kenwong at marvell
May 23, 2012, 4:49 PM
Post #1 of 1
FW: Loading PCIe Device Driver at Dom0
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.
What the driver does:
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) &&
if (request_irq(dev->irq, func_msi_interrupt, IRQF_SHARED, DRIVER_NAME, my_dev))
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
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.
Thanks a lot in advance!!