Hi Jernej, On 6/20/22 1:28 PM, Jernej Škrabec wrote: > Dne petek, 17. junij 2022 ob 05:42:09 CEST je Samuel Holland napisal(a): >> The sun6i DMA engine supports segment sizes up to 2^25-1 bytes. This is >> explicitly stated in newer SoC documentation (H6, D1), and it is implied >> in older documentation by the 25-bit width of the "bytes left in the >> current segment" register field. > > At least A10 user manual says 128k max in description for Byte Counter > register (0x100+N*0x20+0xC), although field size is defined as 23:0, but that's > still less than 2^25-1. A20 supports only 128k too according to manual. New > quirk should be introduced for this. Thanks for checking this. A10 and A20 use a separate driver (sun4i-dma). That driver will also benefit from setting the max segment size, so I will send a patch for it. I think all of the variants supported by sun6i-dma have the same segment size capability, so no quirk is needed here. Regards, Samuel >> >> Exposing the real segment size limit (instead of the 64k default) >> reduces the number of SG list segments needed for a transaction. >> >> Signed-off-by: Samuel Holland <samuel@xxxxxxxxxxxx> >> --- >> Tested on A64, verified that the maximum ALSA PCM period increased, and >> that audio playback still worked. >> >> drivers/dma/sun6i-dma.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c >> index b7557f437936..1425f87d97b7 100644 >> --- a/drivers/dma/sun6i-dma.c >> +++ b/drivers/dma/sun6i-dma.c >> @@ -9,6 +9,7 @@ >> >> #include <linux/clk.h> >> #include <linux/delay.h> >> +#include <linux/dma-mapping.h> >> #include <linux/dmaengine.h> >> #include <linux/dmapool.h> >> #include <linux/interrupt.h> >> @@ -1334,6 +1335,8 @@ static int sun6i_dma_probe(struct platform_device > *pdev) >> INIT_LIST_HEAD(&sdc->pending); >> spin_lock_init(&sdc->lock); >> >> + dma_set_max_seg_size(&pdev->dev, DMA_BIT_MASK(25)); >> + >> dma_cap_set(DMA_PRIVATE, sdc->slave.cap_mask); >> dma_cap_set(DMA_MEMCPY, sdc->slave.cap_mask); >> dma_cap_set(DMA_SLAVE, sdc->slave.cap_mask); >> -- >> 2.35.1 >> >> > >
