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

[Dave Jiang <dave.jiang@intel.com>]

On 12/19/22 09:12, Jonathan Cameron wrote:
> 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?

That and also just making sure people are ok with the direction of the 
series. I can remove the RFC for the next rev.

> 
> 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(-)
>>
>> --
>>
>