| Message ID | 1677087470-7004-1-git-send-email-quic_vpernami@quicinc.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v5] bus: mhi: host: Avoid ringing EV DB if there is no elements to process | expand |
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@quicinc.com> > Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> 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 >
On Thu, Feb 23, 2023 at 09:18:36PM +0530, Manivannan Sadhasivam wrote: > 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. > The patch removing mhi_poll() API is now merged. Can you please respin this patch removing the note to the API? I still think this patch is relevant without that API. Thanks, Mani > > Signed-off-by: Vivek Pernamitta <quic_vpernami@quicinc.com> > > Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com> > > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> > > 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 > > >
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);