022b82336a
commit ef61a0405742a9f7f6051bc6fd2f017d87d07911 upstream.
This is a partial revert of 8b3517f88ff2 ("PCI: loongson: Prevent LS7A MRRS
increases") for MIPS-based Loongson.
Some MIPS Loongson systems don't support arbitrary Max_Read_Request_Size
(MRRS) settings. 8b3517f88ff2 ("PCI: loongson: Prevent LS7A MRRS
increases") worked around that by (1) assuming that firmware configured
MRRS to the maximum supported value and (2) preventing the PCI core from
increasing MRRS.
Unfortunately, some firmware doesn't set that maximum MRRS correctly, which
results in devices not being initialized correctly. One symptom, from the
Debian report below, is this:
ata4.00: exception Emask 0x0 SAct 0x20000000 SErr 0x0 action 0x6 frozen
ata4.00: failed command: WRITE FPDMA QUEUED
ata4.00: cmd 61/20:e8:00:f0:e1/00:00:00:00:00/40 tag 29 ncq dma 16384 out
res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
ata4.00: status: { DRDY }
ata4: hard resetting link
Limit MRRS to 256 because MIPS Loongson with higher MRRS support is
considered rare.
This must be done at device enablement stage because the MRRS setting may
get lost if PCI_COMMAND_MASTER on the parent bridge is cleared, and we are
only sure parent bridge is enabled at this point.
Fixes: 8b3517f88ff2 ("PCI: loongson: Prevent LS7A MRRS increases")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217680
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1035587
Link: https://lore.kernel.org/r/20231201115028.84351-1-jiaxun.yang@flygoat.com
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.