[PATCH V1 0/4] Tegra XUDC support on Tegra194 Soc

[PATCH V1 0/4] Tegra XUDC support on Tegra194 Soc

[Nagarjuna Kristam]

This patch series adds support for XUSB Device Mode support on Tegra194 SoCs.

This patchset is composed with:
 - dt bindings of XUDC driver.
 - dt changes to add xudc node on Tegra194 Soc.
 - USB driver changes to tegra-xudc to add support on Tegra194 Soc. 

Nagarjuna Kristam (4):
  dt-bindings: usb: tegra-xudc: Add Tegra194 XUSB controller support
  arm64: tegra: Add xudc node for Tegra194
  usb: gadget: tegra-xudc: Add Tegra194 support
  usb: gadget: tegra-xudc: add port_speed_quirk

 .../devicetree/bindings/usb/nvidia,tegra-xudc.yaml |   2 +
 arch/arm64/boot/dts/nvidia/tegra194.dtsi           |  18 +++
 drivers/usb/gadget/udc/tegra-xudc.c                | 130 +++++++++++++++++++++
 3 files changed, 150 insertions(+)

-- 
2.7.4

[PATCH V1 1/4] dt-bindings: usb: tegra-xudc: Add Tegra194 XUSB controller support

[Nagarjuna Kristam]

Extend the Tegra XUSB controller device tree binding with Tegra194
support.

Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
---
 Documentation/devicetree/bindings/usb/nvidia,tegra-xudc.yaml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/usb/nvidia,tegra-xudc.yaml b/Documentation/devicetree/bindings/usb/nvidia,tegra-xudc.yaml
index b84ed8e..75ea946 100644
--- a/Documentation/devicetree/bindings/usb/nvidia,tegra-xudc.yaml
+++ b/Documentation/devicetree/bindings/usb/nvidia,tegra-xudc.yaml
@@ -21,6 +21,7 @@ properties:
       - enum:
           - nvidia,tegra210-xudc # For Tegra210
           - nvidia,tegra186-xudc # For Tegra186
+          - nvidia,tegra194-xudc # For Tegra194
 
   reg:
     minItems: 2
@@ -144,6 +145,7 @@ allOf:
           contains:
             enum:
               - nvidia,tegra186-xudc
+              - nvidia,tegra194-xudc
     then:
       properties:
         reg:
-- 
2.7.4

Re: [PATCH V1 1/4] dt-bindings: usb: tegra-xudc: Add Tegra194 XUSB controller support

[Thierry Reding]

[-- Attachment #1: Type: text/plain, Size: 376 bytes --]

On Thu, Apr 16, 2020 at 01:04:17PM +0530, Nagarjuna Kristam wrote:
> Extend the Tegra XUSB controller device tree binding with Tegra194
> support.
> 
> Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
> ---
>  Documentation/devicetree/bindings/usb/nvidia,tegra-xudc.yaml | 2 ++
>  1 file changed, 2 insertions(+)

Acked-by: Thierry Reding <treding@nvidia.com>

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH V1 1/4] dt-bindings: usb: tegra-xudc: Add Tegra194 XUSB controller support

[Rob Herring]

On Thu, 16 Apr 2020 13:04:17 +0530, Nagarjuna Kristam wrote:
> Extend the Tegra XUSB controller device tree binding with Tegra194
> support.
> 
> Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
> ---
>  Documentation/devicetree/bindings/usb/nvidia,tegra-xudc.yaml | 2 ++
>  1 file changed, 2 insertions(+)
> 

Acked-by: Rob Herring <robh@kernel.org>

[PATCH V1 2/4] arm64: tegra: Add xudc node for Tegra194

[Nagarjuna Kristam]

Tegra194 has one XUSB device mode controller, which can be operated
HS and SS modes. Add DT entry for XUSB device mode controller

Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
---
 arch/arm64/boot/dts/nvidia/tegra194.dtsi | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/arm64/boot/dts/nvidia/tegra194.dtsi b/arch/arm64/boot/dts/nvidia/tegra194.dtsi
index f4ede86..e1ae01c 100644
--- a/arch/arm64/boot/dts/nvidia/tegra194.dtsi
+++ b/arch/arm64/boot/dts/nvidia/tegra194.dtsi
@@ -644,6 +644,24 @@
 			};
 		};
 
+		usb@3550000 {
+			compatible = "nvidia,tegra194-xudc";
+			reg = <0x03550000 0x8000>,
+			      <0x03558000 0x1000>;
+			reg-names = "base", "fpci";
+			interrupts = <GIC_SPI 166 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&bpmp TEGRA194_CLK_XUSB_CORE_DEV>,
+				 <&bpmp TEGRA194_CLK_XUSB_CORE_SS>,
+				 <&bpmp TEGRA194_CLK_XUSB_SS>,
+				 <&bpmp TEGRA194_CLK_XUSB_FS>;
+			clock-names = "dev", "ss", "ss_src", "fs_src";
+			power-domains = <&bpmp TEGRA194_POWER_DOMAIN_XUSBB>,
+					<&bpmp TEGRA194_POWER_DOMAIN_XUSBA>;
+			power-domain-names = "dev", "ss";
+			nvidia,xusb-padctl = <&xusb_padctl>;
+			status = "disabled";
+		};
+
 		usb@3610000 {
 			compatible = "nvidia,tegra194-xusb";
 			reg = <0x03610000 0x40000>,
-- 
2.7.4

Re: [PATCH V1 2/4] arm64: tegra: Add xudc node for Tegra194

[Thierry Reding]

[-- Attachment #1: Type: text/plain, Size: 450 bytes --]

On Thu, Apr 16, 2020 at 01:04:18PM +0530, Nagarjuna Kristam wrote:
> Tegra194 has one XUSB device mode controller, which can be operated
> HS and SS modes. Add DT entry for XUSB device mode controller
> 
> Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
> ---
>  arch/arm64/boot/dts/nvidia/tegra194.dtsi | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)

Looks good to me, I'll pick this up into the Tegra tree.

Thierry

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

[PATCH V1 3/4] usb: gadget: tegra-xudc: Add Tegra194 support

[Nagarjuna Kristam]

This commit adds support for XUSB device mode controller support on
Tegra194 SoC. This is very similar to the existing Tegra186 XUDC, with lpm
support added in addition.

Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
---
 drivers/usb/gadget/udc/tegra-xudc.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/usb/gadget/udc/tegra-xudc.c b/drivers/usb/gadget/udc/tegra-xudc.c
index 52a6add..fb01117 100644
--- a/drivers/usb/gadget/udc/tegra-xudc.c
+++ b/drivers/usb/gadget/udc/tegra-xudc.c
@@ -3494,6 +3494,13 @@ static const char * const tegra186_xudc_clock_names[] = {
 	"fs_src",
 };
 
+static const char * const tegra194_xudc_clock_names[] = {
+	"dev",
+	"ss",
+	"ss_src",
+	"fs_src",
+};
+
 static struct tegra_xudc_soc tegra210_xudc_soc_data = {
 	.supply_names = tegra210_xudc_supply_names,
 	.num_supplies = ARRAY_SIZE(tegra210_xudc_supply_names),
@@ -3522,6 +3529,19 @@ static struct tegra_xudc_soc tegra186_xudc_soc_data = {
 	.has_ipfs = false,
 };
 
+static struct tegra_xudc_soc tegra194_xudc_soc_data = {
+	.clock_names = tegra194_xudc_clock_names,
+	.num_clks = ARRAY_SIZE(tegra194_xudc_clock_names),
+	.num_phys = 4,
+	.u1_enable = true,
+	.u2_enable = true,
+	.lpm_enable = true,
+	.invalid_seq_num = false,
+	.pls_quirk = false,
+	.port_reset_quirk = false,
+	.has_ipfs = false,
+};
+
 static const struct of_device_id tegra_xudc_of_match[] = {
 	{
 		.compatible = "nvidia,tegra210-xudc",
@@ -3531,6 +3551,10 @@ static const struct of_device_id tegra_xudc_of_match[] = {
 		.compatible = "nvidia,tegra186-xudc",
 		.data = &tegra186_xudc_soc_data
 	},
+	{
+		.compatible = "nvidia,tegra194-xudc",
+		.data = &tegra194_xudc_soc_data
+	},
 	{ }
 };
 MODULE_DEVICE_TABLE(of, tegra_xudc_of_match);
-- 
2.7.4

