[PATCH 01/30] usb: dwc2: Deprecate g-use-dma binding

[robh@kernel.org (Rob Herring)]

On Tue, Nov 08, 2016 at 09:48:03AM -0800, John Youn wrote:
> On 11/8/2016 1:12 AM, Felipe Balbi wrote:
> > 
> > Hi,
> > 
> > John Youn <johnyoun@synopsys.com> writes:
> >> Add a vendor prefix and make the name more consistent by renaming it to
> >> "snps,gadget-dma-enable".
> >>
> >> Signed-off-by: John Youn <johnyoun@synopsys.com>
> >> ---
> >>  Documentation/devicetree/bindings/usb/dwc2.txt | 5 ++++-
> >>  arch/arm/boot/dts/rk3036.dtsi                  | 2 +-
> >>  arch/arm/boot/dts/rk3288.dtsi                  | 2 +-
> >>  arch/arm/boot/dts/rk3xxx.dtsi                  | 2 +-
> >>  arch/arm64/boot/dts/hisilicon/hi6220.dtsi      | 2 +-
> >>  arch/arm64/boot/dts/rockchip/rk3368.dtsi       | 2 +-
> >>  drivers/usb/dwc2/params.c                      | 9 ++++++++-
> >>  drivers/usb/dwc2/pci.c                         | 2 +-
> >>  8 files changed, 18 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/usb/dwc2.txt b/Documentation/devicetree/bindings/usb/dwc2.txt
> >> index 9472111..389a461 100644
> >> --- a/Documentation/devicetree/bindings/usb/dwc2.txt
> >> +++ b/Documentation/devicetree/bindings/usb/dwc2.txt
> >> @@ -26,11 +26,14 @@ Refer to phy/phy-bindings.txt for generic phy consumer properties
> >>  - dr_mode: shall be one of "host", "peripheral" and "otg"
> >>    Refer to usb/generic.txt
> >>  - snps,host-dma-disable: disable host DMA mode.
> >> -- g-use-dma: enable dma usage in gadget driver.
> >> +- snps,gadget-dma-enable: enable gadget DMA mode.
> > 
> > I don't see why you even have this binding. Looking through the code,
> > you have:
> > 
> > #define GHWCFG2_SLAVE_ONLY_ARCH			0
> > #define GHWCFG2_EXT_DMA_ARCH			1
> > #define GHWCFG2_INT_DMA_ARCH			2
> > 
> > void dwc2_set_param_dma_enable(struct dwc2_hsotg *hsotg, int val)
> > {
> > 	int valid = 1;
> > 
> > 	if (val > 0 && hsotg->hw_params.arch == GHWCFG2_SLAVE_ONLY_ARCH)
> > 		valid = 0;
> > 	if (val < 0)
> > 		valid = 0;
> > 
> > 	if (!valid) {
> > 		if (val >= 0)
> > 			dev_err(hsotg->dev,
> > 				"%d invalid for dma_enable parameter. Check HW configuration.\n",
> > 				val);
> > 		val = hsotg->hw_params.arch != GHWCFG2_SLAVE_ONLY_ARCH;
> > 		dev_dbg(hsotg->dev, "Setting dma_enable to %d\n", val);
> > 	}
> > 
> > 	hsotg->core_params->dma_enable = val;
> > }
> > 
> > which seems to hint that DMA support is discoverable. If there is DMA,
> > why would disable it?
> > 
> 
> Yes that's the case and I would prefer to make it discoverable and
> enabled by default.
> 
> But the legacy behavior has always been like this because DMA was
> never fully implemented in the gadget driver and it was an opt-in
> feature. Periodic support was only added recently.
> 
> What do you think about enabling it by default now? I think most
> platforms already use DMA.
> 
> We would still need a "disable" binding for IP validation purposes at
> least.

You can hack up your kernel for that. You may need a disable for broken 
h/w perhaps.

Rob