Re: [PATCH v2 04/15] arm_mpam: propagate MSC read errors for mpam_msc_read_mbwu_l()

[Andre Przywara <andre.przywara@arm.com>]

Hi Ben,

On 7/1/26 22:06, Ben Horgan wrote:
> Hi Andre,
> 
> On 7/2/26 17:22, Andre Przywara wrote:
>> Allow the mpam_msc_read_mbwu_l() function to return an error, and
>> propagate read errors from the lower level up.
>>
>> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
>> ---
>>   drivers/resctrl/mpam_devices.c | 13 ++++++++++---
>>   1 file changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
>> index 011d1e3544d7..1d06902fb970 100644
>> --- a/drivers/resctrl/mpam_devices.c
>> +++ b/drivers/resctrl/mpam_devices.c
>> @@ -1106,6 +1106,7 @@ static bool mpam_ris_has_mbwu_long_counter(struct mpam_msc_ris *ris)
>>   
>>   static u64 mpam_msc_read_mbwu_l(struct mpam_msc *msc)
> 
> Now that your changing the other helpers to return an error and pass a
> pointer to hold the register value it would seem more consistent for
> this call to follow the same pattern.

Ah, I wasn't entirely sure whether this MSMON___L_NRDY is just some 
error flag (abuse), since NRDY is some kind of architecture feature.
If that's indeed here the case, I will be changing the prototype and 
adjust the function.

Cheers,
Andre

> Thanks,
> 
> Ben
> 
>>   {
>> +	int ret;
>>   	int retry = 3;
>>   	u32 mbwu_l_low;
>>   	u32 mbwu_l_high1, mbwu_l_high2;
>> @@ -1115,11 +1116,17 @@ static u64 mpam_msc_read_mbwu_l(struct mpam_msc *msc)
>>   	WARN_ON_ONCE((MSMON_MBWU_L + sizeof(u64)) > msc->mapped_hwpage_sz);
>>   	WARN_ON_ONCE(!cpumask_test_cpu(smp_processor_id(), &msc->accessibility));
>>   
>> -	__mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2);
>> +	ret = __mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2);
>> +	if (ret)
>> +		return MSMON___L_NRDY;
>> +
>>   	do {
>>   		mbwu_l_high1 = mbwu_l_high2;
>> -		__mpam_read_reg(msc, MSMON_MBWU_L, &mbwu_l_low);
>> -		__mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2);
>> +		ret = __mpam_read_reg(msc, MSMON_MBWU_L, &mbwu_l_low);
>> +		if (!ret)
>> +			ret = __mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2);
>> +		if (ret)
>> +			return MSMON___L_NRDY;
>>   
>>   		retry--;
>>   	} while (mbwu_l_high1 != mbwu_l_high2 && retry > 0);
>