linux-kernel - Re: [PATCH v9 09/10] drivers: qcom: rpmh: add support for batch RPMH request

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Date:   Wed, 30 May 2018 14:50:01 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Raju P L S S S N <rplsssn@...eaurora.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        linux-arm-msm@...r.kernel.org,
        "open list:ARM/QUALCOMM SUPPORT" <linux-soc@...r.kernel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Evan Green <evgreen@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Lina Iyer <ilina@...eaurora.org>
Subject: Re: [PATCH v9 09/10] drivers: qcom: rpmh: add support for batch RPMH request

Hi,

On Thu, May 24, 2018 at 3:45 AM, Raju P L S S S N
<rplsssn@...eaurora.org> wrote:
>  #define DEFINE_RPMH_MSG_ONSTACK(dev, s, q, name)       \
>         struct rpmh_request name = {                    \
> @@ -35,6 +37,7 @@
>                 .completion = q,                        \
>                 .dev = dev,                             \
>                 .needs_free = false,                            \
> +               .wait_count = NULL,                     \

You ignored my feedback on v8 that wait_count is not useful.  Please
squash in <http://crosreview.com/1079905>.  That also has a fix where
it introduces a WARN_ON for the timeout case in batch mode too.


> +/**
> + * rpmh_write_batch: Write multiple sets of RPMH commands and wait for the
> + * batch to finish.
> + *
> + * @dev: the device making the request
> + * @state: Active/sleep set
> + * @cmd: The payload data
> + * @n: The array of count of elements in each batch, 0 terminated.
> + *
> + * Write a request to the RSC controller without caching. If the request
> + * state is ACTIVE, then the requests are treated as completion request
> + * and sent to the controller immediately. The function waits until all the
> + * commands are complete. If the request was to SLEEP or WAKE_ONLY, then the
> + * request is sent as fire-n-forget and no ack is expected.
> + *
> + * May sleep. Do not call from atomic contexts for ACTIVE_ONLY requests.
> + */
> +int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
> +                    const struct tcs_cmd *cmd, u32 *n)
> +{
> +       struct rpmh_request *rpm_msg[RPMH_MAX_REQ_IN_BATCH] = { NULL };
> +       DECLARE_COMPLETION_ONSTACK(compl);
> +       atomic_t wait_count = ATOMIC_INIT(0);
> +       struct rpmh_ctrlr *ctrlr = get_rpmh_ctrlr(dev);
> +       int count = 0;
> +       int ret, i, j;
> +
> +       if (IS_ERR(ctrlr) || !cmd || !n)
> +               return -EINVAL;
> +
> +       while (n[count++] > 0)
> +               ;
> +       count--;
> +       if (!count || count > RPMH_MAX_REQ_IN_BATCH)
> +               return -EINVAL;
> +
> +       for (i = 0; i < count; i++) {
> +               rpm_msg[i] = __get_rpmh_msg_async(state, cmd, n[i]);
> +               if (IS_ERR(rpm_msg[i])) {
> +                       ret = PTR_ERR(rpm_msg[i]);
> +                       for (j = i-1; j >= 0; j--) {
> +                               if (rpm_msg[j]->needs_free)

How could needs_free be false here?


> +                                       kfree(rpm_msg[j]);
> +                       }
> +                       return ret;
> +               }
> +               cmd += n[i];
> +       }
> +
> +       if (state != RPMH_ACTIVE_ONLY_STATE)
> +               return cache_batch(ctrlr, rpm_msg, count);

Previously I said:
> Don't you need to free rpm_msg items in this case?

...but I think that wasn't clear enough.  Perhaps I should have said:

Don't you need to free rpm_msg items in the case where cache_batch
returns an error?  AKA squash in <http://crosreview.com/1079906>.


> +
> +       atomic_set(&wait_count, count);
> +
> +       for (i = 0; i < count; i++) {
> +               rpm_msg[i]->completion = &compl;
> +               rpm_msg[i]->wait_count = &wait_count;
> +               ret = rpmh_rsc_send_data(ctrlr->drv, &rpm_msg[i]->msg);
> +               if (ret) {
> +                       int j;

You're shadowing another "j" variable.  Please squash in
<http://crosreview.com/1080027>.

> +
> +                       pr_err("Error(%d) sending RPMH message addr=%#x\n",
> +                              ret, rpm_msg[i]->msg.cmds[0].addr);
> +                       for (j = i; j < count; j++)
> +                               rpmh_tx_done(&rpm_msg[j]->msg, ret);

Previously I said:

> Note that you'll probably do your error handling in this
> function a favor if you rename __get_rpmh_msg_async()
> to __fill_rpmh_msg() and remove the memory
> allocation from there

I tried to implement this but then I realized cache_batch() requires
individual allocation.  Sigh.

OK, I attempted this in <http://crosreview.com/1080028>.  This gets
rid of several static-sized arrays and gets rid of all of the little
memory allocations in rpmh_write_batch(), replacing it with one bigger
one.  In my mind this is an improvement, but I welcome other opinions.

As discussed previously, I'm still of the belief that we'll be better
off getting rid of separate "batch" data structures.  I'll see if I
can find some time to do that too and see how it looks.


-Doug