[PATCH 07/10] dmaengine: qcom_hidma: eliminate processed variables

Sinan Kaya
2016-07-18T18:40:49Z

Instead of tracking the read/write pointers in SW, track the
current state by reading from HW directly. This is an attempt
to eliminate potential race conditions.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
---
drivers/dma/qcom/hidma.h | 5 +++--
drivers/dma/qcom/hidma_dbg.c | 6 ++++--
drivers/dma/qcom/hidma_ll.c | 29 +++++++----------------------
3 files changed, 14 insertions(+), 26 deletions(-)

diff --git a/drivers/dma/qcom/hidma.h b/drivers/dma/qcom/hidma.h
index 158bf1f..03c20f6 100644
--- a/drivers/dma/qcom/hidma.h
+++ b/drivers/dma/qcom/hidma.h
@@ -28,6 +28,9 @@
#define HIDMA_TRE_DEST_LOW_IDX 4
#define HIDMA_TRE_DEST_HI_IDX 5

+#define HIDMA_EVCA_READ_PTR_REG 0x018
+#define HIDMA_TRCA_READ_PTR_REG 0x018
+
struct hidma_tre {
atomic_t allocated; /* if this channel is allocated */
bool queued; /* flag whether this is pending */
@@ -63,12 +66,10 @@ struct hidma_lldev {
void *tre_ring; /* TRE ring */
dma_addr_t tre_dma; /* TRE ring to be shared with HW */
u32 tre_ring_size; /* Byte size of the ring */
- u32 tre_processed_off; /* last processed TRE */

void *evre_ring; /* EVRE ring */
dma_addr_t evre_dma; /* EVRE ring to be shared with HW */
u32 evre_ring_size; /* Byte size of the ring */
- u32 evre_processed_off; /* last processed EVRE */

u32 tre_write_offset; /* TRE write location */
struct tasklet_struct task; /* task delivering notifications */
diff --git a/drivers/dma/qcom/hidma_dbg.c b/drivers/dma/qcom/hidma_dbg.c
index 87db285..d741b9d 100644
--- a/drivers/dma/qcom/hidma_dbg.c
+++ b/drivers/dma/qcom/hidma_dbg.c
@@ -73,14 +73,16 @@ static void hidma_ll_devstats(struct seq_file *s, void *llhndl)
seq_printf(s, "tre_ring=%p\n", lldev->tre_ring);
seq_printf(s, "tre_ring_handle=%pap\n", &lldev->tre_dma);
seq_printf(s, "tre_ring_size = 0x%x\n", lldev->tre_ring_size);
- seq_printf(s, "tre_processed_off = 0x%x\n", lldev->tre_processed_off);
+ seq_printf(s, "tre_processed_off = 0x%x\n",
+ readl(lldev->trca + HIDMA_TRCA_READ_PTR_REG));
seq_printf(s, "pending_tre_count=%d\n",
atomic_read(&lldev->pending_tre_count));
seq_printf(s, "evca=%p\n", lldev->evca);
seq_printf(s, "evre_ring=%p\n", lldev->evre_ring);
seq_printf(s, "evre_ring_handle=%pap\n", &lldev->evre_dma);
seq_printf(s, "evre_ring_size = 0x%x\n", lldev->evre_ring_size);
- seq_printf(s, "evre_processed_off = 0x%x\n", lldev->evre_processed_off);
+ seq_printf(s, "evre_processed_off = 0x%x\n",
+ readl(lldev->evca + HIDMA_EVCA_READ_PTR_REG));
seq_printf(s, "tre_write_offset = 0x%x\n", lldev->tre_write_offset);
}

diff --git a/drivers/dma/qcom/hidma_ll.c b/drivers/dma/qcom/hidma_ll.c
index a71f0c7..2753210 100644
--- a/drivers/dma/qcom/hidma_ll.c
+++ b/drivers/dma/qcom/hidma_ll.c
@@ -245,13 +245,13 @@ static int hidma_handle_tre_completion(struct hidma_lldev *lldev, u8 err_info,
u8 err_code)
{
u32 evre_ring_size = lldev->evre_ring_size;
- u32 tre_ring_size = lldev->tre_ring_size;
+ u32 evre_write_off;
u32 tre_iterator, evre_iterator;
u32 num_completed = 0;

evre_write_off = readl_relaxed(lldev->evca + HIDMA_EVCA_WRITE_PTR_REG);
- tre_iterator = lldev->tre_processed_off;
- evre_iterator = lldev->evre_processed_off;
+ evre_iterator = readl_relaxed(lldev->evca + HIDMA_EVCA_READ_PTR_REG);
+ tre_iterator = (evre_iterator / HIDMA_EVRE_SIZE) * HIDMA_TRE_SIZE;

if ((evre_write_off > evre_ring_size) ||
(evre_write_off % HIDMA_EVRE_SIZE)) {
@@ -280,10 +280,10 @@ static int hidma_handle_tre_completion(struct hidma_lldev *lldev, u8 err_info,
err_code))
break;

- HIDMA_INCREMENT_ITERATOR(tre_iterator, HIDMA_TRE_SIZE,
- tre_ring_size);
HIDMA_INCREMENT_ITERATOR(evre_iterator, HIDMA_EVRE_SIZE,
evre_ring_size);
+ tre_iterator = (evre_iterator / HIDMA_EVRE_SIZE) *
+ HIDMA_TRE_SIZE;

/*
* Read the new event descriptor written by the HW.
@@ -295,21 +295,8 @@ static int hidma_handle_tre_completion(struct hidma_lldev *lldev, u8 err_info,
num_completed++;
}

- if (num_completed) {
- u32 evre_read_off = (lldev->evre_processed_off +
- HIDMA_EVRE_SIZE * num_completed);
- u32 tre_read_off = (lldev->tre_processed_off +
- HIDMA_TRE_SIZE * num_completed);
-
- evre_read_off = evre_read_off % evre_ring_size;
- tre_read_off = tre_read_off % tre_ring_size;
-
- writel(evre_read_off, lldev->evca + HIDMA_EVCA_DOORBELL_REG);
-
- /* record the last processed tre offset */
- lldev->tre_processed_off = tre_read_off;
- lldev->evre_processed_off = evre_read_off;
- }
+ if (num_completed)
+ writel(evre_iterator, lldev->evca + HIDMA_EVCA_DOORBELL_REG);

return num_completed;
}
@@ -654,8 +641,6 @@ int hidma_ll_setup(struct hidma_lldev *lldev)
u32 nr_tres = lldev->nr_tres;

atomic_set(&lldev->pending_tre_count, 0);
- lldev->tre_processed_off = 0;
- lldev->evre_processed_off = 0;
lldev->tre_write_offset = 0;

/* disable interrupts */
--
1.8.2.1