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

From: Lina Iyer
Date: Wed Oct 24 2018 - 13:07:22 EST

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);
}

/**
--
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