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| author | Serge Semin <Sergey.Semin@baikalelectronics.ru> | 2020-07-23 03:58:48 +0300 |
|---|---|---|
| committer | Vinod Koul <vkoul@kernel.org> | 2020-07-27 14:30:55 +0530 |
| commit | 0f9d5f008e2f096b14ff1f218a870199dd5264f4 (patch) | |
| tree | f7e329024760c273097ef5eccc74c0cb1c4d7faa /drivers/dma | |
| parent | ca7f2851712e7072e8f327882dc4bdaaae3a8079 (diff) | |
| download | linux-stable-0f9d5f008e2f096b14ff1f218a870199dd5264f4.tar.gz linux-stable-0f9d5f008e2f096b14ff1f218a870199dd5264f4.tar.bz2 linux-stable-0f9d5f008e2f096b14ff1f218a870199dd5264f4.zip | |
dmaengine: dw: Initialize max_sg_burst capability
Multi-block support provides a way to map the kernel-specific SG-table so
the DW DMA device would handle it as a whole instead of handling the
SG-list items or so called LLP block items one by one. So if true LLP
list isn't supported by the DW DMA engine, then soft-LLP mode will be
utilized to load and execute each LLP-block one by one. The soft-LLP mode
of the DMA transactions execution might not work well for some DMA
consumers like SPI due to its Tx and Rx buffers inter-dependency. Let's
initialize the max_sg_burst DMA channels capability based on the nollp
flag state. If it's true, no hardware accelerated LLP is available and
max_sg_burst should be set with 1, which means that the DMA engine
can handle only a single SG list entry at a time. If noLLP is set to
false, then hardware accelerated LLP is supported and the DMA engine
can handle infinite number of SG entries in a single DMA transaction.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200723005848.31907-11-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Diffstat (limited to 'drivers/dma')
| -rw-r--r-- | drivers/dma/dw/core.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c index 588b9bae827c..eb9175133034 100644 --- a/drivers/dma/dw/core.c +++ b/drivers/dma/dw/core.c @@ -1059,6 +1059,18 @@ static void dwc_caps(struct dma_chan *chan, struct dma_slave_caps *caps) struct dw_dma_chan *dwc = to_dw_dma_chan(chan); caps->max_burst = dwc->max_burst; + + /* + * It might be crucial for some devices to have the hardware + * accelerated multi-block transfers supported, aka LLPs in DW DMAC + * notation. So if LLPs are supported then max_sg_burst is set to + * zero which means unlimited number of SG entries can be handled in a + * single DMA transaction, otherwise it's just one SG entry. + */ + if (dwc->nollp) + caps->max_sg_burst = 1; + else + caps->max_sg_burst = 0; } int do_dma_probe(struct dw_dma_chip *chip) |