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

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Message-ID: <16698a59-1a2f-4816-98fe-56b125be669b@oss.qualcomm.com>
Date: Tue, 2 Sep 2025 11:14:46 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Richard Cochran <richardcochran@...il.com>
Cc: mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        taniya.das@....qualcomm.com, imran.shaik@....qualcomm.com,
        quic_vbadigan@...cinc.com, quic_mrana@...cinc.com
Subject: Re: [PATCH 4/5] bus: mhi: host: Update the Time sync logic to read 64
 bit register value

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 <krishna.chundru@....qualcomm.com>
> ---
>  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:

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