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Bjorn Helgaas
7afeb84d14
80d7d7a904("PCI/ASPM: Calculate LTR_L1.2_THRESHOLD from device characteristics") replaced a fixed value (163840ns) with one computed from T_POWER_OFF, Common_Mode_Restore_Time, etc., but it encoded the LTR_L1.2_THRESHOLD value incorrectly. This is especially a problem for small thresholds, e.g., 63ns fell into the "threshold_ns < 1024" case and was encoded as 32ns: LTR_L1.2_THRESHOLD_Scale = 1 (multiplier is 32ns) LTR_L1.2_THRESHOLD_Value = 63 >> 5 = 1 LTR_L1.2_THRESHOLD = multiplier * value = 32ns * 1 = 32ns Correct the algorithm to encode all times of 1023ns (0x3ff) or smaller exactly and larger times conservatively (the encoded threshold is never smaller than was requested). This reduces the chance of entering L1.2 when the device can't tolerate the exit latency. Fixes:80d7d7a904("PCI/ASPM: Calculate LTR_L1.2_THRESHOLD from device characteristics") Link: https://lore.kernel.org/r/20221005025809.2247547-4-helgaas@kernel.org Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.