On Fri, Oct 01, 2021 at 08:21:06PM +0530, Ajay Garg wrote:
> Hi All.
>
> I have a SD/MMC reader over PCI, which displays the following (amongst
> others) when we do "lspci -vv" :
>
> #########################################################
> Region 0: Memory at e2c20000 (32-bit, non-prefetchable) [size=512]
> #########################################################
>
> Above shows that e2c20000 is the physical (base-)address of BAR0.
>
> Now, in the device driver, I do the following :
>
> ########################################################
> .....
> struct pci_dev *ptr;
> void __iomem *bar0_ptr;
> ......
>
> ......
> pci_request_region(ptr, 0, "ajay_sd_mmc_BAR0_region");
> bar0_ptr = pci_iomap(ptr, 0, pci_resource_len(ptr, 0));
>
> printk("Base virtual-address = [%p]\n", bar0_ptr);
> printk("Base physical-address = [%p]\n", virt_to_phys(bar0_ptr));
> printk("Base bus-address = [%p]\n", virt_to_bus(bar0_ptr));
>
> I have removed error-checking, but I confirm that pci_request_region()
> and pci_iomap calls are successful.
>
> Now, in the 3 printk's, none of the value is printed as e2c20000.
> I was expecting that the 2nd result, of virt_to_phys() translation,
> would be equal to the base-address of BAR0 register, as reported by
> lspci.
>
>
> What am I missing?
> Will be grateful for pointers.
The CPU address isn't always the same as the PCI address. For example,
some memory resources are added via pci_add_resource_offset(), so the
windows the host sees will be different than the ones the devices use.