Re: [PATCH V1 3/4] usb: gadget: tegra-xudc: Add Tegra194 support

[Thierry Reding]

[-- Attachment #1: Type: text/plain, Size: 1079 bytes --]

On Thu, Apr 16, 2020 at 01:04:19PM +0530, Nagarjuna Kristam wrote:
> This commit adds support for XUSB device mode controller support on
> Tegra194 SoC. This is very similar to the existing Tegra186 XUDC, with lpm
> support added in addition.
> 
> Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
> ---
>  drivers/usb/gadget/udc/tegra-xudc.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/usb/gadget/udc/tegra-xudc.c b/drivers/usb/gadget/udc/tegra-xudc.c
> index 52a6add..fb01117 100644
> --- a/drivers/usb/gadget/udc/tegra-xudc.c
> +++ b/drivers/usb/gadget/udc/tegra-xudc.c
> @@ -3494,6 +3494,13 @@ static const char * const tegra186_xudc_clock_names[] = {
>  	"fs_src",
>  };
>  
> +static const char * const tegra194_xudc_clock_names[] = {
> +	"dev",
> +	"ss",
> +	"ss_src",
> +	"fs_src",
> +};
> +

This looks identical to tegra186_xudc_clock_names, so there's no need to
duplicate them. Just reuse the other one for Tegra194.

With that fixed:

Acked-by: Thierry Reding <treding@nvidia.com>

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

[PATCH V1 4/4] usb: gadget: tegra-xudc: add port_speed_quirk

[Nagarjuna Kristam]

Add port_speed_quirk that modify below registers to limit/restore OTG
port speed to GEN1/GEN2.
SSPX_CORE_CNT56
SSPX_CORE_CNT57
SSPX_CORE_CNT65
SSPX_CORE_CNT66
SSPX_CORE_CNT67
SSPX_CORE_CNT72

The basic idea is to make SCD intentionally fail, reduce SCD timeout and
force device transit to TSEQ. Enable this flag to only Tegra194.

Based on work by WayneChang <waynec@nvidia.com>

Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
---
 drivers/usb/gadget/udc/tegra-xudc.c | 106 ++++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)

