lkml.org 
[lkml]   [2019]   [Aug]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v3] libata/ahci: Drop PCS quirk for Denverton and beyond
From
Date
On 8/29/19 5:30 PM, Dan Williams wrote:
> The Linux ahci driver has historically implemented a configuration fixup
> for platforms / platform-firmware that fails to enable the ports prior
> to OS hand-off at boot. The fixup was originally implemented way back
> before ahci moved from drivers/scsi/ to drivers/ata/, and was updated in
> 2007 via commit 49f290903935 "ahci: update PCS programming". The quirk
> sets a port-enable bitmap in the PCS register at offset 0x92.
>
> This quirk could be applied generically up until the arrival of the
> Denverton (DNV) platform. The DNV AHCI controller architecture supports
> more than 6 ports and along with that the PCS register location and
> format were updated to allow for more possible ports in the bitmap. DNV
> AHCI expands the register to 32-bits and moves it to offset 0x94.
>
> As it stands there are no known problem reports with existing Linux
> trying to set bits at offset 0x92 which indicates that the quirk is not
> applicable. Likely it is not applicable on a wider range of platforms,
> but it is difficult to discern which platforms if any still depend on
> the quirk.
>
> Rather than try to fix the PCS quirk to consider the DNV register layout
> instead require explicit opt-in. The assumption is that the OS driver
> need not touch this register, and platforms can be added with a new
> boad_ahci_pcs7 board-id when / if problematic platforms are found in the
> future. The logic in ahci_intel_pcs_quirk() looks for all Intel AHCI
> instances with "legacy" board-ids and otherwise skips the quirk if the
> board was matched by class-code.

Applied, thanks Dan.

--
Jens Axboe

\
 
 \ /
  Last update: 2019-08-31 04:54    [W:0.073 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site