Hi Vinod On 10/07/2018 04:57 PM, Vinod wrote: > On 28-09-18, 15:01, Pierre-Yves MORDRET wrote: >> From: M'boumba Cedric Madianga <[email protected]> >> >> This patch adds dma bindings to support DMA/MDMA chaining transfer. >> 1 bit is to manage both DMA FIFO Threshold >> 1 bit is to manage DMA/MDMA Chaining features. >> 2 bits are used to specify SDRAM size to use for DMA/MDMA chaining. > > Please do mention which specific bits?
This is written below into DMA Client section. But I can put some words here. > >> The size in bytes of a certain order is given by the formula: >> (2 ^ order) * PAGE_SIZE. >> The order is given by those 2 bits. >> For cyclic, whether chaining is chosen, any value above 1 can be set : >> SRAM buffer size will rely on period size and not on this DT value. >> >> Signed-off-by: Pierre-Yves MORDRET <[email protected]> >> --- >> Version history: >> v3: >> v2: >> * rework content >> v1: >> * Initial >> --- >> --- >> .../devicetree/bindings/dma/stm32-dma.txt | 27 >> +++++++++++++++++++++- >> 1 file changed, 26 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/devicetree/bindings/dma/stm32-dma.txt >> b/Documentation/devicetree/bindings/dma/stm32-dma.txt >> index c5f5190..2bac8c7 100644 >> --- a/Documentation/devicetree/bindings/dma/stm32-dma.txt >> +++ b/Documentation/devicetree/bindings/dma/stm32-dma.txt >> @@ -17,6 +17,12 @@ Optional properties: >> - resets: Reference to a reset controller asserting the DMA controller >> - st,mem2mem: boolean; if defined, it indicates that the controller supports >> memory-to-memory transfer >> +- dmas: A list of eight dma specifiers, one for each entry in dma-names. >> + Refer to stm32-mdma.txt for more details. >> +- dma-names: should contain "ch0", "ch1", "ch2", "ch3", "ch4", "ch5", "ch6" >> and >> + "ch7" and represents each STM32 DMA channel connected to a STM32 MDMA one. >> +- memory-region : phandle to a node describing memory to be used for >> + M2M intermediate transfer between DMA and MDMA. >> >> Example: >> >> @@ -36,6 +42,16 @@ Example: >> st,mem2mem; >> resets = <&rcc 150>; >> dma-requests = <8>; >> + dmas = <&mdma1 8 0x10 0x1200000a 0x40026408 0x00000020 1>, >> + <&mdma1 9 0x10 0x1200000a 0x40026408 0x00000800 1>, >> + <&mdma1 10 0x10 0x1200000a 0x40026408 0x00200000 1>, >> + <&mdma1 11 0x10 0x1200000a 0x40026408 0x08000000 1>, >> + <&mdma1 12 0x10 0x1200000a 0x4002640C 0x00000020 1>, >> + <&mdma1 13 0x10 0x1200000a 0x4002640C 0x00000800 1>, >> + <&mdma1 14 0x10 0x1200000a 0x4002640C 0x00200000 1>, >> + <&mdma1 15 0x10 0x1200000a 0x4002640C 0x08000000 1>; >> + dma-names = "ch0", "ch1", "ch2", "ch3", "ch4", "ch5", "ch6", >> "ch7"; >> + memory-region = <&sram_dmapool>; >> }; >> >> * DMA client >> @@ -68,7 +84,16 @@ channel: a phandle to the DMA controller plus the >> following four integer cells: >> 0x1: 1/2 full FIFO >> 0x2: 3/4 full FIFO >> 0x3: full FIFO >> - >> + -bit 2: Intermediate M2M transfer from/to DDR to/from SRAM throughout MDMA >> + 0: MDMA not used to generate an intermediate M2M transfer >> + 1: MDMA used to generate an intermediate M2M transfer. >> + -bit 3-4: indicated SRAM Buffer size in (2^order)*PAGE_SIZE. >> + PAGE_SIZE is given by Linux at 4KiB: include/asm-generic/page.h. >> + Order is given by those 2 bits starting at 0. >> + Valid only whether Intermediate M2M transfer is set. > > why do we need this as a property? In some UC, we need more than 4KiB in case of chaining for better performances. Chaining has to be enabled by client if performance is at sacks. > >> + For cyclic, whether Intermediate M2M transfer is chosen, any value can >> + be set: SRAM buffer size will rely on period size and not on this DT >> + value. >> >> Example: >> >> -- >> 2.7.4 >
