| Message ID | 20200430080625.26070-3-pali@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | PCI: aardvark: Fix support for Turris MOX and Compex wifi cards | expand |
On Thu, 30 Apr 2020 10:06:15 +0200, =?UTF-8?q?Pali=20Roh=C3=A1r?= wrote: > Trying to change Link Status register does not have any effect as this > is a read-only register. Trying to overwrite bits for Negotiated Link > Width does not make sense. > > In future proper change of link width can be done via Lane Count Select > bits in PCIe Control 0 register. > > Trying to unconditionally enable ASPM L0s via ASPM Control bits in Link > Control register is wrong. There should be at least some detection if > endpoint supports L0s as isn't mandatory. > > Moreover ASPM Control bits in Link Control register are controlled by > pcie/aspm.c code which sets it according to system ASPM settings, > immediately after aardvark driver probes. So setting these bits by > aardvark driver has no long running effect. > > Remove code which touches ASPM L0s bits from this driver and let > kernel's ASPM implementation to set ASPM state properly. > > Some users are reporting issues that this code is problematic for some > Intel wifi cards and removing it fixes them, see e.g.: > https://bugzilla.kernel.org/show_bug.cgi?id=196339 > > If problems with Intel wifi cards occur even after this commit, then > pcie/aspm.c code could be modified / hooked to not enable ASPM L0s state > for affected problematic cards. > > Signed-off-by: Pali Rohár <pali@kernel.org> > --- > drivers/pci/controller/pci-aardvark.c | 4 ---- > 1 file changed, 4 deletions(-) > Acked-by: Rob Herring <robh@kernel.org>
diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c index f9955b494267..74b90940a9d4 100644 --- a/drivers/pci/controller/pci-aardvark.c +++ b/drivers/pci/controller/pci-aardvark.c @@ -356,10 +356,6 @@ static void advk_pcie_setup_hw(struct advk_pcie *pcie) advk_pcie_wait_for_link(pcie); - reg = PCIE_CORE_LINK_L0S_ENTRY | - (1 << PCIE_CORE_LINK_WIDTH_SHIFT); - advk_writel(pcie, reg, PCIE_CORE_LINK_CTRL_STAT_REG); - reg = advk_readl(pcie, PCIE_CORE_CMD_STATUS_REG); reg |= PCIE_CORE_CMD_MEM_ACCESS_EN | PCIE_CORE_CMD_IO_ACCESS_EN |
Trying to change Link Status register does not have any effect as this is a read-only register. Trying to overwrite bits for Negotiated Link Width does not make sense. In future proper change of link width can be done via Lane Count Select bits in PCIe Control 0 register. Trying to unconditionally enable ASPM L0s via ASPM Control bits in Link Control register is wrong. There should be at least some detection if endpoint supports L0s as isn't mandatory. Moreover ASPM Control bits in Link Control register are controlled by pcie/aspm.c code which sets it according to system ASPM settings, immediately after aardvark driver probes. So setting these bits by aardvark driver has no long running effect. Remove code which touches ASPM L0s bits from this driver and let kernel's ASPM implementation to set ASPM state properly. Some users are reporting issues that this code is problematic for some Intel wifi cards and removing it fixes them, see e.g.: https://bugzilla.kernel.org/show_bug.cgi?id=196339 If problems with Intel wifi cards occur even after this commit, then pcie/aspm.c code could be modified / hooked to not enable ASPM L0s state for affected problematic cards. Signed-off-by: Pali Rohár <pali@kernel.org> --- drivers/pci/controller/pci-aardvark.c | 4 ---- 1 file changed, 4 deletions(-)