From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Subject: Re: [PATCH 2/2] PCI: Stop clearing bridge Secondary Status when setting up I/O aperture
Date: Mon, 9 Dec 2013 12:33:32 -0700 [thread overview]
Message-ID: <20131209193332.GB20199@obsidianresearch.com> (raw)
In-Reply-To: <20131206001954.27659.78163.stgit@bhelgaas-glaptop.roam.corp.google.com>
On Thu, Dec 05, 2013 at 05:19:55PM -0700, Bjorn Helgaas wrote:
> pci_setup_bridge_io() accessed PCI_IO_BASE and PCI_IO_LIMIT using dword
> (32-bit) reads and writes, which also access the Secondary Status register.
> Since the Secondary Status register is in the upper 16 bits of the dword,
> and we preserved those upper 16 bits, this had the effect of clearing any
> of the write-1-to-clear bits that happened to be set in the Secondary
> Status register.
This is a good catch!
> - pci_write_config_dword(bridge, PCI_IO_BASE, l);
> + pci_write_config_word(bridge, PCI_IO_BASE, l);
But this is a problem :(
tegra and mvebu at least do not have HW to do non-32 bit writes, so
their implementation of pci_write_config_word does the RMW internally
and will still have this same bug.
I think you have to keep the 32 bit write here, but zero the
write-one-to-clear bits :(
Regards,
Jason
next prev parent reply other threads:[~2013-12-09 19:33 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-06 0:19 [PATCH 0/2] Bridge window discovery and setup fixes Bjorn Helgaas
2013-12-06 0:19 ` [PATCH 1/2] PCI: Prevent bus conflicts while checking for bridge apertures Bjorn Helgaas
2013-12-09 19:31 ` Jason Gunthorpe
2013-12-09 20:00 ` Bjorn Helgaas
2013-12-09 20:15 ` Jason Gunthorpe
2013-12-06 0:19 ` [PATCH 2/2] PCI: Stop clearing bridge Secondary Status when setting up I/O aperture Bjorn Helgaas
2013-12-09 19:33 ` Jason Gunthorpe [this message]
2013-12-09 20:15 ` Bjorn Helgaas
2013-12-09 21:27 ` Jason Gunthorpe
2013-12-09 21:58 ` Bjorn Helgaas
2013-12-10 0:10 ` Jason Gunthorpe
2013-12-10 0:18 ` Bjorn Helgaas
2013-12-10 1:31 ` Jason Gunthorpe
2013-12-10 18:22 ` Bjorn Helgaas
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