On Thu, Aug 12, 2021 at 01:26:35AM -0700, Jack Pham wrote:
> On DWC_usb3 revisions 3.00a and newer (including DWC_usb31 and
> DWC_usb32) the GUCTL1 register gained the DEV_DECOUPLE_L1L2_EVT
> field (bit 31) which when enabled allows the controller in device
> mode to treat USB 2.0 L1 LPM & L2 events separately.
>
> After commit d1d90dd27254 ("usb: dwc3: gadget: Enable suspend
> events") the controller will now receive events (and therefore
> interrupts) for every state change when entering/exiting either
> L1 or L2 states. Since L1 is handled entirely by the hardware
> and requires no software intervention, there is no need to even
> enable these events and unnecessarily notify the gadget driver.
> Enable the aforementioned bit to help reduce the overall interrupt
> count for these L1 events that don't need to be handled while
> retaining the events for full L2 suspend/wakeup.
Hi folks in To:
I'd like to request if any of you could help test this patch on your
boards to help make sure it doesn't cause any regressions since I know
some of the recent dwc3 patches from Qualcomm have been found to break
other devices :(. So I'm hoping to avoid that even for a patch as
small as this.
Hoping this could be tried out on boards/SoCs such as db845c, hikey960,
Exynos, the Intel "lakes", etc. Ideally this needs validation with a
high-speed connection to a USB 3.x host, which increases the chances
that USB 2.0 Link Power Management is supported.
The overall goal of this patch is to eliminate events generated for
L1 entry/exit, so we should see a slight reduction in interrupt counts
when checking `grep dwc3 /proc/interrupts` for comparable traffic.
Appreciate any feedback and help in testing!
Thanks,
Jack
> Signed-off-by: Jack Pham <jackp@xxxxxxxxxxxxxx>
> ---
> drivers/usb/dwc3/core.c | 9 +++++++++
> drivers/usb/dwc3/core.h | 5 +++--
> 2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index ba74ad7f6995..719dac228703 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1050,6 +1050,15 @@ static int dwc3_core_init(struct dwc3 *dwc)
> if (!DWC3_VER_IS_PRIOR(DWC3, 290A))
> reg |= DWC3_GUCTL1_DEV_L1_EXIT_BY_HW;
>
> + /*
> + * Decouple USB 2.0 L1 & L2 events which will allow for
> + * gadget driver to only receive U3/L2 suspend & wakeup
> + * events and prevent the more frequent L1 LPM transitions
> + * from interrupting the driver.
> + */
> + if (!DWC3_VER_IS_PRIOR(DWC3, 300A))
> + reg |= DWC3_GUCTL1_DEV_DECOUPLE_L1L2_EVT;
> +
> if (dwc->dis_tx_ipgap_linecheck_quirk)
> reg |= DWC3_GUCTL1_TX_IPGAP_LINECHECK_DIS;
>
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index 5991766239ba..356b94a7ec70 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -256,9 +256,10 @@
> #define DWC3_GUCTL_HSTINAUTORETRY BIT(14)
>
> /* Global User Control 1 Register */
> -#define DWC3_GUCTL1_PARKMODE_DISABLE_SS BIT(17)
> +#define DWC3_GUCTL1_DEV_DECOUPLE_L1L2_EVT BIT(31)
> #define DWC3_GUCTL1_TX_IPGAP_LINECHECK_DIS BIT(28)
> -#define DWC3_GUCTL1_DEV_L1_EXIT_BY_HW BIT(24)
> +#define DWC3_GUCTL1_DEV_L1_EXIT_BY_HW BIT(24)
> +#define DWC3_GUCTL1_PARKMODE_DISABLE_SS BIT(17)
>
> /* Global Status Register */
> #define DWC3_GSTS_OTG_IP BIT(10)
> --
> 2.24.0
>
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