Re: [PATCH v2 1/1] cxl/hdm: Add support for 32 switch decoders

[Dave Jiang]

On 4/10/26 1:17 AM, Li Ming wrote:
> kindly ping.
> 
> Is this patch missing in cxl/next?

Sorry I missed it. Applied to cxl/next
3624a22783b7


> 
> 
> Ming
> 
> 在 2026/3/21 14:14, Li Ming 写道:
>> Per CXL r4.0 section 8.2.4.20.1. CXL host bridge and switch ports can
>> support 32 HDM decoders. Current implementation misses some decoders on
>> CXL host bridge and switch in the case that the value of Decoder Count
>> field in CXL HDM decoder Capability Register is greater than or equal to
>> 9.
>>
>> Update calculation implementation to ensure the decoder count calculation
>> is correct for CXL host bridge/switch ports.
>>
>> Signed-off-by: Li Ming <ming.li@xxxxxxxxxxxx>
>> ---
>> Changes from v1:
>> - Return -ENXIO if the value violates SPEC. (Dave & Alison)
>> ---
>>   drivers/cxl/core/hdm.c |  2 +-
>>   drivers/cxl/cxl.h      | 11 ++++++++++-
>>   drivers/cxl/cxlmem.h   |  2 +-
>>   3 files changed, 12 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
>> index c222e98ae736..3930e130d6b6 100644
>> --- a/drivers/cxl/core/hdm.c
>> +++ b/drivers/cxl/core/hdm.c
>> @@ -177,7 +177,7 @@ static struct cxl_hdm *devm_cxl_setup_hdm(struct cxl_port *port,
>>       }
>>         parse_hdm_decoder_caps(cxlhdm);
>> -    if (cxlhdm->decoder_count == 0) {
>> +    if (cxlhdm->decoder_count < 0) {
>>           dev_err(dev, "Spec violation. Caps invalid\n");
>>           return ERR_PTR(-ENXIO);
>>       }
>> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
>> index 9b947286eb9b..0a5301049cf3 100644
>> --- a/drivers/cxl/cxl.h
>> +++ b/drivers/cxl/cxl.h
>> @@ -77,7 +77,16 @@ static inline int cxl_hdm_decoder_count(u32 cap_hdr)
>>   {
>>       int val = FIELD_GET(CXL_HDM_DECODER_COUNT_MASK, cap_hdr);
>>   -    return val ? val * 2 : 1;
>> +    switch (val) {
>> +    case 0:
>> +        return 1;
>> +    case 1 ... 8:
>> +        return val * 2;
>> +    case 9 ... 12:
>> +        return (val - 4) * 4;
>> +    default:
>> +        return -ENXIO;
>> +    }
>>   }
>>     /* Encode defined in CXL 2.0 8.2.5.12.7 HDM Decoder Control Register */
>> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
>> index e21d744d639b..399b150b404c 100644
>> --- a/drivers/cxl/cxlmem.h
>> +++ b/drivers/cxl/cxlmem.h
>> @@ -923,7 +923,7 @@ int cxl_mem_sanitize(struct cxl_memdev *cxlmd, u16 cmd);
>>    */
>>   struct cxl_hdm {
>>       struct cxl_component_regs regs;
>> -    unsigned int decoder_count;
>> +    int decoder_count;
>>       unsigned int target_count;
>>       unsigned int interleave_mask;
>>       unsigned long iw_cap_mask;