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. One could check how the H6 DMA controller reacts to those bits not being 0, not sure if I find the time, though. Cheers, Andre. > > Cheers, > > Andre > > > > > Since the number of channels and endpoints are described with additional > > > generic properties, just add a new H616-specific compatible string and > > > fallback to the H6 one. > > > > > > Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxx> > > > --- > > > .../bindings/dma/allwinner,sun50i-a64-dma.yaml | 15 +++++++++++---- > > > 1 file changed, 11 insertions(+), 4 deletions(-) > > > > > > diff --git a/Documentation/devicetree/bindings/dma/allwinner,sun50i-a64-dma.yaml b/Documentation/devicetree/bindings/dma/allwinner,sun50i-a64-dma.yaml > > > index ec2d7a789ffe..e5693be378bd 100644 > > > --- a/Documentation/devicetree/bindings/dma/allwinner,sun50i-a64-dma.yaml > > > +++ b/Documentation/devicetree/bindings/dma/allwinner,sun50i-a64-dma.yaml > > > @@ -28,6 +28,9 @@ properties: > > > - items: > > > - const: allwinner,sun8i-r40-dma > > > - const: allwinner,sun50i-a64-dma > > > + - items: > > > + - const: allwinner,sun50i-h616-dma > > > + - const: allwinner,sun50i-h6-dma > > > > > > reg: > > > maxItems: 1 > > > @@ -59,10 +62,14 @@ required: > > > if: > > > properties: > > > compatible: > > > - enum: > > > - - allwinner,sun20i-d1-dma > > > - - allwinner,sun50i-a100-dma > > > - - allwinner,sun50i-h6-dma > > > + oneOf: > > > + - enum: > > > + - allwinner,sun20i-d1-dma > > > + - allwinner,sun50i-a100-dma > > > + - allwinner,sun50i-h6-dma > > > + - items: > > > + - const: allwinner,sun50i-h616-dma > > > + - const: allwinner,sun50i-h6-dma > > > > > > then: > > > properties: > > >
