Re: Addresses in PxCLB and PxCLBU

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Hello.

On 7/7/2015 2:41 AM, Andy Falanga (afalanga) wrote:

> I'm working with the registers in an AHCI controller.  The memory
> address contained in PxCLB and PxCLBU (if 64-bit addressing is
> supported): what kind of address are they?

    Apparently, physical. The hardware only operates on the physical addresses.

> Currently, when I get the
> address and place it into a pointer of struct ahci_cmd_hdr and try to
> dereference, my VM locks and then reboots.  What am I doing incorrectly?

    You can't de-reference physical addresses.

> Basically, I have this:

> void __iomem * pbase = ahci_port_base((struct ata_port*));

    Can't parse this.

> struct ahci_cmd_hdr *cmd_hdr = NULL;

> cmd_hdr = (struct ahci_cmd_hdr*)(u64)
>      ((u64)(*(temp + PORT_LST_ADDR_HI)) << 32 | *temp);

   temp?

> pr_info("cmd_hdr is %p\n", cmd_hdr);
> pr_info("cmd_hdr->opts is %d\n", cmd_hdr->opts);  /* opts is __le32 */

> At the last line above my VM hangs and reboots.  The memory address is
> something like 0x0000000037900000.  This address makes me think that I
> simply can't dereference it but I'm quite new to this and I don't know
> what I should do.  I'd appreciate any help even if that's a pointer (no
> pun intended) to a more appropriate forum.

    The corresponding virtual address seems to be contained in 
ahci_port_priv::cmd_slot.

> Thanks,
> Andy

WBR, Sergei