Re: [RFC PATCH] interconnect: qcom: icc-rpm: Don't call __qcom_icc_set twice on the same node

[Bryan O'Donoghue <bryan.odonoghue@linaro.org>]

On 03/03/2023 11:39, Konrad Dybcio wrote:
> 
> 
> On 3.03.2023 12:36, Bryan O'Donoghue wrote:
>> On 03/03/2023 11:35, Bryan O'Donoghue wrote:
>>> On 03/03/2023 11:33, Konrad Dybcio wrote:
>>>>
>>>>
>>>> On 3.03.2023 12:32, Bryan O'Donoghue wrote:
>>>>> On 03/03/2023 02:35, Konrad Dybcio wrote:
>>>>>> Currently, when sync_state calls set(n, n) all the paths for setting
>>>>>> parameters on an icc node are called twice. Avoid that.
>>>>>>
>>>>>> Fixes: 751f4d14cdb4 ("interconnect: icc-rpm: Set destination bandwidth as well as source bandwidth")
>>>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
>>>>>> ---
>>>>>> RFC comes from the fact that I *believe* this should be correct, but I'm
>>>>>> not entirely sure about it..
>>>>>>
>>>>>>
>>>>>>     drivers/interconnect/qcom/icc-rpm.c | 2 +-
>>>>>>     1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/interconnect/qcom/icc-rpm.c b/drivers/interconnect/qcom/icc-rpm.c
>>>>>> index a6e0de03f46b..d35db1af9b08 100644
>>>>>> --- a/drivers/interconnect/qcom/icc-rpm.c
>>>>>> +++ b/drivers/interconnect/qcom/icc-rpm.c
>>>>>> @@ -387,7 +387,7 @@ static int qcom_icc_set(struct icc_node *src, struct icc_node *dst)
>>>>>>         ret = __qcom_icc_set(src, src_qn, sum_bw);
>>>>>>         if (ret)
>>>>>>             return ret;
>>>>>> -    if (dst_qn) {
>>>>>> +    if (dst_qn && src_qn != dst_qn) {
>>>>>>             ret = __qcom_icc_set(dst, dst_qn, sum_bw);
>>>>>>             if (ret)
>>>>>>                 return ret;
>>>>>
>>>>> Is it possible for src_qn == dst_qn ?
>>>> As the commit message says, sync_state calls set(n, n) in
>>>> drivers/interconnect/core.c : icc_sync_state(struct device *dev)
>>>
>>> So you've _seen_ that happen ?
>>>
>>
>> Assuming you have, then why isn't the fix in sync_state i.e. that's an error for everybody right ?
> I believe that there's simply no other way of updating every single node
> on its own with the icc api, without taking any links into play. But I
> see exynos and i.mx also effectively calling it twice on each node.
> 
> Konrad

I mean. I'm fine for you to retain my RB on this qcom specific patch 
since this seems like a real bug to me but... it seems like a generic 
bug across arches that should probably be resolved @ the higher level.

?

---
bod