On Fri, May 29, 2020 at 05:40:52PM +0300, Serge Semin wrote: > According to the DW APB DMAC data book the minimum burst transaction > length is 1 and it's true for any version of the controller since > isn't parametrised in the coreAssembler so can't be changed at the > IP-core synthesis stage. The maximum burst transaction can vary from > channel to channel and from controller to controller depending on a > IP-core parameter the system engineer activated during the IP-core > synthesis. Let's initialise both min_burst and max_burst members of the > DMA controller descriptor with extreme values so the DMA clients could > use them to properly optimize the DMA requests. The channels and > controller-specific max_burst length initialization will be introduced > by the follow-up patches. Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> > Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx> > Cc: Alexey Malahov <Alexey.Malahov@xxxxxxxxxxxxxxxxxxxx> > Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx> > Cc: Arnd Bergmann <arnd@xxxxxxxx> > Cc: Rob Herring <robh+dt@xxxxxxxxxx> > Cc: linux-mips@xxxxxxxxxxxxxxx > Cc: devicetree@xxxxxxxxxxxxxxx > > --- > > Changelog v4: > - This is a new patch suggested by Andy. > > Changelog v5: > - Introduce macro with extreme min and max burst length supported by the > DW DMA controller. > - Initialize max_burst length capability with extreme burst length supported > by the DW DMAC IP-core. > --- > drivers/dma/dw/core.c | 2 ++ > include/linux/platform_data/dma-dw.h | 2 ++ > 2 files changed, 4 insertions(+) > > diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c > index ceded21537e2..4887aa2fc73c 100644 > --- a/drivers/dma/dw/core.c > +++ b/drivers/dma/dw/core.c > @@ -1229,6 +1229,8 @@ int do_dma_probe(struct dw_dma_chip *chip) > dw->dma.device_issue_pending = dwc_issue_pending; > > /* DMA capabilities */ > + dw->dma.min_burst = DW_DMA_MIN_BURST; > + dw->dma.max_burst = DW_DMA_MAX_BURST; > dw->dma.src_addr_widths = DW_DMA_BUSWIDTHS; > dw->dma.dst_addr_widths = DW_DMA_BUSWIDTHS; > dw->dma.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV) | > diff --git a/include/linux/platform_data/dma-dw.h b/include/linux/platform_data/dma-dw.h > index f3eaf9ec00a1..369e41e9dcc9 100644 > --- a/include/linux/platform_data/dma-dw.h > +++ b/include/linux/platform_data/dma-dw.h > @@ -12,6 +12,8 @@ > > #define DW_DMA_MAX_NR_MASTERS 4 > #define DW_DMA_MAX_NR_CHANNELS 8 > +#define DW_DMA_MIN_BURST 1 > +#define DW_DMA_MAX_BURST 256 > > /** > * struct dw_dma_slave - Controller-specific information about a slave > -- > 2.26.2 > -- With Best Regards, Andy Shevchenko
