linux-kernel - Re: [PATCH v3 0/5] PCI: mt7621: Remove specific MIPS code from driver

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Date:   Wed, 12 Jan 2022 15:52:03 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Sergio Paracuellos <sergio.paracuellos@...il.com>
Cc:     linux-pci@...r.kernel.org, tsbogend@...ha.franken.de,
        lorenzo.pieralisi@....com, bhelgaas@...gle.com, linux@...ck-us.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/5] PCI: mt7621: Remove specific MIPS code from driver

On Tue, Dec 07, 2021 at 11:49:19AM +0100, Sergio Paracuellos wrote:
> Hi all,
> 
> MIPS specific code can be removed from driver and put into ralink mt7621
> instead which is a more accurate place to do this. To make this possible
> we need to have access to 'bridge->windows' in 'pcibios_root_bridge_prepare()'
> which has been implemented for ralink mt7621 platform (there is no real
> need to implement this for any other platforms since those ones haven't got
> I/O coherency units). This also allow us to properly enable this driver to
> completely be enabled for COMPILE_TEST. This patchset appoarch:
> - Move windows list splice in 'pci_register_host_bridge()' after function
>   'pcibios_root_bridge_prepare()' is called.
> - Implement 'pcibios_root_bridge_prepare()' for ralink mt7621.
> - Avoid custom MIPs code in pcie-mt7621 driver.
> - Add missing 'MODULE_LICENSE()' to pcie-mt7621 driver to avoid compile test
>   module compilation to complain (already sent patch from Yanteng Si that
>   I have rewrite commit message and long description a bit.
> - Remove MIPS conditional code from Kconfig and mark driver as 'tristate'.
> 
> This patchset is a real fix for some errors reported by Kernel Test Robot about
> implicit mips functions used in driver code and fix errors in driver when
> is compiled as a module [1] (mips:allmodconfig).
> 
> Changes in v3:
>  - Rebase the series on the top of the temporal fix sent for v5.16[3] for
>    the module compilation problem.
>  - Address review comments from Guenter in PATCH 2 (thanks Guenter!):
>     - Address TODO in comment about the hardware does not allow zeros
>       after 1s for the mask and WARN_ON if that's happend.
>     - Be sure mask is real valid upper 16 bits.
> 
> Changes in v2:
>  - Collect Acked-by from Arnd Bergmann for PATCH 1.
>  - Collect Reviewed-by from Krzysztof Wilczyński for PATCH 4.
>  - Adjust some patches commit subject and message as pointed out by Bjorn in review of v1 of the series[2]. 
> 
> This patchset is the good way of properly compile driver as a module removing
> all MIPS specific code into arch ralink mt7621 place. To avoid mips:allmodconfig reported
> problems for v5.16 the following patch has been sent[3]. This series are rebased onto this patch to provide
> a real fix for this problem.
> 
> [0]: https://lore.kernel.org/linux-mips/CAMhs-H8ShoaYiFOOzJaGC68nZz=V365RXN_Kjuj=fPFENGJiiw@mail.gmail.com/T/#t
> [1]: https://lkml.org/lkml/2021/11/14/436
> [2]: https://lore.kernel.org/r/20211115070809.15529-1-sergio.paracuellos@gmail.com
> [3]: https://lore.kernel.org/linux-pci/20211203192454.32624-1-sergio.paracuellos@gmail.com/T/#u
> 
> Thanks in advance for your time.
> 
> Best regards,
>    Sergio Paracuellos
> 
> Sergio Paracuellos (5):
>   PCI: Let pcibios_root_bridge_prepare() access to 'bridge->windows'
>   MIPS: ralink: implement 'pcibios_root_bridge_prepare()'
>   PCI: mt7621: Avoid custom MIPS code in driver code
>   PCI: mt7621: Add missing 'MODULE_LICENSE()' definition
>   PCI: mt7621: Allow COMPILE_TEST for all arches
> 
>  arch/mips/ralink/mt7621.c            | 31 ++++++++++++++++++++++
>  drivers/pci/controller/Kconfig       |  4 +--
>  drivers/pci/controller/pcie-mt7621.c | 39 ++--------------------------
>  drivers/pci/probe.c                  |  4 +--
>  4 files changed, 37 insertions(+), 41 deletions(-)

I tentatively put this on my pci/host/mt7621 branch.  The only
non-mt7621 change is the pci_register_host_bridge() change, which
seems innocuous, so maybe we can still squeeze it in.

I squashed these patches together:

  MIPS: ralink: implement 'pcibios_root_bridge_prepare()'
  PCI: mt7621: Avoid custom MIPS code in driver code

because the first adds the coherency setup to the MIPS
pcibios_root_bridge_prepare(), and the second removes that same code
from pcie-mt7621.c.  I think it makes more sense to do it as a move in
a single patch, both for ease of reviewing and for potential
bisection.