On Mon, Jun 17, 2024 at 5:48 PM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote: > > On 17/06/2024 16:04, Piotr Wojtaszczyk wrote: > >> > >>> It's used by snd_soc_dai_init_dma_data() in [PATCH v3 4/4] to give the > >>> dmaengine a > >>> hint which dma config to use. The LPC32xx doesn't have yet a dmamux driver like > >> > >> and if I change driver platform data to foo and bar, does the DTS work? No. > > > > They shouldn't change the same way as expected dma-names shouldn't change. > > Lots of drivers expect the dma-names to be "rx", "tx" > > > >> > >>> lpc18xx-dmamux.c therefore it still uses platform data entries for > >>> pl08x dma channels > >>> and 'SND_DMAENGINE_PCM_FLAG_NO_DT | SND_DMAENGINE_PCM_FLAG_COMPAT' > >>> flags in the devm_snd_dmaengine_pcm_register(). > >>> Typically instead of this platform data you would use regular 'dma' > >>> and 'dma-names' if it had > >>> proper dmamux driver like lpc18xx-dmamux.c > >> > >> Exactly. Use these. > > > > Then I need to write a lpc32xx dma mux driver, device tree binding for > > it and adjust the > > LPC32xx I2S driver for it. Is this a hard requirement to accept this > > patch set for the > > legacy LPC32xx SoC? > > I do not see at all analogy with dma-names. dma-names are used ONLY by > the consumer to pick up proper property "dmas" from DT. They are not > passed to DMA code. They are not used to configure DMA provider at all. > > You parse string from DT and pass it further as DMA filtering code. This > is abuse of hardware description for programming your driver and their > dependencies. > > Why you cannot hard-code them? > > Sorry, to be clear: NAK That's fine, clear answers are always good. I considered to hardcode this as it was in the first version of the patch set but LPC32XX has two I2S interfaces which use different DMA signals and mux settings and I really didn't want to pick the virtual DMA channel name based on hardcoded I2S node name therefore I thought having a DT property to select proper dma channel is a better solution. -- Piotr Wojtaszczyk Timesys
