ECSPI has a low throughput because of no dynamic burst support, it
transfers only one word per frame in DMA mode, causing SCLK stalls
between words due to BURST_LENGTH updates.
This patch set is to support ECSPI dynamic burst feature to help improve
the ECSPI DMA mode performance.
Performance test (spidev_test @10MHz, 4KB):
Before: tx/rx ~6651.9 kbps
After: tx/rx ~9922.2 kbps (~50% improvement)
For compatibility with slow SPI devices, add configurable word delay in
DMA mode. When word delay is set, dynamic burst is disabled and
BURST_LENGTH equals word length.
Also support target DMA mode with enabled dynamic burst.
---
Changes since v2:
* Patch1~4: no change
* Patch5: remove __counted_by from *dma_data, because spi_imx struct
is allocated with a fixed memory in probe, flexible array is not
suitable, so just remove it to avoid the build error. Also add
review-by tag
* Patch6: add review-by tag
Changes since v1:
* Patch1~3:
* Add review-by tag
* Patch4:
* Add review-by tag
* Improve patch commit log
* Patch5:
* Clean up tab instead of space for dma_tx_addr and dma_rx_addr
* Add __counted_by(dma_package_num) for dma_data_package *dma_data
* Move temp and bytes_per_word to if()
* Add comment for spi_imx_dma_rx_data_handle() and
spi_imx_dma_tx_data_handle()
* Use kzalloc instead of kmalloc(x, x | __GFP_ZERO)
* Use sizeof(*temp) instead of BYTES_PER_32BITS_WORD in suitable place
* Add comments and fix comments according to discussion
* Propagate the error value of dma_mapping_error()
* Use round_down() to replace DIV_ROUND_DOWN_ULL()
* Improve transfer->error |= SPI_TRANS_FAIL_NO_START judgment for
better readability
* Patch6:
* Improve patch commit log
* Add READ_ONCE for spi_imx->target_aborted
* Add comments for data length limit
* Move data length limit to spi_imx_can_dma()
Carlos Song (6):
spi: imx: group spi_imx_dma_configure() with spi_imx_dma_transfer()
spi: imx: introduce helper to clear DMA mode logic
spi: imx: avoid dmaengine_terminate_all() on TX prep failure
spi: imx: handle DMA submission errors with dma_submit_error()
spi: imx: support dynamic burst length for ECSPI DMA mode
spi: imx: enable DMA mode for target operation
drivers/spi/spi-imx.c | 625 +++++++++++++++++++++++++++++++++++-------
1 file changed, 519 insertions(+), 106 deletions(-)
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2.34.1