Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support

From	Mason <slash.tmp@free.fr>
Newsgroups	linux.kernel
Subject	Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support
Date	2017-07-05 02:10 +0200
Message-ID	<tZG3f-74v-7@gated-at.bofh.it> (permalink)
References	(1 earlier) <tUmHV-6aA-27@gated-at.bofh.it> <tYWjL-H8-3@gated-at.bofh.it> <tZ6j7-7MN-11@gated-at.bofh.it> <tZ9TM-2c1-129@gated-at.bofh.it> <tZe6Z-54E-7@gated-at.bofh.it>
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On 03/07/2017 20:11, Russell King - ARM Linux wrote:

> I don't think there's an easy solution to this problem - and I'm not
> sure that stop_machine() can be made to work in this path (which
> needs a process context).  I have a suspicion that the Sigma Designs
> PCI implementation is just soo insane that it's never going to work
> reliably in a multi-SoC kernel without introducing severe performance
> issues for everyone else.

If I remember correctly, this is the second HW block from
tango that has been deemed "too insane for Linux".

The first one was the DMA engine, which doesn't interrupt
when a transfer is done, but when a new transfer may be
programmed. (Though there is a simple work-around for
this one, if we give up command pipelining.)

Do larger SoC vendors have HW devs working closely with
Linux devs, to avoid these design bloopers?

Regards.

Thread

Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Bjorn Helgaas <helgaas@kernel.org> - 2017-07-03 15:50 +0200
  Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Marc Gonzalez <marc_gonzalez@sigmadesigns.com> - 2017-07-03 16:40 +0200
    Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Bjorn Helgaas <helgaas@kernel.org> - 2017-07-04 18:00 +0200
      Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Mason <slash.tmp@free.fr> - 2017-07-05 01:50 +0200
  Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-07-03 20:20 +0200
    Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2017-07-03 20:50 +0200
    Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Bjorn Helgaas <helgaas@kernel.org> - 2017-07-04 17:20 +0200
      Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-07-04 20:20 +0200
    Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Mason <slash.tmp@free.fr> - 2017-07-05 02:10 +0200
      Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-05 07:30 +0200
      Re: [PATCH v9 2/3] PCI: Add tango PCIe host bridge support Mark Brown <broonie@kernel.org> - 2017-07-05 14:40 +0200

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