On Wed, Feb 22, 2023 at 11:07:48PM +0530, Vivek Pernamitta wrote: > 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. This could cause > doorbell event to be processed by MHI device to check for > any ring elements even it is none and also it will occupy > lot of bandwidth on peripheral when mhi_poll() is called in > aggressive loop. > The change looks good to me but who is the actual in-kernel user of mhi_poll() API? It is being exported and if there is no upstream client driver making use of it, then it shouldn't be. I'm gonna submit a patch to remove this API altogether. > Signed-off-by: Vivek Pernamitta <quic_vpernami@xxxxxxxxxxx> > Reviewed-by: Jeffrey Hugo <quic_jhugo@xxxxxxxxxxx> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> Thanks, Mani > > --- > changes since v4: > updating the commit text with more information. > 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); > > -- > 2.7.4 >
