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Subject[PATCH 3/5] bus: mhi: host: Use {READ/WITE}_ONCE macros for db_mode and db_val
Date
In order to prevent the compiler from optimizing these fields that could
be used parallely, let's use the {READ/WRITE}_ONCE macros for reading and
updating. Since these fields are defined as bool, let's use the true/false
instead of 0/1.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
drivers/bus/mhi/host/init.c | 4 ++--
drivers/bus/mhi/host/main.c | 14 +++++++++-----
2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
index e095d2999c06..906bdf584860 100644
--- a/drivers/bus/mhi/host/init.c
+++ b/drivers/bus/mhi/host/init.c
@@ -325,7 +325,7 @@ int mhi_init_dev_ctxt(struct mhi_controller *mhi_cntrl)

er_ctxt->ertype = cpu_to_le32(MHI_ER_TYPE_VALID);
er_ctxt->msivec = cpu_to_le32(mhi_event->irq);
- mhi_event->db_cfg.db_mode = true;
+ WRITE_ONCE(mhi_event->db_cfg.db_mode, true);

ring->el_size = sizeof(struct mhi_ring_element);
ring->len = ring->el_size * ring->elements;
@@ -615,7 +615,7 @@ int mhi_init_chan_ctxt(struct mhi_controller *mhi_cntrl,

tre_ring->rp = tre_ring->wp = tre_ring->base;
buf_ring->rp = buf_ring->wp = buf_ring->base;
- mhi_chan->db_cfg.db_mode = 1;
+ WRITE_ONCE(mhi_chan->db_cfg.db_mode, true);

/* Update to all cores */
smp_wmb();
diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index 28b41621e004..bb3b20207c4e 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -92,10 +92,14 @@ void mhi_ring_db_brstmode(struct mhi_controller *mhi_cntrl,
void __iomem *db_addr,
dma_addr_t db_val)
{
- if (db_cfg->db_mode) {
- db_cfg->db_val = db_val;
+ if (READ_ONCE(db_cfg->db_mode)) {
+ /*
+ * There is no barrier required here, since both compiler and
+ * CPU will honor the load/store control dependency.
+ */
+ WRITE_ONCE(db_cfg->db_val, db_val);
mhi_write_db(mhi_cntrl, db_addr, db_val);
- db_cfg->db_mode = 0;
+ WRITE_ONCE(db_cfg->db_mode, false);
}
}

@@ -104,7 +108,7 @@ void mhi_ring_db_no_brstmode(struct mhi_controller *mhi_cntrl,
void __iomem *db_addr,
dma_addr_t db_val)
{
- db_cfg->db_val = db_val;
+ WRITE_ONCE(db_cfg->db_val, db_val);
mhi_write_db(mhi_cntrl, db_addr, db_val);
}

@@ -665,7 +669,7 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
{
unsigned long pm_lock_flags;

- mhi_chan->db_cfg.db_mode = 1;
+ WRITE_ONCE(mhi_chan->db_cfg.db_mode, true);
read_lock_irqsave(&mhi_cntrl->pm_lock, pm_lock_flags);
if (tre_ring->wp != tre_ring->rp &&
MHI_DB_ACCESS_VALID(mhi_cntrl)) {
--
2.25.1
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