[RFC PATCH 2/5] dmaengine: allow sun6i-dma for more SoCs

Hi,

On 24/11/16 09:30, Chen-Yu Tsai wrote:

On Thu, Nov 24, 2016 at 5:16 PM, Andre Przywara [off-list ref] wrote:

quoted

Hi,

On 24/11/16 04:16, Chen-Yu Tsai wrote:

quoted

Hi,

On Thu, Nov 24, 2016 at 9:17 AM, Andre Przywara [off-list ref] wrote:

quoted

The sun6i DMA driver is used in the Allwinner A64 and H5 SoC, which
have arm64 capable cores. Add the generic sunxi config symbol to allow
the driver to be selected by arm64 Kconfigs, which don't feature
SoC specific MACH_xxxx configs.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 drivers/dma/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index af63a6b..003c284 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig

@@ -157,7 +157,7 @@ config DMA_SUN4I

 config DMA_SUN6I
        tristate "Allwinner A31 SoCs DMA support"
-       depends on MACH_SUN6I || MACH_SUN8I || COMPILE_TEST
+       depends on MACH_SUN6I || MACH_SUN8I || COMPILE_TEST || ARCH_SUNXI

AFAIK ARCH_SUNXI encompasses/supersedes MACH_SUN*I.
(And I don't have to add MACH_SUN9I later :) )

Sure, admittedly it was just a quick hack to get things going.
Actually I don't know why we had a *depend* on those MACH_s before. I
think technically it does not depend on a certain SoC (having the
COMPILE_TEST in there hints on that). So what about:

It was really because this DMA engine only comes with the later
SoCs. We have dma-sun4i for the older one. But yes, there's no
reason why you can't build it for the earlier SoC. It just doesn't
get used.

quoted

        depends on ARCH_SUNXI || COMPILE_TEST

and maybe:

        default y if MACH_SUN6I || MACH_SUN8I

Though I see that both multi_v7_defconfig and sunxi_defconfig explicitly
set this, so this wouldn't be needed?

I guess it's just nice to get stuff out of defconfig?
Why not go all the way and just have

        default y if ARCH_SUNXI

Well, I am all for it, but I had the impression that there is a lot of
opposition against this approach. Apparently people still want to save
some bytes by building a kernel tailored to one particular SoC.
So I didn't dare to come up with this one.
But it should work to use "# DMA_SUN6I is not selected" in a particular
.config or defconfig to deselect it, right?

Waiting for Maxime's opinion here.

(And also need to check whether the DMA really works on ARM64.
Surprisingly the code compiled cleanly, but I am wondering whether it
properly deals with 32-bit limitation of this controller. I just needed
it because the H3 DT references DMA for SPI and UART).

Cheers,
Andre.