Hi, Gunenadi
On 11/26/2014 6:21 AM, Guennadi Liakhovetski wrote:
Hi Josh,
On Tue, 25 Nov 2014, Josh Wu wrote:
The burst length could be BEATS_4/8/16. Before this patch, isi use default
value BEATS_4. To imporve the performance we could set it to BEATS_16.
Otherwise sometime it would cause the ISI overflow error.
Without looking at datasheets - what does this bit do? Change the transfer
length?
Atmel ISI has two internal 32-bytes FIFOs, one for Preview, another for
Codec.
This field is the threshold to trigger the FIFO transfer to AHB by DMA.
We can set the threshold to allow 4-bytes, 8-bytes or 16-bytes for a burst.
BEATS_4, means only allow 4-bytes in a burst.
BEATS_8, means only allow 4-bytes and 8-bytes in a burst.
BEATS_16, means allow 4-bytes, 8-bytes and 16-bytes in a burst.
So BEATS_16 will use the DMA more efficient if has lots of data to
transfer. As we are allowed to use 16-bytes in a burst. That will
trigger less burst than BEATS_4 to transfer same amount of data.
We found this patch can fix ISI FIFO overflow error when system is in a
situation that with a very high memory load.
If we only allow 4-bytes in a burst, that need more burst to transfer
data and less effective.
What happens then if the data amount isn't a multiple of the
transfer size?
BEATS_16 means allowed 4-bytes, 8-bytes and 16-bytes in a burst. So it
still can perform a 4-bytes transfer if the data is not multiple of 16.
I think all the data transfer are aligned with 4 bytes. The DMA address
should be aligned with 4 bytes as well.
Best Regards,
Josh Wu
Thanks
Guennadi
Reported-by: Bo Shen <voice.s...@atmel.com>
Signed-off-by: Josh Wu <josh...@atmel.com>
---
drivers/media/platform/soc_camera/atmel-isi.c | 2 ++
include/media/atmel-isi.h | 4 ++++
2 files changed, 6 insertions(+)
diff --git a/drivers/media/platform/soc_camera/atmel-isi.c
b/drivers/media/platform/soc_camera/atmel-isi.c
index ee5650f..fda587b 100644
--- a/drivers/media/platform/soc_camera/atmel-isi.c
+++ b/drivers/media/platform/soc_camera/atmel-isi.c
@@ -839,6 +839,8 @@ static int isi_camera_set_bus_param(struct
soc_camera_device *icd)
if (isi->pdata.full_mode)
cfg1 |= ISI_CFG1_FULL_MODE;
+ cfg1 |= ISI_CFG1_THMASK_BEATS_16;
+
isi_writel(isi, ISI_CTRL, ISI_CTRL_DIS);
isi_writel(isi, ISI_CFG1, cfg1);
diff --git a/include/media/atmel-isi.h b/include/media/atmel-isi.h
index c2e5703..6008b09 100644
--- a/include/media/atmel-isi.h
+++ b/include/media/atmel-isi.h
@@ -59,6 +59,10 @@
#define ISI_CFG1_FRATE_DIV_MASK (7 << 8)
#define ISI_CFG1_DISCR (1 << 11)
#define ISI_CFG1_FULL_MODE (1 << 12)
+/* Definition for THMASK(ISI_V2) */
+#define ISI_CFG1_THMASK_BEATS_4 (0 << 13)
+#define ISI_CFG1_THMASK_BEATS_8 (1 << 13)
+#define ISI_CFG1_THMASK_BEATS_16 (2 << 13)
/* Bitfields in CFG2 */
#define ISI_CFG2_GRAYSCALE (1 << 13)
--
1.9.1
--
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