On 16.04.2016 16:36, Jayachandran C wrote:
On Sat, Apr 16, 2016 at 1:01 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
On Saturday 16 April 2016 12:50:13 Jayachandran C wrote:
I still think it would be better to keep the loadable PCI host drivers
separate from the ACPI PCI infrastructure. There are a number of
simplifications that we want to do to the DT based drivers in the long
run, so it's better if that code is not shared at this level. Abstracting
out the ECAM code is fine, but at that point you should be able to just
call it from the ACPI layer.
The issue is not with this patch (in my opinion). This patch is just
re-arranging how thunder specific data is maintained. Earlier it was
a container_of gen_pci, now it is ->priv of pci_config_window.
I can see the issue in patches 12 and 13 of this patchset which adds
ACPI fixups into the thunder OF driver.
Right, I commented on this one, because it seems to rearrange the code
in order to do the later one.
Patches 11- 13 are not from me, and I am not completely on board
on the approach of adding the sections.We can look at reworking this.
The simple approach when doing modular PCI drivers would be to make
pci-thunder-*.c like pci-host-common.c, to be compiled in if configured.
The fie will contain all the Thunder quirks and can export
pci_thunder_ecam_ops.
I would argue that we should not export anything from drivers/pci/host,
those should really be standalone drivers that do not interact with other
subsystems.
pci-host-common.c goes against being standalone. The files calling
pci_host_common_probe() are expected to have custom ECAM ops
the way it is written now. We need to have a reasonable way to share
those ECAM ops if needed by ACPI.
How much code would you need to duplicate from thunder-ecam to have
the same functionality available in ACPI? My expectation is that it's
not really that much more compared to the code you need for sharing
a single implementation, but you get a lower complexity here, which
makes it easier to understand and to rework.
Like I wrote above, the sharing is really simple because both generic
ACPI and pci-host-common.c have been written for "ECAM with quirks".
The whole pci-thunder-*.c is to support thunder PCI quirks since the
generic OF is handled by pci-host-common.c and generic ECAM is now
separated - duplicating the whole file for ACPI will be bad.
Yes, it would be too much code duplication. Also, we already know
drivers which need quirks.
We really need to agree on best approach here. Here are requirements
which came up (please correct me if misunderstood sth):
Arnd:
1. Initial DT driver should be standalone [Arnd]
2. No exported symbols [Arnd]
3. Duplicate necessary code to ACPI framework.
JC:
1. Adding linker section is wrong.
2. Quirks should be exported (pci_thunder_ecam_ops), then no need for
adding linker section
3. To much duplication to copy code into the ACPI framework.
My opinion:
1. I like linker section because it is easy to maintain and no need to
export symbols.
2. We need more sophisticated algorithm for matching quirks (DMI is not
enough and not only for ThunderX drivers). Of course I am open to any
new suggestions.
3. To much duplication to copy code into the ACPI framework.
Thanks in advance for any pointers.
Thanks,
Tomasz
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