On Mon, May 11, 2020 at 07:03:09PM -0700, Hemant Kumar wrote:
> Take write lock only to protect db_mode member of mhi channel.
> This allows rest of the mhi channels to just take read lock which
> fine grains the locking. It prevents channel readers to starve if
> they try to enter critical section after a writer.
>
> Signed-off-by: Hemant Kumar <hemantk@xxxxxxxxxxxxxx>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
Thanks,
Mani
> ---
> drivers/bus/mhi/core/pm.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
> index 345f197..de5abb2 100644
> --- a/drivers/bus/mhi/core/pm.c
> +++ b/drivers/bus/mhi/core/pm.c
> @@ -288,14 +288,18 @@ int mhi_pm_m0_transition(struct mhi_controller *mhi_cntrl)
> for (i = 0; i < mhi_cntrl->max_chan; i++, mhi_chan++) {
> struct mhi_ring *tre_ring = &mhi_chan->tre_ring;
>
> - write_lock_irq(&mhi_chan->lock);
> - if (mhi_chan->db_cfg.reset_req)
> + if (mhi_chan->db_cfg.reset_req) {
> + write_lock_irq(&mhi_chan->lock);
> mhi_chan->db_cfg.db_mode = true;
> + write_unlock_irq(&mhi_chan->lock);
> + }
> +
> + read_lock_irq(&mhi_chan->lock);
>
> /* Only ring DB if ring is not empty */
> if (tre_ring->base && tre_ring->wp != tre_ring->rp)
> mhi_ring_chan_db(mhi_cntrl, mhi_chan);
> - write_unlock_irq(&mhi_chan->lock);
> + read_unlock_irq(&mhi_chan->lock);
> }
>
> mhi_cntrl->wake_put(mhi_cntrl, false);
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
