From: Pali Rohár pali@kernel.org
[ Upstream commit 90c6cb4a355e7befcb557d217d1d8b8bd5875a05 ]
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.
Link: https://lore.kernel.org/r/20200430080625.26070-3-pali@kernel.org Tested-by: Tomasz Maciej Nowak tmn505@gmail.com Signed-off-by: Pali Rohár pali@kernel.org Signed-off-by: Lorenzo Pieralisi lorenzo.pieralisi@arm.com Acked-by: Rob Herring robh@kernel.org Acked-by: Thomas Petazzoni thomas.petazzoni@bootlin.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pci/host/pci-aardvark.c | 4 ---- 1 file changed, 4 deletions(-)
diff --git a/drivers/pci/host/pci-aardvark.c b/drivers/pci/host/pci-aardvark.c index 1dbd09c91a7c..736d9f58438e 100644 --- a/drivers/pci/host/pci-aardvark.c +++ b/drivers/pci/host/pci-aardvark.c @@ -363,10 +363,6 @@ 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 |