On Thu, Jan 25, 2024 at 11:09 PM Andre Przywara <andre.przywara@xxxxxxx> wrote: > > On Thu, 25 Jan 2024 22:37:34 +0800 > Chen-Yu Tsai <wens@xxxxxxxxxx> wrote: > > Hi, > > > On Tue, Jan 23, 2024 at 8:41 AM Andre Przywara <andre.przywara@xxxxxxx> wrote: > > > > > > On Tue, 23 Jan 2024 01:05:15 +0800 > > > Chen-Yu Tsai <wens@xxxxxxxxxx> wrote: > > > > > > Hi, > > > > > > > From: Chen-Yu Tsai <wens@xxxxxxxx> > > > > > > > > The DMA controllers found on the H616 and H618 are the same as the one > > > > found on the H6. The only difference is the DMA endpoint (DRQ) layout. > > > > > > That does not seem to be entirely true: The H616 encodes the two lowest > > > bits in DMA_DESC_ADDR_REG differently: on the H6 they must be 0 (word > > > aligned), on the H616 these contain bits [33:32] of the address of the > > > DMA descriptor. The manual doesn't describe the descriptor format in > > > much detail, but ec31c5c59492 suggests that those two bits are put in > > > the "para" word of the descriptor. > > > > Good catch. So, same as the A100 I believe? > > Yes, that's what I got as well. > > > > The good thing it that this encoding is backwards compatible, so I > > > think the fallback string still holds: Any driver just implementing the > > > H6 encoding would be able to drive the H616. > > > > > > I think the A100 was mis-described, as mentioned here: > > > https://lore.kernel.org/linux-arm-kernel/29e575b6-14cb-73f1-512d-9f0f934490ea@xxxxxxx/ > > > I think we should: > > > - make the A100 use: "allwinner,sun50i-a100-dma", "sun50i-h6-dma" > > > - make the H616 use: "allwinner,sun50i-h616-dma", "allwinner,sun50i-a100-dma", "sun50i-h6-dma" > > > > > > Does that make sense? > > > > I wouldn't call that exactly backward compatible. Say the driver forgot to > > clear the two bits. It would work fine on the H6, but the accessed address > > could be way off on the A100 and H616. > > I don't know the exact boundaries of "compatible" here, but the H6 manual > pretty clearly states "The descriptor address must be word-aligned." > But since the A100 compatible is known and supported for a while, that > doesn't really matter, practically speaking, I guess. I'd say that makes the descriptor address register backward compatible, > One could check how the H6 DMA controller reacts to those bits not being > 0, not sure if I find the time, though. but no idea about the parameter field in the descriptor. So for now I think we should just be cautious. Since as you mentioned the A100 is already supported and listed separately, lets just keep that for now. ChenYu [...]
