| From | Arnd Bergmann <> | Subject | Re: [PATCH 24/32 v2] dmaengine: ste_dma40: Supply full Device Tree parsing support | Date | Thu, 18 Apr 2013 14:32:11 +0200 |
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On Thursday 18 April 2013, Lee Jones wrote: > +Clients > +Required properties: > +- dmas: Comma separated list of dma channel requests > +- dma-names: Names of the aforementioned requested channels > + > +Each dmas request consists of 4 cells: > + 1. A phandle pointing to the DMA controller > + 2. Device Type > + 3. The DMA request line number (only when 'use fixed channel' is set) > + 4. A 32bit mask specifying; mode, direction and endianess [NB: This list will grow] > + bit 1: Mode: > + 0: Logical > + 1: Physical > + bit 2: Direction: > + 0: Mem to Mem > + 1: Mem to Dev
You probably mean
0: Dev to mem
Related to this, I would recommend not listing bit numbers like this, since there is some amount of confusion regarding how they are counted: zero-based on one-based and LSB-to-MSB or MSB-to-LSB
You can completely avoid this problem by listing them as bit masks:
0x00000002: Logical channel when unset Physical channel when set 0x00000004: Direction from device when unset Direction to device when unset ...
> + dmas = <&dma 13 0 0x8>, /* Logical - DevToMem */ > + <&dma 13 0 0x4>; /* Logical - MemToDev */
The bit in the example no longer matches the description.
> + > + switch (D40_DT_FLAGS_DIR(flags)) { > + case 0: cfg.dir = STEDMA40_MEM_TO_MEM; break; > + case 1: cfg.dir = STEDMA40_MEM_TO_PERIPH; break; > + }
Same typo above.
> + if (cfg.dir == STEDMA40_PERIPH_TO_MEM) > + cfg.src_info.big_endian = D40_DT_FLAGS_BIG_ENDIAN(flags); > + if (cfg.dir == STEDMA40_MEM_TO_PERIPH) > + cfg.dst_info.big_endian = D40_DT_FLAGS_BIG_ENDIAN(flags);
You can fold these two into the switch statement above.
Arnd
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