[3/3] phy: marvell: phy-mvebu-a3700-comphy: Remove unsupported modes

Armada 3700 does not support RXAUI, XFI and neither SFI. Remove unused
macros for these unsupported modes.

Signed-off-by: Pali Rohár <pali@kernel.org>
Fixes: 9695375a3f4a ("phy: add A3700 COMPHY support")
---
 drivers/phy/marvell/phy-mvebu-a3700-comphy.c | 6 ------
 1 file changed, 6 deletions(-)

On Fri, 27 Aug 2021 11:27:53 +0200
Pali Rohár <pali@kernel.org> wrote:

> Armada 3700 does not support RXAUI, XFI and neither SFI. Remove unused
> macros for these unsupported modes.
> 
> Signed-off-by: Pali Rohár <pali@kernel.org>
> Fixes: 9695375a3f4a ("phy: add A3700 COMPHY support")

BTW I was thinking about merging some parts of these 2 drivers into
common code. Not entirely sure if I should follow, though.

On Fri, Aug 27, 2021 at 08:25:02PM +0200, Pali Rohár wrote:
> cp110-comphy and a3700-comphy are just RPC drivers which calls SMC and
> relay on firmware support which implements real work. And both uses same
> RPC / SMC API. So merging drivers into one is possible.
> 
> But I do not think that it is a good idea that Linux kernel depends on
> some external firmware which implements RPC API for configuring HW.
> 
> Rather kernel should implements its native drivers without dependency on
> external firmware.
> 
> We know from history that kernel tried to avoid using x86 BIOS/firmware
> due to bugs and all functionality (re)-implemented itself without using
> firmware RPC functionality.

Not really an argument in this case. We're not talking about closed
source firmware.

> Kernel has already "hacks" in other drivers which are using these comphy
> drivers, just because older versions of firmware do not support all
> necessary functionality and upgrading this firmware is not easy step
> (and sometimes even not possible; e.g. when is cryptographically
> signed).

The kernel used to (and probably still does) contain code to configure
the comphys. Having worked on trying to get the 10G lanes stable on
Macchiatobin, I much prefer the existing solution where it's in the
ATF firmware. I've rebuilt the firmware several times during the course
of that.

The advantage is that fixing the setup of the COMPHY is done in one
place, and it fixes it not only for the kernel, but also for u-boot
and UEFI too. So rather than having to maintain three different
places for a particular board, we can maintain the parameters in one
place - in the ATF firmware.

The problem with the past has been that stuff gets accepted into the
kernel without the "full system" view and without regard for "should
this actually be done in the firmware". Then, when it's decided that
it really should be done in the firmware, we end up needing to keep
the old stuff in the kernel for compatibility with older firmware,
which incidentally may not be up to date.

If we were to drop the comphy setup from firmware, then we will need
a lot of additional properties in the kernel's DT and u-boot DT for
the comphy to configure it appropriately. And ACPI. I don't think
that scales very well, and is a recipe for things getting out of
step.

On Fri, Aug 27, 2021 at 09:02:34PM +0200, Pali Rohár wrote:
> I think that whatever is used (firmware code, kernel code, ...), DT
> should always contains full HW description with all nodes, and not only
> some "subset". DT should be independent of current driver / firmware
> implementation.

A "full" description of the hardware settings for the comphy on Armada
8040 would be very big if we included every single setting. There are
about a thousand settings - and that is likely an under-estimate. I
know, I've a shell script that decodes around a thousand settings from
the registers for a _single_ lane, and that's incomplete.

With many of the settings not very well documented in the manual, we
would struggle to describe it sufficiently well to get it past the DT
maintainers.

So, "full hardware description" is impractical. Sorry.