Quoting Lina Iyer (2019-07-23 12:21:59)
> On Tue, Jul 23 2019 at 12:22 -0600, Stephen Boyd wrote:
> >Quoting Lina Iyer (2019-07-22 14:53:37)
> >> From: "Raju P.L.S.S.S.N" <rplsssn@xxxxxxxxxxxxxx>
> >>
> >> The tcs->lock was introduced to serialize access with in TCS group. But,
> >> drv->lock is still needed to synchronize core aspects of the
> >> communication. This puts the drv->lock in the critical and high latency
> >> path of sending a request. drv->lock provides the all necessary
> >> synchronization. So remove locking around TCS group and simply use the
> >> drv->lock instead.
> >
> >This doesn't talk about removing the irq saving and restoring though.
> You mean for drv->lock? It was not an _irqsave/_irqrestore anyways and
> we were only removing the tcs->lock.
Yes drv->lock wasn't an irqsave/restore variant because it was a
spinlock inside of an obviously already irqsaved region of code because
the tcs->lock was outside the drv->lock and that was saving the irq
flags.
>
> >Can you keep irq saving and restoring in this patch and then remove that
> >in the next patch with reasoning? It probably isn't safe if the lock is
> >taken in interrupt context anyway.
> >
> Yes, the drv->lock should have been irqsave/irqrestore, but it hasn't
> been changed by this patch.
It needs to be changed to maintain the irqsaving/restoring of the code.
> >> @@ -349,41 +349,35 @@ static int tcs_write(struct rsc_drv *drv, const struct tcs_request *msg)
> >> {
> >> struct tcs_group *tcs;
> >> int tcs_id;
> >> - unsigned long flags;
> >> int ret;
> >>
> >> tcs = get_tcs_for_msg(drv, msg);
> >> if (IS_ERR(tcs))
> >> return PTR_ERR(tcs);
> >>
> >> - spin_lock_irqsave(&tcs->lock, flags);
> >> spin_lock(&drv->lock);
> >> /*
> >> * The h/w does not like if we send a request to the same address,
> >> * when one is already in-flight or being processed.
> >> */
> >> ret = check_for_req_inflight(drv, tcs, msg);
> >> - if (ret) {
> >> - spin_unlock(&drv->lock);
> >> + if (ret)
> >> goto done_write;
> >> - }
> >>
> >> tcs_id = find_free_tcs(tcs);
> >> if (tcs_id < 0) {
> >> ret = tcs_id;
> >> - spin_unlock(&drv->lock);
> >> goto done_write;
> >> }
> >>
> >> tcs->req[tcs_id - tcs->offset] = msg;
> >> set_bit(tcs_id, drv->tcs_in_use);
> >> - spin_unlock(&drv->lock);
> >>
> >> __tcs_buffer_write(drv, tcs_id, 0, msg);
> >> __tcs_trigger(drv, tcs_id);
> >>
> >> done_write:
> >> - spin_unlock_irqrestore(&tcs->lock, flags);
> >> + spin_unlock(&drv->lock);
> >> return ret;
> >> }
> >>
> >> @@ -481,19 +475,18 @@ static int tcs_ctrl_write(struct rsc_drv *drv, const struct tcs_request *msg)
> >> {
> >> struct tcs_group *tcs;
> >> int tcs_id = 0, cmd_id = 0;
> >> - unsigned long flags;
> >> int ret;
> >>
> >> tcs = get_tcs_for_msg(drv, msg);
> >> if (IS_ERR(tcs))
> >> return PTR_ERR(tcs);
> >>
> >> - spin_lock_irqsave(&tcs->lock, flags);
> >> + spin_lock(&drv->lock);
> >> /* find the TCS id and the command in the TCS to write to */
> >> ret = find_slots(tcs, msg, &tcs_id, &cmd_id);
> >> if (!ret)
> >> __tcs_buffer_write(drv, tcs_id, cmd_id, msg);
> >> - spin_unlock_irqrestore(&tcs->lock, flags);
> >> + spin_unlock(&drv->lock);
> >>
> >
> >These ones, just leave them doing the irq save restore for now?
> >
> drv->lock ??
>
Yes, it should have irq save/restore still.
