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SubjectRe: Regarding AHCI_MAX_SG and (ATA_HORKAGE_MAX_SEC_1024)
On 10 August 2016 at 15:41, David Milburn <dmilburn@redhat.com> wrote:
> Hi,
>
> The 168 makes AHCI_CMD_TBL_SZ equal to 2816
>
> AHCI_CMD_TBL_SZ = AHCI_CMD_TBL_HDR_SZ + (AHCI_MAX_SG * 16)
> AHCI_CMD_TBL_SZ = 128 + (168 * 16)
>
> I think if you add in AHCI_CMD_SLOT_SZ (1024) and AHCI_RX_FIS_SZ (256)
> the DMA is 4K aligned, I think that is where the 168 came from.

Looks like the right guess. Though AHCI_PORT_PRIV_DMA_SZ is not:

AHCI_CMD_SLOT_SZ (1024) + AHCI_CMD_TBL_SZ (2816) + AHCI_RX_FIS_SZ (256) = 4096

but:

AHCI_CMD_SLOT_SZ (1024) + AHCI_CMD_TBL_AR_SZ (2816 * 32 = 90112) +
AHCI_RX_FIS_SZ (256) = 91392

and AHCI_PORT_PRIV_FBS_DMA_SZ is:

AHCI_CMD_SLOT_SZ (1024) + AHCI_CMD_TBL_AR_SZ (2816 * 32 = 90112) +
AHCI_RX_FIS_SZ * 16 (4096) = 95232

>
> Thanks,
> David
>
>

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