Re: [PATCH v3 1/3] drivers: qcom: rpmh-rsc: simplify TCS locking

Lina Iyer <ilina@xxxxxxxxxxxxxx> · Wed, 24 Oct 2018 11:07:16 -0600

On Tue, Oct 09 2018 at 20:08 -0600, Raju P.L.S.S.S.N wrote:
tcs->lock was introduced to serialize access with in TCS group. But
even without tcs->lock, drv->lock is serving the same purpose. So
use single drv->lock.

Other optimizations include -
- Remove locking around clear_bit() in IRQ handler. clear_bit() is
  atomic.
- Remove redundant read of TCS registers.
- Use spin_lock instead of _irq variants as the locks are not held
  in interrupt context

Suggested-by: Lina Iyer <ilina@xxxxxxxxxxxxxx>
Signed-off-by: Raju P.L.S.S.S.N <rplsssn@xxxxxxxxxxxxxx>
Reviewed-by: Lina Iyer <ilina@xxxxxxxxxxxxxx>

---
This patch is based on https://lkml.org/lkml/2018/10/3/422
---
drivers/soc/qcom/rpmh-internal.h |  2 --
drivers/soc/qcom/rpmh-rsc.c      | 37 +++++++++++++------------------------
drivers/soc/qcom/rpmh.c          | 20 ++++++++------------
3 files changed, 21 insertions(+), 38 deletions(-)

diff --git a/drivers/soc/qcom/rpmh-internal.h b/drivers/soc/qcom/rpmh-internal.h
index 8c316b4..2e3ffcd 100644
--- a/drivers/soc/qcom/rpmh-internal.h
+++ b/drivers/soc/qcom/rpmh-internal.h
@@ -28,7 +28,6 @@
 * @offset:    start of the TCS group relative to the TCSes in the RSC
 * @num_tcs:   number of TCSes in this type
 * @ncpt:      number of commands in each TCS
- * @lock:      lock for synchronizing this TCS writes
 * @req:       requests that are sent from the TCS
 * @cmd_cache: flattened cache of cmds in sleep/wake TCS
 * @slots:     indicates which of @cmd_addr are occupied
@@ -40,7 +39,6 @@ struct tcs_group {
	u32 offset;
	int num_tcs;
	int ncpt;
-	spinlock_t lock;
	const struct tcs_request *req[MAX_TCS_PER_TYPE];
	u32 *cmd_cache;
	DECLARE_BITMAP(slots, MAX_TCS_SLOTS);
diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
index 73d5b98..d6b834e 100644
--- a/drivers/soc/qcom/rpmh-rsc.c
+++ b/drivers/soc/qcom/rpmh-rsc.c
@@ -98,8 +98,7 @@ static void write_tcs_reg_sync(struct rsc_drv *drv, int reg, int tcs_id,

static bool tcs_is_free(struct rsc_drv *drv, int tcs_id)
{
-	return !test_bit(tcs_id, drv->tcs_in_use) &&
-	       read_tcs_reg(drv, RSC_DRV_STATUS, tcs_id, 0);
+	return !test_bit(tcs_id, drv->tcs_in_use);
}

static struct tcs_group *get_tcs_of_type(struct rsc_drv *drv, int type)
@@ -109,29 +108,28 @@ static struct tcs_group *get_tcs_of_type(struct rsc_drv *drv, int type)

static int tcs_invalidate(struct rsc_drv *drv, int type)
{
-	int m;
+	int m, ret = 0;
	struct tcs_group *tcs;

	tcs = get_tcs_of_type(drv, type);

-	spin_lock(&tcs->lock);
-	if (bitmap_empty(tcs->slots, MAX_TCS_SLOTS)) {
-		spin_unlock(&tcs->lock);
-		return 0;
-	}
+	spin_lock(&drv->lock);
+	if (bitmap_empty(tcs->slots, MAX_TCS_SLOTS))
+		goto done;

	for (m = tcs->offset; m < tcs->offset + tcs->num_tcs; m++) {
		if (!tcs_is_free(drv, m)) {
-			spin_unlock(&tcs->lock);
-			return -EAGAIN;
+			ret = -EAGAIN;
+			goto done;
		}
		write_tcs_reg_sync(drv, RSC_DRV_CMD_ENABLE, m, 0);
		write_tcs_reg_sync(drv, RSC_DRV_CMD_WAIT_FOR_CMPL, m, 0);
	}
	bitmap_zero(tcs->slots, MAX_TCS_SLOTS);
-	spin_unlock(&tcs->lock);

