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Re: Regarding AHCI_MAX_SG and (ATA_HORKAGE_MAX_SEC_1024)

From David Milburn <dmilburn@redhat.com>
Newsgroups linux.kernel
Subject Re: Regarding AHCI_MAX_SG and (ATA_HORKAGE_MAX_SEC_1024)
Date 2016-08-10 21:40 +0200
Message-ID <s4Hw7-YV-59@gated-at.bofh.it> (permalink)
References (1 earlier) <s4sno-88Q-25@gated-at.bofh.it> <s4G72-8uN-149@gated-at.bofh.it> <s4G72-8uN-151@gated-at.bofh.it> <s4G72-8uN-147@gated-at.bofh.it> <s4Hw7-YV-61@gated-at.bofh.it>
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On 08/10/2016 12:19 PM, Tom Yan wrote:
> 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
>

Yes, but in both cases mem_dma gets adjusted for AHCI_CMD_SLOT_SZ (1024)
and rx_fis_sz (256 or 4096 in fbs case).

Thanks,
David

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Thread

Regarding AHCI_MAX_SG and (ATA_HORKAGE_MAX_SEC_1024) Tom Yan <tom.ty89@gmail.com> - 2016-08-07 16:20 +0200
  Re: Regarding AHCI_MAX_SG and (ATA_HORKAGE_MAX_SEC_1024) Tejun Heo <tj@kernel.org> - 2016-08-10 05:30 +0200
    Re: Regarding AHCI_MAX_SG and (ATA_HORKAGE_MAX_SEC_1024) David Milburn <dmilburn@redhat.com> - 2016-08-10 20:10 +0200
      Re: Regarding AHCI_MAX_SG and (ATA_HORKAGE_MAX_SEC_1024) David Milburn <dmilburn@redhat.com> - 2016-08-10 21:40 +0200
      Re: Regarding AHCI_MAX_SG and (ATA_HORKAGE_MAX_SEC_1024) Tom Yan <tom.ty89@gmail.com> - 2016-08-10 22:20 +0200
    Re: Regarding AHCI_MAX_SG and (ATA_HORKAGE_MAX_SEC_1024) Tejun Heo <tj@kernel.org> - 2016-08-10 21:10 +0200
    Re: Regarding AHCI_MAX_SG and (ATA_HORKAGE_MAX_SEC_1024) Tom Yan <tom.ty89@gmail.com> - 2016-08-10 21:20 +0200

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