Re: [PATCH 4/5] bus: mhi: host: Update the Time sync logic to read 64 bit register value

On 9/2/2025 2:44 PM, Konrad Dybcio wrote:
> On 8/18/25 8:55 AM, Krishna Chaitanya Chundru wrote:
>> Instead of reading low and high of the mhi registers twice use 64 bit
>> register value to avoid any time penality.
>>
>> Signed-off-by: Krishna Chaitanya Chundru <[email protected]>
>> ---
>>  drivers/bus/mhi/host/main.c | 19 +++++++++++++++----
>>  1 file changed, 15 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
>> index b7ceeb7261b708d46572d1f68dc277b6e1186b6e..f628198218ef9dc760bbfc3ec496603d1a45dfc1 100644
>> --- a/drivers/bus/mhi/host/main.c
>> +++ b/drivers/bus/mhi/host/main.c
>> @@ -1719,6 +1719,7 @@ static int mhi_get_remote_time(struct mhi_controller *mhi_cntrl, struct mhi_time
>>  			       struct mhi_timesync_info *time)
>>  {
>>  	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>> +	u64 val = U64_MAX;
>>  	int ret, i;
>>  
>>  	if (!mhi_tsync && !mhi_tsync->time_reg) {
>> @@ -1756,15 +1757,25 @@ static int mhi_get_remote_time(struct mhi_controller *mhi_cntrl, struct mhi_time
>>  	 * transition to L0.
>>  	 */
>>  	for (i = 0; i < MHI_NUM_BACK_TO_BACK_READS; i++) {
>> -		ret = mhi_read_reg(mhi_cntrl, mhi_tsync->time_reg,
>> -				   TSC_TIMESYNC_TIME_LOW_OFFSET, &time->t_dev_lo);
>> +		if (mhi_cntrl->read_reg64) {
>> +			ret = mhi_read_reg64(mhi_cntrl, mhi_tsync->time_reg,
>> +					     TSC_TIMESYNC_TIME_LOW_OFFSET, &val);
> Since you're passing mhi_cntrl to the read_reg64 function anyway,
> perhaps this could remove some verbosity:
Hi Konrad,

Sorry for late reply, in pci_generic patch we are defining read_reg64 only if
readq is defined
in the system.  As per your suggesting if we go define mhi_read_reg64 always,
we need to
have #ifdef inside the mhi_read_reg64() or create a new function  both of them
doesn't look
good better to have this way only.

- Krishna Chaitanya.
> int mhi_read_reg64(...) {
> 	u32 val_hi, val_lo;
> 	u64 val;
>
> 	if (mhi_cntrl->read_reg64) {
> 		...
> 	} else {
> 		...
> 		val = FIELD_PREP(GENMASK(63, 32), val_hi)) |
> 		      FIELD_PREP(GENMASK(31, 0), val_lo));
> 	}
>
> 	return val
> }
>
>
> Konrad