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Date:   Wed, 24 Oct 2018 11:07:16 -0600
From:   Lina Iyer <ilina@codeaurora.org>
To:     "Raju P.L.S.S.S.N" <rplsssn@codeaurora.org>
Cc:     andy.gross@linaro.org, david.brown@linaro.org,
        linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org,
        rnayak@codeaurora.org, bjorn.andersson@linaro.org,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        sboyd@kernel.org, evgreen@chromium.org, dianders@chromium.org,
        mka@chromium.org
Subject: Re: [PATCH v3 1/3] drivers: qcom: rpmh-rsc: simplify TCS locking
Message-ID: <20181024170716.GF17444@codeaurora.org>
References: <1539050912-25749-1-git-send-email-rplsssn@codeaurora.org>
 <1539050912-25749-2-git-send-email-rplsssn@codeaurora.org>
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In-Reply-To: <1539050912-25749-2-git-send-email-rplsssn@codeaurora.org>
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Sender: linux-kernel-owner@vger.kernel.org
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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@codeaurora.org>
>Signed-off-by: Raju P.L.S.S.S.N <rplsssn@codeaurora.org>
Reviewed-by: Lina Iyer <ilina@codeaurora.org>

>---
>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.
>