PCI/ASPM: Fix pci_clear_and_set_config_dword() usage

PCI/ASPM: Fix pci_clear_and_set_config_dword() usage

commit cc33985d26c92a5c908c0185239c59ec35b8637c upstream.

When aspm_calc_l12_info() programs the L1 PM Substates Control 1 register
fields Common_Mode_Restore_Time, LTR_L1.2_THRESHOLD_Value and _Scale, it
invokes pci_clear_and_set_config_dword() in an incorrect way:

For the bits to clear it selects those corresponding to the field.  So far
so good.  But for the bits to set it passes a full register value.
pci_clear_and_set_config_dword() performs a boolean OR operation which
sets all bits of that value, not just the ones that were just cleared.

Thus, when setting the LTR_L1.2_THRESHOLD_Value and _Scale on the child of
an ASPM link, aspm_calc_l12_info() also sets the Common_Mode_Restore_Time.
That's a spec violation:  PCIe r7.0 sec 7.8.3.3 says this field is RsvdP
for Upstream Ports.  On Adrià's Pixelbook Eve, Common_Mode_Restore_Time
of the Intel 7265 "Stone Peak" wifi card is zero, yet aspm_calc_l12_info()
does not preserve the zero bits but instead programs the value calculated
for the Root Port into the wifi card.

Likewise, when setting the Common_Mode_Restore_Time on the Root Port,
aspm_calc_l12_info() also changes the LTR_L1.2_THRESHOLD_Value and _Scale
from the initial 163840 nsec to 237568 nsec (due to ORing those fields),
only to reduce it afterwards to 106496 nsec.

Amend all invocations of pci_clear_and_set_config_dword() to only set bits
which are cleared.

Finally, when setting the T_POWER_ON_Value and _Scale on the Root Port and
the wifi card, aspm_calc_l12_info() fails to preserve bits declared RsvdP
and instead overwrites them with zeroes.  Replace pci_write_config_dword()
with pci_clear_and_set_config_dword() to avoid this.

Fixes: aeda9adebab8 ("PCI/ASPM: Configure L1 substate settings")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=220705#c22
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Adrià Vilanova Martínez <me@avm99963.com>
Cc: stable@vger.kernel.org # v4.11+
Link: https://patch.msgid.link/5c1752d7512eed0f4ea57b84b12d7ee08ca61fc5.1771226659.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>