Re: [RFC 02/13] cxl: introduce cxl_get_hdm_info()

[Zhi Wang <zhiw@nvidia.com>]

On 17/10/2024 18.44, Jonathan Cameron wrote:
> External email: Use caution opening links or attachments
> 
> 
> On Fri, 20 Sep 2024 15:34:35 -0700
> Zhi Wang <zhiw@nvidia.com> wrote:
> 
>> CXL core has the information of what CXL register groups a device has.
>> When initializing the device, the CXL core probes the register groups
>> and saves the information. The probing sequence is quite complicated.
>>
>> vfio-cxl requires the HDM register information to emualte the HDM decoder
> Hi Zhi,
> 
> I know these were a bit rushed out so I'll only comment once.
> Give your patch descriptions a spell check (I always forget :)
> emulate
> 

Thanks for pointing it out. Will proceed. Lol. Me the same. I write a 
script of sending patches that ask for confirming every item was in the 
checklist now.

>> registers.
>>
>> Introduce cxl_get_hdm_info() for vfio-cxl to leverage the HDM
>> register information in the CXL core. Thus, it doesn't need to implement
>> its own probing sequence.
>>
>> Signed-off-by: Zhi Wang <zhiw@nvidia.com>
>> ---
>>   drivers/cxl/core/pci.c        | 28 ++++++++++++++++++++++++++++
>>   drivers/cxl/cxlpci.h          |  3 +++
>>   include/linux/cxl_accel_mem.h |  2 ++
>>   3 files changed, 33 insertions(+)
>>
>> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
>> index a663e7566c48..7b6c2b6211b3 100644
>> --- a/drivers/cxl/core/pci.c
>> +++ b/drivers/cxl/core/pci.c
>> @@ -502,6 +502,34 @@ int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
>>   }
>>   EXPORT_SYMBOL_NS_GPL(cxl_hdm_decode_init, CXL);
>>
>> +int cxl_get_hdm_info(struct cxl_dev_state *cxlds, u32 *hdm_count,
>> +                  u64 *hdm_reg_offset, u64 *hdm_reg_size)
>> +{
>> +     struct pci_dev *pdev = to_pci_dev(cxlds->dev);
>> +     int d = cxlds->cxl_dvsec;
>> +     u16 cap;
>> +     int rc;
>> +
>> +     if (!cxlds->reg_map.component_map.hdm_decoder.valid) {
>> +             *hdm_reg_offset = *hdm_reg_size = 0;
> Probably want to zero out the hdm_count as well?
> 
>> +     } else {
>> +             struct cxl_component_reg_map *map =
>> +                     &cxlds->reg_map.component_map;
>> +
>> +             *hdm_reg_offset = map->hdm_decoder.offset;
>> +             *hdm_reg_size = map->hdm_decoder.size;
>> +     }
>> +
>> +     rc = pci_read_config_word(pdev,
>> +                               d + CXL_DVSEC_CAP_OFFSET, &cap);
>> +     if (rc)
>> +             return rc;
>> +
>> +     *hdm_count = FIELD_GET(CXL_DVSEC_HDM_COUNT_MASK, cap);
>> +     return 0;
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_get_hdm_info, CXL);