Re: [PATCH 0/7] soc: aspeed: Add AST2600 eSPI controller support

[Andrew Jeffery <andrew@codeconstruct.com.au>]

On Fri, 2026-03-13 at 22:36 +0100, Arnd Bergmann wrote:
> On Fri, Mar 13, 2026, at 17:24, Conor Dooley wrote:
> > On Fri, Mar 13, 2026 at 06:07:35PM +0800, aspeedyh wrote:
> > > This series adds initial support for the eSPI controller found on ASPEED
> > > AST2600 BMC SoCs.
> > > 
> > > The series introduces a eSPI controller framework for ASPEED SoCs under
> > > drivers/soc/aspeed/, adds AST2600-specific controller support for
> > > peripheral and flash channels, defines the corresponding devicetree 
> > > binding, and adds the AST2600 eSPI controller node to the SoC dtsi.
> > > 
> > > The driver is intended to support host-BMC communication over the BMC-side
> > > eSPI slave controller present on AST2600 systems.
> > 
> > This all seems to be in the wrong places entirely, shouldn't an eSPI
> > driver and bindings go in the spi subsystem?
> 
> From an initial reading, my impression is that patches 1, 2, 3 and 7
> should be modified to use the normal SPI interfaces to implement
> an spi target driver, possibly a combined host/target driver.
> Reworking this should be fairly straightforward because the interfaces
> to the SPI core are well documented.
> 
> It is possible that the hardware can only be used to provide espi
> device emulation. From what I could see in the code, there is
> not much special in there, but I'm not that familiar with SPI
> 
> Patches 4, 5 and 6 in consequently would need to be reworked so
> these can implement the TAFS spec independent of the SPI controller,
> and can be shared e.g. with other OpenBMC targets using the same
> module and the same user interface. None of this should be aspeed
> specific. 
> 
> There is a good chance that both the user interface and the placing
> of the code will need a more debate, but I would suggest first trying
> to move everything over to use the SPI subsystem but leave other
> parts untouched for the moment.

To extend Arnd's points here, some previous attempts were made to
support Intel's eSPI protocol on Aspeed's SoCs which aren't discussed
in this cover letter. I think it would be helpful to cover the history
and why we now have a third approach:

- https://lore.kernel.org/linux-aspeed/20240319093405.39833-1-manojkiran.eda@gmail.com/
- https://lore.kernel.org/openbmc/20220516005412.4844-1-chiawei_wang@aspeedtech.com/

Previously, Jeremy had some suggestions covering the various channels:

https://lore.kernel.org/linux-aspeed/20c13b9bb023091758cac3a07fb4037b7d796578.camel@codeconstruct.com.au/

Andrew