Re: [RFC PATCH 0/8] cxl: Introduce HDM decoder emulation from DVSEC range registers

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

On Wed, 30 Nov 2022 16:12:15 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

> This series provides the emulation of HDM decoders from the programmed range
> registers. From CXL 3.0 spec 8.1.3.8, there can be up to 2 ranges programmed.
> Some device may not implement HDM decoder registers and some may not be
> programmed by the BIOS. Under such scenarios, if one of more range registers
> are programmed, then we can create an emulated HDM decoder per active range
> indicated by the range registers. The emulated HDM decoders will show up as
> locked and cannot be reprogrammed.
> 
> Below is a table that indicates different scenarios the driver may encounter:
> 
> rr: Range registers not programmed
> hdm: HDM decoders not programmed
> RR: Range registers programmed by BIOS
> HDM: HDM decoders programmed by BIOS
> 
> emulate HDM: Create HDM decoder software structs and use values from range registers.
> keep HDM: Populate HDM decoder software structs with values in HDM decoder registers.
> 
> rr             RR             rr hdm	 rr HDM	     RR hdm        RR HDM
> unsupported    emulate HDM    keep HDM	 keep HDM    emulate HDM   keep HDM
> 
> This series is based on the current RCD work [1] that's going through upstream review.
> For convenience, the kernel branch can be retrieved here [2].

Just to check, why is this an RFC rather than a normal submission?
Because of the unstable dependency?

At least at top level, it looks like a sensible approach.

> 
> [1]: https://lore.kernel.org/linux-cxl/Y4ePZD776yXv2rG3@rric.localdomain/T/#t
> [2]: https://git.kernel.org/pub/scm/linux/kernel/git/djiang/linux.git/log/?h=cxl-rch
> 
> ---
> 
> Dave Jiang (8):
>       cxl: break out range register decoding from cxl_hdm_decode_init()
>       cxl: export cxl_dvsec_rr_decode() to cxl_port
>       cxl: refactor cxl_hdm_decode_init()
>       cxl: emulate HDM decoder from DVSEC range registers
>       cxl: create emulated cxl_hdm for devices that do not have HDM decoders
>       cxl: create emulated decoders for devices without HDM decoders
>       cxl: suppress component register discovery failure warning for RCD
>       cxl: remove locked check for dvsec_range_allowed()
> 
> 
>  drivers/cxl/core/hdm.c | 115 +++++++++++++++++++++++---
>  drivers/cxl/core/pci.c | 179 +++++++++++++++++------------------------
>  drivers/cxl/cxl.h      |  20 ++++-
>  drivers/cxl/cxlmem.h   |  13 +--
>  drivers/cxl/cxlpci.h   |   3 +-
>  drivers/cxl/pci.c      |   2 +-
>  drivers/cxl/port.c     |  19 +++--
>  7 files changed, 215 insertions(+), 136 deletions(-)
> 
> --
>