Re: [RFC PATCH 0/6] i2c: Enabling use of aspeed-i2c with ACPI

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Thu, 25 May 2023 16:21:57 +0100
Jonathan Cameron <Jonathan.Cameron@huawei.com> wrote:

> From the school of dirty hacks we do to prove something works, enable
> work to proceed elsewhere:
> 
> MCTP over I2C from ACPI emulated hosts (both x86 and ARM64).
> 
> The first 4 patches might be suitable for upstream inclusion, the
> last two not - though I hope we can move to Niyas' work on ACPI clock
> management once that is ready.
> 
> Why do this crazy thing?
> 
> Ultimately we want a standards based way to use the CXL Fabric Management
> API FM-API. In real systems that is likely to be driven from a separate
> 'host' such as a BMC, but for test purposes it is convenient to be able
> to do that from an QEMU emulated machine that is also capable of using
> the CXL kernel stack.
> 
> That CXL kernel stack is currently ACPI only (and people care about
> x86 for some reason). One of the defined interfaces over which FM-API
> commands can be issued is MCTP.
> 
> The kernel MCTP stack has upstream drivers for MCTP over I2C.
> Upstream QEMU emulates the Aspeed I2C controller with the necessary
> two way support. There are patches on list adding the MCTP parts
> https://lore.kernel.org/qemu-devel/20230425063540.46143-2-its@irrelevant.dk/
> and I've ported an earlier CXL FMAPI EP emulator over to that.
> 
> ACPI has a 'magic' HID of PRP0001 which allows the use of a device tree binding
> (mostly) with an ACPI DSDT entry.  A suitable chunk is something like
> 
> (dumped from a working x86 setup)
> 
>     Device (MCTP)
>     {
>         Name (_HID, "PRP0001")  // _HID: Hardware ID
>         Name (_DSD, Package (0x02)  // _DSD: Device-Specific Data
>         {
>             ToUUID ("daffd814-6eba-4d8c-8a91-bc9bbf4aa301") /* Device Properties for _DSD */,
>             Package (0x03)
>             {
>                 Package (0x02)
>                 {
>                      "compatible",
>                      "aspeed,ast2600-i2c-bus"
>                 },
>                 Package (0x02)
>                 {
>                     "bus-frequency",
>                     0x00061A80
>                 },
>                 Package (0x02)
>                 {
>                     "mctp-controller",
>                     One
>                 }
>             }
>         })
>         Name (_CRS, ResourceTemplate ()  // _CRS: Current Resource Settings
>         {
>             QWordMemory (ResourceProducer, PosDecode, MinFixed, MaxFixed, NonCacheable, ReadWrite,
>                 0x0000000000000000, // Granularity
>                 0x00000004800FC080, // Range Minimum
>                 0x00000004800FC0FF, // Range Maximum
>                 0x0000000000000000, // Translation Offset
>                 0x0000000000000080, // Length
>                 ,, , AddressRangeMemory, TypeStatic)
>             Interrupt (ResourceConsumer, Level, ActiveHigh, Shared, ,, )
>             {
>                 0x00000007,
>             }
>         })
>     }
>     Device (MCTS)
>     {
>         Name (_HID, "PRP0001")  // _HID: Hardware ID
>         Name (_CRS, ResourceTemplate ()  // _CRS: Current Resource Settings
>         {
>             I2cSerialBusV2 (0x0050, DeviceInitiated, 0x000186A0,
>                 AddressingMode7Bit, "\\_SB.MCTP",
>                 0x00, ResourceProducer, , Exclusive,
>                 )
>         })
>         Name (_DSD, Package (0x02)  // _DSD: Device-Specific Data
>         {
>             ToUUID ("daffd814-6eba-4d8c-8a91-bc9bbf4aa301") /* Device Properties for _DSD */,
>             Package (0x01)
>             {
>                 Package (0x02)
>                 {
>                     "compatible",
>                     "mctp-i2c-controller"
>                 }
>             }
>         })
>     }
> 
> QEMU patches will follow soon and will include documentation on
> how to actually poke this to do something useful. I'll post a reply
> to this with the link when posted.

https://lore.kernel.org/linux-cxl/20230525160859.32517-1-Jonathan.Cameron@huawei.com/T/#t
https://gitlab.com/jic23/qemu cxl-2023-05-25

> 
> Cc: Niyas Sait <niyas.sait@linaro.org>
> Cc: Klaus Jensen <its@irrelevant.dk>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Jeremy Kerr <jk@codeconstruct.com.au>
> Cc: Matt Johnston <matt@codeconstruct.com.au>
> Cc: Shesha Bhushan Sreenivasamurthy <sheshas@marvell.com>
> 
> Jonathan Cameron (6):
>   i2c: acpi: set slave mode flag
>   i2c: aspeed: Use platform_get_irq() instead of opencoding
>   i2c: aspeed: switch to generic fw properties.
>   i2c: aspeed: Set the fwnode for the adap->dev
>   HACK: i2c: aspeed: Comment the clock and reset out.
>   HACK: i2c: aspeed: Enable build without COMPILE_TEST
> 
>  drivers/i2c/busses/Kconfig      |  1 -
>  drivers/i2c/busses/i2c-aspeed.c | 36 ++++++++++++++++-----------------
>  drivers/i2c/i2c-core-acpi.c     |  3 +++
>  3 files changed, 20 insertions(+), 20 deletions(-)
> 
> 
> base-commit: f1fcbaa18b28dec10281551dfe6ed3a3ed80e3d6