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SubjectRe: [PATCH v2 2/2] ACPI/PPTT: Handle architecturally unknown cache types
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On 9/17/2018 10:17 AM, Sudeep Holla wrote:
>
>
> On 14/09/18 17:28, Jeffrey Hugo wrote:
>> The type of a cache might not be specified by architectural mechanisms (ie
>> system registers), but its type might be specified in the PPTT. In this
>> case, we should populate the type of the cache, rather than leave it
>> undefined.
>>
>> This fixes the issue where the cacheinfo driver will not populate sysfs
>> for such caches, resulting in the information missing from utilities like
>> lstopo and lscpu, thus degrading the user experience.
>>
>> Fixes: 2bd00bcd73e5 (ACPI/PPTT: Add Processor Properties Topology Table parsing)
>> Reported-by: Vijaya Kumar K <vkilari@codeaurora.org>
>> Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>
>> ---
>> drivers/acpi/pptt.c | 15 +++++++++++----
>> 1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
>> index d1e26cb..bb00ed9 100644
>> --- a/drivers/acpi/pptt.c
>> +++ b/drivers/acpi/pptt.c
>> @@ -402,11 +402,18 @@ static void update_cache_properties(struct cacheinfo *this_leaf,
>> }
>> }
>> /*
>> - * If the above flags are valid, and the cache type is NOCACHE
>> - * update the cache type as well.
>> + * If cache type is NOCACHE, then the cache hasn't been specified
>> + * via other mechanisms. Update the type if either the cache has
>> + * been fully specified in PPTT, or a cache type has been provided.
>> + *
>> + * Note, we assume such caches are unified based on conventional system
>> + * design and known examples. Significant work is required elsewhere to
>> + * fully support data/instruction only type caches which are only
>> + * specified in PPTT.
>> */
>> - if (this_leaf->type == CACHE_TYPE_NOCACHE &&
>> - valid_flags == PPTT_CHECKED_ATTRIBUTES)
>> + if ((this_leaf->type == CACHE_TYPE_NOCACHE) &&
>> + (valid_flags == PPTT_CHECKED_ATTRIBUTES ||
>> + found_cache->flags & ACPI_PPTT_CACHE_TYPE_VALID))
>> this_leaf->type = CACHE_TYPE_UNIFIED;
>
> I thought I did mention that we can drop the valid_flags altogether
> unless Jeremy has reasons not to.
>

You suggested that perhaps that could be the case. It seemed like an
open question to me. I'm at Linaro Connect without access to the device
this week, so I guess someone has roughly a week to chime in that the
valid flags should be kept, otherwise I'll try a v3 with them removed.

--
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

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