diff --git a/drivers/usb/gadget/udc/tegra-xudc.c b/drivers/usb/gadget/udc/tegra-xudc.c
index fb01117..63484f98 100644
--- a/drivers/usb/gadget/udc/tegra-xudc.c
+++ b/drivers/usb/gadget/udc/tegra-xudc.c
@@ -158,6 +158,30 @@
 #define  SSPX_CORE_CNT32_POLL_TBURST_MAX_MASK GENMASK(7, 0)
 #define  SSPX_CORE_CNT32_POLL_TBURST_MAX(x) ((x) & \
 					SSPX_CORE_CNT32_POLL_TBURST_MAX_MASK)
+#define SSPX_CORE_CNT56 0x6fc
+#define  SSPX_CORE_CNT56_SCD_BIT0_TRPT_MAX_MASK GENMASK(19, 0)
+#define  SSPX_CORE_CNT56_SCD_BIT0_TRPT_MAX(x) ((x) & \
+				SSPX_CORE_CNT56_SCD_BIT0_TRPT_MAX_MASK)
+#define SSPX_CORE_CNT57 0x700
+#define  SSPX_CORE_CNT57_SCD_BIT1_TRPT_MAX_MASK GENMASK(19, 0)
+#define  SSPX_CORE_CNT57_SCD_BIT1_TRPT_MAX(x) ((x) & \
+				SSPX_CORE_CNT57_SCD_BIT1_TRPT_MAX_MASK)
+#define SSPX_CORE_CNT65 0x720
+#define  SSPX_CORE_CNT65_TX_SCD_END_TRPT_MID_MASK GENMASK(19, 0)
+#define  SSPX_CORE_CNT65_TX_SCD_END_TRPT_MID(x) ((x) & \
+				SSPX_CORE_CNT65_TX_SCD_END_TRPT_MID_MASK)
+#define SSPX_CORE_CNT66 0x724
+#define  SSPX_CORE_CNT66_TX_SCD_BIT0_TRPT_MID_MASK GENMASK(19, 0)
+#define  SSPX_CORE_CNT66_TX_SCD_BIT0_TRPT_MID(x) ((x) & \
+				SSPX_CORE_CNT66_TX_SCD_BIT0_TRPT_MID_MASK)
+#define SSPX_CORE_CNT67 0x728
+#define  SSPX_CORE_CNT67_TX_SCD_BIT1_TRPT_MID_MASK GENMASK(19, 0)
+#define  SSPX_CORE_CNT67_TX_SCD_BIT1_TRPT_MID(x) ((x) & \
+				SSPX_CORE_CNT67_TX_SCD_BIT1_TRPT_MID_MASK)
+#define SSPX_CORE_CNT72 0x73c
+#define  SSPX_CORE_CNT72_SCD_LFPS_TIMEOUT_MASK GENMASK(19, 0)
+#define  SSPX_CORE_CNT72_SCD_LFPS_TIMEOUT(x) ((x) & \
+				SSPX_CORE_CNT72_SCD_LFPS_TIMEOUT_MASK)
 #define SSPX_CORE_PADCTL4 0x750
 #define  SSPX_CORE_PADCTL4_RXDAT_VLD_TIMEOUT_U3_MASK GENMASK(19, 0)
 #define  SSPX_CORE_PADCTL4_RXDAT_VLD_TIMEOUT_U3(x) ((x) & \
@@ -530,6 +554,7 @@ struct tegra_xudc_soc {
 	bool invalid_seq_num;
 	bool pls_quirk;
 	bool port_reset_quirk;
+	bool port_speed_quirk;
 	bool has_ipfs;
 };
 
@@ -599,6 +624,78 @@ static inline void dump_trb(struct tegra_xudc *xudc, const char *type,
 		trb->control);
 }
 
