On Thu, Aug 29, 2019 at 4:33 PM Dan Williams <dan.j.williams@xxxxxxxxx> 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. > > Reported-by: Stephen Douthit <stephend@xxxxxxxxxxxxxxx> > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> > --- > Changes since v1 [1]: > - Find a way to not duplicate a large portion of the ahci_pci_tbl[] > array (Stephen). > - Add a definition for the PCS register offset rather than hard code > (Stephen) > > [1]: https://lore.kernel.org/r/a04c0ae7-ef4d-4275-de05-b74beaeef86c@xxxxxxxxxxxxxxx/ > > drivers/ata/ahci.c | 70 ++++++++++++++++++++++++++++++++-------------------- > drivers/ata/ahci.h | 2 + > 2 files changed, 45 insertions(+), 27 deletions(-) > > diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c > index f7652baa6337..847e3796d505 100644 > --- a/drivers/ata/ahci.c > +++ b/drivers/ata/ahci.c > @@ -65,6 +65,12 @@ enum board_ids { > board_ahci_sb700, /* for SB700 and SB800 */ > board_ahci_vt8251, > > + /* > + * board IDs for Intel chipsets that support more than 6 ports > + * *and* end up needing the PCS quirk. > + */ Ugh, sorry, I just realized I did not opt Denverton out of this... v3 on the way.