-	return 0;
+done:
+	spin_unlock(&drv->lock);
+	return ret;
}

/**
@@ -298,9 +296,7 @@ static irqreturn_t tcs_tx_done(int irq, void *p)
		write_tcs_reg(drv, RSC_DRV_CMD_ENABLE, i, 0);
		write_tcs_reg(drv, RSC_DRV_CMD_WAIT_FOR_CMPL, i, 0);
		write_tcs_reg(drv, RSC_DRV_IRQ_CLEAR, 0, BIT(i));
-		spin_lock(&drv->lock);
		clear_bit(i, drv->tcs_in_use);
-		spin_unlock(&drv->lock);
		if (req)
			rpmh_tx_done(req, err);
	}
@@ -383,14 +379,12 @@ 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,
@@ -398,14 +392,12 @@ static int tcs_write(struct rsc_drv *drv, const struct tcs_request *msg)
	 */
	ret = check_for_req_inflight(drv, tcs, msg);
	if (ret) {
-		spin_unlock(&drv->lock);
		goto done_write;
	}

	tcs_id = find_free_tcs(tcs);
	if (tcs_id < 0) {
		ret = tcs_id;
-		spin_unlock(&drv->lock);
		goto done_write;
	}

@@ -413,13 +405,12 @@ static int tcs_write(struct rsc_drv *drv, const struct tcs_request *msg)
	set_bit(tcs_id, drv->tcs_in_use);
	if (msg->state == RPMH_ACTIVE_ONLY_STATE && tcs->type != ACTIVE_TCS)
		enable_tcs_irq(drv, tcs_id, true);
-	spin_unlock(&drv->lock);

	__tcs_buffer_write(drv, tcs_id, 0, msg);
	__tcs_trigger(drv, tcs_id, true);

done_write:
-	spin_unlock_irqrestore(&tcs->lock, flags);
+	spin_unlock(&drv->lock);
	return ret;
}

@@ -517,19 +508,18 @@ 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);

	return ret;
}
@@ -638,7 +628,6 @@ static int rpmh_probe_tcs_config(struct platform_device *pdev,
		tcs->type = tcs_cfg[i].type;
		tcs->num_tcs = tcs_cfg[i].n;
		tcs->ncpt = ncpt;
-		spin_lock_init(&tcs->lock);

		if (!tcs->num_tcs || tcs->type == CONTROL_TCS)
			continue;
diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
index 71a76ea..297d6cc 100644
--- a/drivers/soc/qcom/rpmh.c
+++ b/drivers/soc/qcom/rpmh.c
@@ -117,9 +117,8 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
					   struct tcs_cmd *cmd)
{
	struct cache_req *req;
-	unsigned long flags;

-	spin_lock_irqsave(&ctrlr->cache_lock, flags);
+	spin_lock(&ctrlr->cache_lock);
	req = __find_req(ctrlr, cmd->addr);
	if (req)
		goto existing;
@@ -153,7 +152,7 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,

	ctrlr->dirty = true;
unlock:
-	spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+	spin_unlock(&ctrlr->cache_lock);

	return req;
}
@@ -283,23 +282,21 @@ int rpmh_write(const struct device *dev, enum rpmh_state state,

static void cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
{
-	unsigned long flags;

-	spin_lock_irqsave(&ctrlr->cache_lock, flags);
+	spin_lock(&ctrlr->cache_lock);
	list_add_tail(&req->list, &ctrlr->batch_cache);
-	spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+	spin_unlock(&ctrlr->cache_lock);
}

static int flush_batch(struct rpmh_ctrlr *ctrlr)
{
	struct batch_cache_req *req;
	const struct rpmh_request *rpm_msg;
-	unsigned long flags;
	int ret = 0;
	int i;

	/* Send Sleep/Wake requests to the controller, expect no response */
-	spin_lock_irqsave(&ctrlr->cache_lock, flags);
+	spin_lock(&ctrlr->cache_lock);
	list_for_each_entry(req, &ctrlr->batch_cache, list) {
		for (i = 0; i < req->count; i++) {
			rpm_msg = req->rpm_msgs + i;
@@ -309,7 +306,7 @@ static int flush_batch(struct rpmh_ctrlr *ctrlr)
				break;
		}
	}
-	spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+	spin_unlock(&ctrlr->cache_lock);

	return ret;
}
@@ -317,13 +314,12 @@ static int flush_batch(struct rpmh_ctrlr *ctrlr)
static void invalidate_batch(struct rpmh_ctrlr *ctrlr)
{
	struct batch_cache_req *req, *tmp;
-	unsigned long flags;

-	spin_lock_irqsave(&ctrlr->cache_lock, flags);
+	spin_lock(&ctrlr->cache_lock);
	list_for_each_entry_safe(req, tmp, &ctrlr->batch_cache, list)
		kfree(req);
	INIT_LIST_HEAD(&ctrlr->batch_cache);
-	spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+	spin_unlock(&ctrlr->cache_lock);
}

/**
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of the Code Aurora Forum, hosted by The Linux Foundation.







