[PATCH] ARM: davinci: Add the clock for the CPPI 4.1 DMA engine

[Sekhar Nori]

On Wednesday 29 March 2017 09:39 PM, Alexandre Bailon wrote:
> The CPPI 4.1 DMA is sharing its clock with the USB OTG,
> and most of the time, the clock will be enabled by USB.
> But during the init of the DMA, USB is not enabled (waiting for DMA),
> and then we must enable the clock before to do anything.
> Add the clock for the CPPI 4.1 DMA engine.
> 
> Note:
> This patch is to apply instead of:
> "ARM: davinci: Make the usb20 clock available to PM runtime"

Okay, but I still liked the fact that that patch was using NULL as
con_id for MUSB clock. That makes sense because MUSB gets a single clock
input. I think you should still make that change. If not for v4.12, then
for v4.13.

> 
> Signed-off-by: Alexandre Bailon <abailon at baylibre.com>
> ---
>  arch/arm/mach-davinci/da830.c    | 1 +
>  arch/arm/mach-davinci/da850.c    | 1 +
>  arch/arm/mach-davinci/da8xx-dt.c | 2 ++
>  3 files changed, 4 insertions(+)
> 
> diff --git a/arch/arm/mach-davinci/da830.c b/arch/arm/mach-davinci/da830.c
> index 073c458..ae4a8a5 100644
> --- a/arch/arm/mach-davinci/da830.c
> +++ b/arch/arm/mach-davinci/da830.c
> @@ -413,6 +413,7 @@ static struct clk_lookup da830_clks[] = {
>  	CLK("davinci-mcasp.1",	NULL,		&mcasp1_clk),
>  	CLK("davinci-mcasp.2",	NULL,		&mcasp2_clk),
>  	CLK("musb-da8xx",	"usb20",	&usb20_clk),
> +	CLK("cppi41-dmaengine",	NULL,		&usb20_clk),

Did you try reading /sys/kernel/debug/davinci_clocks after this patch?
It will hang because of the loop created here.

Looks like what you want is cppi4.1 dma clock to be a child of MUSB
clock. That way, even if DMA is enabled before MUSB, it still works.

Thanks,
Sekhar