+static void tegra_xudc_limit_port_speed(struct tegra_xudc *xudc)
+{
+	u32 val;
+
+	/* limit port speed to gen 1 */
+	val = xudc_readl(xudc, SSPX_CORE_CNT56);
+	val &= ~(SSPX_CORE_CNT56_SCD_BIT0_TRPT_MAX_MASK);
+	val |= SSPX_CORE_CNT56_SCD_BIT0_TRPT_MAX(0x260);
+	xudc_writel(xudc, val, SSPX_CORE_CNT56);
+
+	val = xudc_readl(xudc, SSPX_CORE_CNT57);
+	val &= ~(SSPX_CORE_CNT57_SCD_BIT1_TRPT_MAX_MASK );
+	val |= SSPX_CORE_CNT57_SCD_BIT1_TRPT_MAX(0x6D6);
+	xudc_writel(xudc, val, SSPX_CORE_CNT57);
+
+	val = xudc_readl(xudc, SSPX_CORE_CNT65);
+	val &= ~(SSPX_CORE_CNT65_TX_SCD_END_TRPT_MID_MASK);
+	val |= SSPX_CORE_CNT65_TX_SCD_END_TRPT_MID(0x4B0);
+	xudc_writel(xudc, val, SSPX_CORE_CNT66);
+
+	val = xudc_readl(xudc, SSPX_CORE_CNT66);
+	val &= ~(SSPX_CORE_CNT66_TX_SCD_BIT0_TRPT_MID_MASK);
+	val |= SSPX_CORE_CNT66_TX_SCD_BIT0_TRPT_MID(0x4B0);
+	xudc_writel(xudc, val, SSPX_CORE_CNT66);
+
+	val = xudc_readl(xudc, SSPX_CORE_CNT67);
+	val &= ~(SSPX_CORE_CNT67_TX_SCD_BIT1_TRPT_MID_MASK);
+	val |= SSPX_CORE_CNT67_TX_SCD_BIT1_TRPT_MID(0x4B0);
+	xudc_writel(xudc, val, SSPX_CORE_CNT67);
+
+	val = xudc_readl(xudc, SSPX_CORE_CNT72);
+	val &= ~(SSPX_CORE_CNT72_SCD_LFPS_TIMEOUT_MASK);
+	val |= SSPX_CORE_CNT72_SCD_LFPS_TIMEOUT(0x10);
+	xudc_writel(xudc, val, SSPX_CORE_CNT72);
+}
+
+static void tegra_xudc_restore_port_speed(struct tegra_xudc *xudc)
+{
+	u32 val;
+
+	/* restore port speed to gen2 */
+	val = xudc_readl(xudc, SSPX_CORE_CNT56);
+	val &= ~(SSPX_CORE_CNT56_SCD_BIT0_TRPT_MAX_MASK);
+	val |= SSPX_CORE_CNT56_SCD_BIT0_TRPT_MAX(0x438);
+	xudc_writel(xudc, val, SSPX_CORE_CNT56);
+
+	val = xudc_readl(xudc, SSPX_CORE_CNT57);
+	val &= ~(SSPX_CORE_CNT57_SCD_BIT1_TRPT_MAX_MASK );
+	val |= SSPX_CORE_CNT57_SCD_BIT1_TRPT_MAX(0x528);
+	xudc_writel(xudc, val, SSPX_CORE_CNT57);
+
+	val = xudc_readl(xudc, SSPX_CORE_CNT65);
+	val &= ~(SSPX_CORE_CNT65_TX_SCD_END_TRPT_MID_MASK);
+	val |= SSPX_CORE_CNT65_TX_SCD_END_TRPT_MID(0xE10);
+	xudc_writel(xudc, val, SSPX_CORE_CNT66);
+
+	val = xudc_readl(xudc, SSPX_CORE_CNT66);
+	val &= ~(SSPX_CORE_CNT66_TX_SCD_BIT0_TRPT_MID_MASK);
+	val |= SSPX_CORE_CNT66_TX_SCD_BIT0_TRPT_MID(0x348);
+	xudc_writel(xudc, val, SSPX_CORE_CNT66);
+
+	val = xudc_readl(xudc, SSPX_CORE_CNT67);
+	val &= ~(SSPX_CORE_CNT67_TX_SCD_BIT1_TRPT_MID_MASK);
+	val |= SSPX_CORE_CNT67_TX_SCD_BIT1_TRPT_MID(0x5a0);
+	xudc_writel(xudc, val, SSPX_CORE_CNT67);
+
+	val = xudc_readl(xudc, SSPX_CORE_CNT72);
+	val &= ~(SSPX_CORE_CNT72_SCD_LFPS_TIMEOUT_MASK);
+	val |= SSPX_CORE_CNT72_SCD_LFPS_TIMEOUT(0x1c21);
+	xudc_writel(xudc, val, SSPX_CORE_CNT72);
+}
+
 static void tegra_xudc_device_mode_on(struct tegra_xudc *xudc)
 {
 	int err;
@@ -631,6 +728,9 @@ static void tegra_xudc_device_mode_off(struct tegra_xudc *xudc)
 
 	reinit_completion(&xudc->disconnect_complete);
 
+	if (xudc->soc->port_speed_quirk)
+		tegra_xudc_restore_port_speed(xudc);
+
 	phy_set_mode_ext(xudc->curr_utmi_phy, PHY_MODE_USB_OTG, USB_ROLE_NONE);
 
 	pls = (xudc_readl(xudc, PORTSC) & PORTSC_PLS_MASK) >>
@@ -3274,6 +3374,9 @@ static void tegra_xudc_device_params_init(struct tegra_xudc *xudc)
 		xudc_writel(xudc, val, BLCG);
 	}
 
