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SubjectRe: [PATCH v4] bus: mhi: host: Avoid ringing EV DB if there is no elements to process
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On 2/22/2023 4:43 AM, Vivek Pernamitta wrote:
> Avoid ringing Event DB if there is no elements to process.

This is almost exactly identical to $SUBJECT and therefore redundant.

> As mhi_poll function can be called by mhi client drivers
> which will call process_event, which will ring DB even if
> there no ring elements to process.

I think that you could be more clear on why this is a problem that
should be addressed. Perhaps add a sentence like "These doorbell events
needlessly interrupt the MHI device to checked for ring elements when
there are none."

With the commit text updated, you can add
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>

>
> Signed-off-by: Vivek Pernamitta <quic_vpernami@quicinc.com>
>
> ---
> changes since v3:
> - Updating commit text for multiple versions of patches.
> changes since v2:
> - Updated comments in code.
> changes since v1:
> - Add an check to avoid ringing EV DB in mhi_process_ctrl_ev_ring().
> ---
> drivers/bus/mhi/host/main.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
> index df0fbfe..1bbdb75 100644
> --- a/drivers/bus/mhi/host/main.c
> +++ b/drivers/bus/mhi/host/main.c
> @@ -961,7 +961,9 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
> }
>
> read_lock_bh(&mhi_cntrl->pm_lock);
> - if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)))
> +
> + /* Ring EV DB only if there is any pending element to process */
> + if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)) && count)
> mhi_ring_er_db(mhi_event);
> read_unlock_bh(&mhi_cntrl->pm_lock);
>
> @@ -1031,7 +1033,9 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
> count++;
> }
> read_lock_bh(&mhi_cntrl->pm_lock);
> - if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)))
> +
> + /* Ring EV DB only if there is any pending element to process */
> + if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)) && count)
> mhi_ring_er_db(mhi_event);
> read_unlock_bh(&mhi_cntrl->pm_lock);
>

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