[PATCHv2 1/2] usb: dwc2: Disable descriptor dma mode by default

[PATCHv2 1/2] usb: dwc2: Disable descriptor dma mode by default

[dinguyen-EIB2kfCEclfQT0dZR+AlfA]

From: Dinh Nguyen <dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org>

Even though the IP supports Descriptor DMA mode, it does not support SPLIT
transactions in this mode. So the driver, in its currently form, will not
support LS/FS devices when connected to a HS Hub if Descriptor DMA mode is
enabled.

So we disable descriptor dma mode by default and a provide device tree property
for users to enable it if they really want to.

Signed-off-by: Dinh Nguyen <dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org>
---
v2:
- Reworked patch to disable descriptor dma by default
- Removed unneeded helper variable
- Reword patch commit header
---
 drivers/usb/dwc2/platform.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/usb/dwc2/platform.c b/drivers/usb/dwc2/platform.c
index eaba547..cc50d00 100644
--- a/drivers/usb/dwc2/platform.c
+++ b/drivers/usb/dwc2/platform.c
@@ -134,6 +134,16 @@ static int dwc2_driver_probe(struct platform_device *dev)
 		/* Default all params to autodetect */
 		dwc2_set_all_params(&defparams, -1);
 		params = &defparams;
+
+		/*
+		 * Disable descriptor dma mode by default as the HW can support
+		 * it, but does not support it for SPLIT transactions. One can
+		 * use the device tree property "dma-desc-enable", if one really
+		 * wants to enable descriptor dma mode.
+		 */
+		defparams.dma_desc_enable = 0;
+		of_property_read_u32(dev->dev.of_node, "dma-desc-enable",
+					&defparams.dma_desc_enable);
 	}
 
 	hsotg = devm_kzalloc(&dev->dev, sizeof(*hsotg), GFP_KERNEL);
-- 
1.7.9.5

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[PATCHv2 2/2] Documentation: dt: add an optional dma-desc-enable property for dwc2 usb

[dinguyen-EIB2kfCEclfQT0dZR+AlfA]

From: Dinh Nguyen <dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org>

The "dma-desc-enable" property can be used to enable descriptor DMA mode
for the DWC2 USB IP.

Signed-off-by: Dinh Nguyen <dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org>
---
v2: Reword property description to enable instead of disable
---
 Documentation/devicetree/bindings/usb/dwc2.txt |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/usb/dwc2.txt b/Documentation/devicetree/bindings/usb/dwc2.txt
index b8b6871..9b471b5 100644
--- a/Documentation/devicetree/bindings/usb/dwc2.txt
+++ b/Documentation/devicetree/bindings/usb/dwc2.txt
@@ -14,6 +14,13 @@ Refer to clk/clock-bindings.txt for generic clock consumer properties
 Optional properties:
 - phys: phy provider specifier
 - phy-names: shall be "device"
+- dma-desc-enable: Should be <1> to enable descriptor dma mode. This
+	property is used to enable descriptor DMA support. The reason why
+	this property is needed is because the HW supports descriptor DMA
+	mode, but descriptor dma mode will not support SPLIT transactions.
+	So this property can be used to optionally enable descriptor DMA
+	support.
+
 Refer to phy/phy-bindings.txt for generic phy consumer properties
 
 Example:
-- 
1.7.9.5

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Re: [PATCHv2 2/2] Documentation: dt: add an optional dma-desc-enable property for dwc2 usb

[Sergei Shtylyov]

Hello.

On 07-05-2014 3:00, dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org wrote:

> From: Dinh Nguyen <dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org>

> The "dma-desc-enable" property can be used to enable descriptor DMA mode
> for the DWC2 USB IP.

> Signed-off-by: Dinh Nguyen <dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org>
> ---
> v2: Reword property description to enable instead of disable
> ---
>   Documentation/devicetree/bindings/usb/dwc2.txt |    7 +++++++
>   1 file changed, 7 insertions(+)

> diff --git a/Documentation/devicetree/bindings/usb/dwc2.txt b/Documentation/devicetree/bindings/usb/dwc2.txt
> index b8b6871..9b471b5 100644
> --- a/Documentation/devicetree/bindings/usb/dwc2.txt
> +++ b/Documentation/devicetree/bindings/usb/dwc2.txt
> @@ -14,6 +14,13 @@ Refer to clk/clock-bindings.txt for generic clock consumer properties
>   Optional properties:
>   - phys: phy provider specifier
>   - phy-names: shall be "device"
> +- dma-desc-enable: Should be <1> to enable descriptor dma mode. This
> +	property is used to enable descriptor DMA support. The reason why
> +	this property is needed is because the HW supports descriptor DMA
> +	mode, but descriptor dma mode will not support SPLIT transactions.
> +	So this property can be used to optionally enable descriptor DMA
> +	support.

    Why not make this property boolean?

WBR, Sergei

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RE: [PATCHv2 1/2] usb: dwc2: Disable descriptor dma mode by default

[Paul Zimmerman]

> From: dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org [mailto:dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org]
> Sent: Tuesday, May 06, 2014 4:01 PM
> 
> Even though the IP supports Descriptor DMA mode, it does not support SPLIT
> transactions in this mode. So the driver, in its currently form, will not
> support LS/FS devices when connected to a HS Hub if Descriptor DMA mode is
> enabled.
> 
> So we disable descriptor dma mode by default and a provide device tree property
> for users to enable it if they really want to.

Hi Dinh,

I'd prefer not to add the DT property, at least for now. I doubt if
anyone will want to enable it. Besides, I'm not sure that a property
which only enables a driver feature is appropriate for DT.

So, if you redo patch 1 to remove the DT property read, and drop patch
2, you can add my acked-by. Thanks.

-- 
Paul

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