+	if (xudc->soc->port_speed_quirk)
+		tegra_xudc_limit_port_speed(xudc);
+
 	/* Set a reasonable U3 exit timer value. */
 	val = xudc_readl(xudc, SSPX_CORE_PADCTL4);
 	val &= ~(SSPX_CORE_PADCTL4_RXDAT_VLD_TIMEOUT_U3_MASK);
@@ -3513,6 +3616,7 @@ static struct tegra_xudc_soc tegra210_xudc_soc_data = {
 	.invalid_seq_num = true,
 	.pls_quirk = true,
 	.port_reset_quirk = true,
+	.port_speed_quirk = false,
 	.has_ipfs = true,
 };
 
@@ -3526,6 +3630,7 @@ static struct tegra_xudc_soc tegra186_xudc_soc_data = {
 	.invalid_seq_num = false,
 	.pls_quirk = false,
 	.port_reset_quirk = false,
+	.port_speed_quirk = false,
 	.has_ipfs = false,
 };
 
@@ -3539,6 +3644,7 @@ static struct tegra_xudc_soc tegra194_xudc_soc_data = {
 	.invalid_seq_num = false,
 	.pls_quirk = false,
 	.port_reset_quirk = false,
+	.port_speed_quirk = true,
 	.has_ipfs = false,
 };
 
-- 
2.7.4

Re: [PATCH V1 4/4] usb: gadget: tegra-xudc: add port_speed_quirk

[Thierry Reding]

[-- Attachment #1: Type: text/plain, Size: 920 bytes --]

On Thu, Apr 16, 2020 at 01:04:20PM +0530, Nagarjuna Kristam wrote:
> Add port_speed_quirk that modify below registers to limit/restore OTG
> port speed to GEN1/GEN2.
> SSPX_CORE_CNT56
> SSPX_CORE_CNT57
> SSPX_CORE_CNT65
> SSPX_CORE_CNT66
> SSPX_CORE_CNT67
> SSPX_CORE_CNT72
> 
> The basic idea is to make SCD intentionally fail, reduce SCD timeout and
> force device transit to TSEQ. Enable this flag to only Tegra194.
> 
> Based on work by WayneChang <waynec@nvidia.com>
> 
> Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
> ---
>  drivers/usb/gadget/udc/tegra-xudc.c | 106 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 106 insertions(+)

You're telling readers what you're doing, but after reading the commit
message, I have no idea why this is being done. Can you provide more
information on why exactly is this needed? Why do we have to limit the
OTG port speed?

Thierry

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH V1 4/4] usb: gadget: tegra-xudc: add port_speed_quirk

[Nagarjuna Kristam]

On 28-04-2020 17:55, Thierry Reding wrote:
> 
> On Thu, Apr 16, 2020 at 01:04:20PM +0530, Nagarjuna Kristam wrote:
>> Add port_speed_quirk that modify below registers to limit/restore OTG
>> port speed to GEN1/GEN2.
>> SSPX_CORE_CNT56
>> SSPX_CORE_CNT57
>> SSPX_CORE_CNT65
>> SSPX_CORE_CNT66
>> SSPX_CORE_CNT67
>> SSPX_CORE_CNT72
>>
>> The basic idea is to make SCD intentionally fail, reduce SCD timeout and
>> force device transit to TSEQ. Enable this flag to only Tegra194.
>>
>> Based on work by WayneChang<waynec@nvidia.com>
>>
>> Signed-off-by: Nagarjuna Kristam<nkristam@nvidia.com>
>> ---
>>   drivers/usb/gadget/udc/tegra-xudc.c | 106 ++++++++++++++++++++++++++++++++++++
>>   1 file changed, 106 insertions(+)
> You're telling readers what you're doing, but after reading the commit
> message, I have no idea why this is being done. Can you provide more
> information on why exactly is this needed? Why do we have to limit the
> OTG port speed?
> 
> Thierry
Will re-word the commit message to explain on why this is needed.

Thanks,
Nagarjuna