
> You do need to use the PCI API (or the DMA API).
>
> >
> > Set up a command buffer:
> > Buf_t *buf = kmalloc(BUF_SIZE*sizeof(buf_t), GFP_KERNEL);
> > unsigned long buf_addr = __pa(buf);
> > unsigned int buf_addr_low = (unsigned int)buf_addr;
> >
> > Tell device about the buffer:
> > iowrite32(buf_addr_low, dev->pci_reg_map + BUF_ADR__LOW);
>
> >
> > Set up IRQ:
> >     if (pci_find_capability(dev, PCI_CAP_ID_MSI) &&
> >         (!pci_enable_msi(dev)))
> >     {
> >         if (request_irq(dev->irq, func_msi_interrupt, IRQF_SHARED, 
> > DRIVER_NAME, my_dev))
> >         {
> >             return  -ENODEV;
> >         }
> >         my_dev->intr_mode = INTERRUPT_MSI;
> >     }
> >
> > Ask device to fetch command from buffer (Expect interrupt after this after 
> > device fetched the command from buf.  But interrupt did not happen.):
> > iowrite32(buf_offset, dev->pci_reg_map + FETCH_CMD_REG);
> >
> >
> > >From dmesg, it looks like IRQ initialization is complete.
> > [  241.743769] My_driver initialization
> > [  241.743787] xen: registering gsi 16 triggering 0 polarity 1
> > [  241.743793] xen_map_pirq_gsi: returning irq 16 for gsi 16
> > [  241.743795] xen: --> pirq=16 -> irq=16 (gsi=16)
> > [  241.743801] Already setup the GSI :16
> > [  241.743805] my-driver 0000:02:00.0: PCI INT A -> GSI 16 (level, low) -> 
> > IRQ 16
> > [  241.743815] my-driver 0000:02:00.0: setting latency timer to 64
> >
> > /proc/interrupts:
> >             CPU0       CPU1       CPU2       CPU3       CPU4       CPU5     
> >   CPU6       CPU7
> > ......
> > ......
> > 339:          0          0          0          0          0          0      
> >     0          0  xen-pirq-msi       my-driver
> > ......
> > ......
> >
> > Any idea what might cause the problem?
> >
> > Is there anything we have to be enable/disable, use different functions, or 
> > do differently in drivers written for Xen Dom0 environment regarding the 
> > following?
> > 1)       Allocating a DMA buffer in driver to allow the device to DMA 
> > stuffs.
> > 2)       Requesting MSI irq.
> >
> > Please advise!
> >
> > Thanks a lot in advance!!
> >
> > Kenneth
>
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel

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