Re: [PATCH v5 05/10] drivers: qcom: rpmh-rsc: write sleep/wake requests to TCS

[Lina Iyer]

On Tue, Apr 10 2018 at 18:31 -0600, Bjorn Andersson wrote:
> On Thu 05 Apr 09:18 PDT 2018, Lina Iyer wrote:
> > diff --git a/drivers/soc/qcom/rpmh-internal.h b/drivers/soc/qcom/rpmh-internal.h
> [..]
> > @@ -439,6 +445,107 @@ int rpmh_rsc_send_data(struct rsc_drv *drv, const struct tcs_request *msg)
> >  }
> >  EXPORT_SYMBOL(rpmh_rsc_send_data);
> >
> > +static int find_match(const struct tcs_group *tcs, const struct tcs_cmd *cmd,
> > +		      int len)
> > +{
> > +	int i, j;
> > +
> > +	/* Check for already cached commands */
> > +	for_each_set_bit(i, tcs->slots, MAX_TCS_SLOTS) {
>
> Wouldn't it be good if this cared about TCS boundaries?
A sequence would never cross a TCS boundary. So it doesn't need to be
checked.

> > +		for (j = 0; j < len; j++) {
> > +			if (tcs->cmd_cache[i] != cmd[0].addr) {
> > +				if (j == 0)
> > +					break;
> > +				WARN(tcs->cmd_cache[i + j] != cmd[j].addr,
> > +				     "Message does not match previous sequence.\n");
> > +				return -EINVAL;
> > +			} else if (j == len - 1) {
> > +				return i;
> > +			}
> > +		}
> > +	}
> > +
> > +	return -ENODATA;
> > +}
> > +
> > +static int find_slots(struct tcs_group *tcs, const struct tcs_request *msg,
> > +		      int *m, int *n)
> > +{
> > +	int slot, offset;
> > +	int i = 0;
> > +
> > +	/* Find if we already have the msg in our TCS */
>
> "Search for the sequence of addresses in our tcs group"
OK
> > +	slot = find_match(tcs, msg->cmds, msg->num_cmds);
> > +	if (slot >= 0)
> > +		goto copy_data;
> > +
> > +	/* Do over, until we can fit the full payload in a TCS */
> > +	do {
> > +		slot = bitmap_find_next_zero_area(tcs->slots, MAX_TCS_SLOTS,
> > +						  i, msg->num_cmds, 0);
> > +		if (slot == MAX_TCS_SLOTS)
> > +			return -ENOMEM;
> > +		i += tcs->ncpt;
> > +	} while (slot + msg->num_cmds - 1 >= i);
>
> Does this conditional check that the sequence of free slots that we
> found doesn't extend past the boundary of a TCS?
Yes, it does.

> I'm sorry, but this code is hard to understand. I would find this much
> easier to read if there was one bitmap per TCS and you just looped over
> them to find free regions.
Hmm, its too many bitmaps otherwise.

> > +
> > +copy_data:
> > +	bitmap_set(tcs->slots, slot, msg->num_cmds);
> > +	/* Copy the addresses of the resources over to the slots */
> > +	for (i = 0; i < msg->num_cmds; i++)
> > +		tcs->cmd_cache[slot + i] = msg->cmds[i].addr;
> > +
> > +	offset = slot / tcs->ncpt;
> > +	*m = offset + tcs->offset;
> > +	*n = slot % tcs->ncpt;
> > +
> > +	return 0;
> > +}
> > +
> > +static int tcs_ctrl_write(struct rsc_drv *drv, const struct tcs_request *msg)
> > +{
> > +	struct tcs_group *tcs;
> > +	int m = 0, n = 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);
> > +	/* find the m-th TCS and the n-th position in the TCS to write to */
> > +	ret = find_slots(tcs, msg, &m, &n);
> > +	if (!ret)
> > +		__tcs_buffer_write(drv, m, n, msg);
> > +	spin_unlock_irqrestore(&tcs->lock, flags);
> > +
> > +	return ret;
> > +}
> > +
> > +/**
> > + * rpmh_rsc_write_ctrl_data: Write request to the controller
> > + *
> > + * @drv: the controller
> > + * @msg: the data to be written to the controller
> > + *
> > + * There is no response returned for writing the request to the controller.
> > + */
> > +int rpmh_rsc_write_ctrl_data(struct rsc_drv *drv, const struct tcs_request *msg)
>
> So this is exactly the same thing as rpmh_rsc_send_data() but for one of
> the non-active TCSs?
Yes.
> Can't we have a single API for writing msg to the hardware and if it's
> active we "send" it as well?
Hmm.. It can be done.

> > +{
> > +	if (!msg || !msg->cmds || !msg->num_cmds ||
> > +	    msg->num_cmds > MAX_RPMH_PAYLOAD) {
> > +		pr_err("Payload error\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	/* Data sent to this API will not be sent immediately */
> > +	if (msg->state == RPMH_ACTIVE_ONLY_STATE)
> > +		return -EINVAL;
>
> If you're concerned about this then the API isn't clear enough.
>
> > +
> > +	return tcs_ctrl_write(drv, msg);
> > +}
> > +EXPORT_SYMBOL(rpmh_rsc_write_ctrl_data);
> > +
> >  static int rpmh_probe_tcs_config(struct platform_device *pdev,
> >  				 struct rsc_drv *drv)
> >  {
> > @@ -512,6 +619,19 @@ static int rpmh_probe_tcs_config(struct platform_device *pdev,
> >  		tcs->mask = ((1 << tcs->num_tcs) - 1) << st;
> >  		tcs->offset = st;
> >  		st += tcs->num_tcs;
> > +
> > +		/*
> > +		 * Allocate memory to cache sleep and wake requests to
> > +		 * avoid reading TCS register memory.
> > +		 */
> > +		if (tcs->type == ACTIVE_TCS)
> > +			continue;
>
> Rather than "the rest of this loop shouldn't be done for the active tcs
> group" just make another loop... Or at least make the comment relate
> directly to the code it's adjacent.
Will move the comment out.
> > +
> > +		tcs->cmd_cache = devm_kcalloc(&pdev->dev,
> > +					      tcs->num_tcs * ncpt, sizeof(u32),
> > +					      GFP_KERNEL);
> > +		if (!tcs->cmd_cache)
> > +			return -ENOMEM;

Thanks for the review Bjorn.

-- Lina