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SubjectRe: [PATCH v3 09/10] drivers: qcom: rpmh: add support for batch RPMH request
Date
Quoting Lina Iyer (2018-03-02 08:43:16)
> diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
> index a02d9f685b2b..19e84b031c0d 100644
> --- a/drivers/soc/qcom/rpmh.c
> +++ b/drivers/soc/qcom/rpmh.c
> @@ -22,6 +22,7 @@
>
> #define RPMH_MAX_MBOXES 2
> #define RPMH_TIMEOUT (10 * HZ)
> +#define RPMH_MAX_REQ_IN_BATCH 10

Is 10 some software limit? Or hardware always has 10 available?

>
> #define DEFINE_RPMH_MSG_ONSTACK(rc, s, q, c, name) \
> struct rpmh_request name = { \
> @@ -81,12 +82,14 @@ struct rpmh_request {
> * @cache: the list of cached requests
> * @lock: synchronize access to the controller data
> * @dirty: was the cache updated since flush
> + * @batch_cache: Cache sleep and wake requests sent as batch
> */
> struct rpmh_ctrlr {
> struct rsc_drv *drv;
> struct list_head cache;
> spinlock_t lock;
> bool dirty;
> + struct rpmh_request *batch_cache[2 * RPMH_MAX_REQ_IN_BATCH];

Can it be const?

> };
>
> /**
> @@ -343,6 +346,146 @@ int rpmh_write(struct rpmh_client *rc, enum rpmh_state state,
> }
> EXPORT_SYMBOL(rpmh_write);
>
> +static int cache_batch(struct rpmh_client *rc,
> + struct rpmh_request **rpm_msg, int count)
> +{
> + struct rpmh_ctrlr *rpm = rc->ctrlr;
> + unsigned long flags;
> + int ret = 0;
> + int index = 0;
> + int i;
> +
> + spin_lock_irqsave(&rpm->lock, flags);
> + while (rpm->batch_cache[index])

If batch_cache is full.
And if adjacent memory has bits set....

This loop can go forever?

Please add bounds.

> + index++;
> + if (index + count >= 2 * RPMH_MAX_REQ_IN_BATCH) {
> + ret = -ENOMEM;
> + goto fail;
> + }
> +
> + for (i = 0; i < count; i++)
> + rpm->batch_cache[index + i] = rpm_msg[i];
> +fail:
> + spin_unlock_irqrestore(&rpm->lock, flags);
> +
> + return ret;
> +}
> +
[...]
> +static void invalidate_batch(struct rpmh_client *rc)
> +{
> + struct rpmh_ctrlr *rpm = rc->ctrlr;
> + unsigned long flags;
> + int index = 0;
> + int i;
> +
> + spin_lock_irqsave(&rpm->lock, flags);
> + while (rpm->batch_cache[index])
> + index++;
> + for (i = 0; i < index; i++) {
> + kfree(rpm->batch_cache[i]->free);
> + rpm->batch_cache[i] = NULL;
> + }
> + spin_unlock_irqrestore(&rpm->lock, flags);
> +}
> +
> +/**
> + * rpmh_write_batch: Write multiple sets of RPMH commands and wait for the
> + * batch to finish.
> + *
> + * @rc: The RPMh handle got from rpmh_get_dev_channel

Is the API called rpmh_get_dev_channel()?

> + * @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 mailbox 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(struct rpmh_client *rc, enum rpmh_state state,
> + struct tcs_cmd *cmd, int *n)

I'm lost why n is a pointer, and cmd is not a double pointer if n stays
as a pointer. Are there clients calling this API with a contiguous chunk
of commands but then they want to break that chunk up into many
requests? Maybe I've lost track of commands and requests and how they
differ.

> +{
> + struct rpmh_request *rpm_msg[RPMH_MAX_REQ_IN_BATCH] = { NULL };
> + DECLARE_COMPLETION_ONSTACK(compl);
> + atomic_t wait_count = ATOMIC_INIT(0); /* overwritten */
> + int count = 0;
> + int ret, i, j;
> +
> + if (IS_ERR_OR_NULL(rc) || !cmd || !n)
> + return -EINVAL;
> +
> + while (n[count++] > 0)
> + ;
> + count--;
> + if (!count || count > RPMH_MAX_REQ_IN_BATCH)
> + return -EINVAL;
> +
> + /* Create async request batches */
> + for (i = 0; i < count; i++) {
> + rpm_msg[i] = __get_rpmh_msg_async(rc, state, cmd, n[i]);
> + if (IS_ERR_OR_NULL(rpm_msg[i])) {
> + for (j = 0 ; j < i; j++)

Weird space before that ;

Also, why not use 'i' again and decrement? ret could be assigned
PTR_ERR() value and make the next potential problem go away.

> + kfree(rpm_msg[j]->free);

I hope rpm_msg[j]->free doesn't point to rpm_msg[i] here.

> + return PTR_ERR(rpm_msg[i]);
> + }
> + cmd += n[i];
> + }
> +
> + /* Send if Active and wait for the whole set to complete */
> + if (state == RPMH_ACTIVE_ONLY_STATE) {
> + might_sleep();
> + atomic_set(&wait_count, count);

Aha, here's the wait counter.

> + for (i = 0; i < count; i++) {
> + rpm_msg[i]->completion = &compl;
> + rpm_msg[i]->wait_count = &wait_count;

But then we just assign the same count and completion to each rpm_msg?
Why? Can't we just put the completion on the final one and have the
completion called there?

> + /* Bypass caching and write to mailbox directly */
> + ret = rpmh_rsc_send_data(rc->ctrlr->drv,
> + &rpm_msg[i]->msg);
> + if (ret < 0) {
> + pr_err(
> + "Error(%d) sending RPMH message addr=0x%x\n",
> + ret, rpm_msg[i]->msg.payload[0].addr);
> + break;
> + }
> + }
> + /* For those unsent requests, spoof tx_done */

Why? Comments shouldn't say what the code is doing, but explain why
things don't make sense.

> + for (j = i; j < count; j++)
> + rpmh_tx_done(&rpm_msg[j]->msg, ret);
> + return wait_for_tx_done(rc, &compl, cmd[0].addr, cmd[0].data);
> + }
> +
> + /*
> + * Cache sleep/wake data in store.
> + * But flush batch first before flushing all other data.
> + */
> + return cache_batch(rc, rpm_msg, count);

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