mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-05 11:01:06 -04:00
ee91cb570d
While the Apple PCIe driver works correctly when directly booted from the
firmware, it fails to initialise when the kernel is booted from a
bootloader using PCIe such as u-boot.
That's because we're missing a proper reset of the port (we only clear the
reset, but never assert it).
The PCIe spec requirements are two-fold:
- PERST# must be asserted before setting up the clocks and stay asserted
for at least 100us (Tperst-clk)
- Once PERST# is deasserted, the OS must wait for at least 100ms "from
the end of a Conventional Reset" before we can start talking to the
devices
Implementing this results in a booting system.
[bhelgaas: #PERST -> PERST#, update spec references to current]
Fixes: 1e33888fbe ("PCI: apple: Add initial hardware bring-up")
Link: https://lore.kernel.org/r/20211123180636.80558-2-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
Acked-by: Pali Rohár <pali@kernel.org>
Cc: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.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.