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From: Felipe Balbi <balbi@kernel.org>
To: John Stultz <john.stultz@linaro.org>,
	lkml <linux-kernel@vger.kernel.org>
Cc: Yu Chen <chenyu56@huawei.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	ShuFan Lee <shufan_lee@richtek.com>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Chunfeng Yun <chunfeng.yun@mediatek.com>,
	Hans de Goede <hdegoede@redhat.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Jun Li <lijun.kernel@gmail.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Jack Pham <jackp@codeaurora.org>,
	linux-usb@vger.kernel.org, devicetree@vger.kernel.org,
	John Stultz <john.stultz@linaro.org>
Subject: Re: [PATCH v4 2/9] usb: dwc3: Execute GCTL Core Soft Reset while switch modes
Date: Tue, 29 Oct 2019 11:09:47 +0200	[thread overview]
Message-ID: <87pnifj4tg.fsf@gmail.com> (raw)
In-Reply-To: <20191028215919.83697-3-john.stultz@linaro.org>

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Hi,

John Stultz <john.stultz@linaro.org> writes:
> From: Yu Chen <chenyu56@huawei.com>
>
> On the HiKey960, we need to do a GCTL soft reset when
> switching modes.
>
> Jack Pham also noted that in the Synopsys databook it
> mentions performing a GCTL CoreSoftReset when changing the
> PrtCapDir between device & host modes.
>
> So this patch always does a GCTL Core Soft Reset when
> changing the mode.
>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> CC: ShuFan Lee <shufan_lee@richtek.com>
> Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Chunfeng Yun <chunfeng.yun@mediatek.com>
> Cc: Yu Chen <chenyu56@huawei.com>
> Cc: Felipe Balbi <balbi@kernel.org>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
> Cc: Jun Li <lijun.kernel@gmail.com>
> Cc: Valentin Schneider <valentin.schneider@arm.com>
> Cc: Jack Pham <jackp@codeaurora.org>
> Cc: linux-usb@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> Signed-off-by: Yu Chen <chenyu56@huawei.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v3: Remove quirk conditional, as Jack Pham noted the
>     Synopsis databook states this should be done generally.
>     Also, at Jacks' suggestion, make the reset call before
>     changing the prtcap direction.
> ---
>  drivers/usb/dwc3/core.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 999ce5e84d3c..a039e35ec7ad 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -112,6 +112,19 @@ void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode)
>  	dwc->current_dr_role = mode;
>  }
>  
> +static void dwc3_gctl_core_soft_reset(struct dwc3 *dwc)
> +{
> +	u32 reg;
> +
> +	reg = dwc3_readl(dwc->regs, DWC3_GCTL);
> +	reg |= DWC3_GCTL_CORESOFTRESET;
> +	dwc3_writel(dwc->regs, DWC3_GCTL, reg);
> +
> +	reg = dwc3_readl(dwc->regs, DWC3_GCTL);
> +	reg &= ~DWC3_GCTL_CORESOFTRESET;
> +	dwc3_writel(dwc->regs, DWC3_GCTL, reg);
> +}
> +
>  static void __dwc3_set_mode(struct work_struct *work)
>  {
>  	struct dwc3 *dwc = work_to_dwc(work);
> @@ -154,6 +167,9 @@ static void __dwc3_set_mode(struct work_struct *work)
>  
>  	spin_lock_irqsave(&dwc->lock, flags);
>  
> +	/* Execute a GCTL Core Soft Reset when switch mode */
> +	dwc3_gctl_core_soft_reset(dwc);
> +

This is totally unnecessary. We have several platforms supporting dual
role *without* this trick. The only reason why the databook mentions a
reset is because some registers are shadowed, meaning that they share
the same physical space and just appear as different things for SW. The
reason being that Synopsys wanted to reduce the area of the IP and
decided to shadow registers which are mutually exclusive.

-- 
balbi

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  reply	other threads:[~2019-10-29  9:10 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-28 21:59 [PATCH v4 0/9] Prereqs for HiKey960 USB support John Stultz
2019-10-28 21:59 ` [PATCH v4 1/9] dt-bindings: usb: rt1711h: Add connector bindings John Stultz
2019-10-28 21:59 ` [PATCH v4 2/9] usb: dwc3: Execute GCTL Core Soft Reset while switch modes John Stultz
2019-10-29  9:09   ` Felipe Balbi [this message]
2019-10-29 21:21     ` John Stultz
2019-10-28 21:59 ` [PATCH v4 3/9] usb: dwc3: Increase timeout for CmdAct cleared by device controller John Stultz
2019-10-29  9:11   ` Felipe Balbi
2019-10-29 21:17     ` John Stultz
2020-05-06  9:00       ` Jun Li
2020-05-06 22:27         ` John Stultz
2020-05-07  3:08           ` Jun Li
2020-05-08 12:22             ` Jun Li
2020-05-08 12:35               ` Felipe Balbi
2020-05-09  8:28                 ` Jun Li
2020-05-08 12:33         ` Felipe Balbi
2020-05-09  8:10           ` Jun Li
2020-05-15  9:31             ` Felipe Balbi
2020-05-15 10:07               ` Jun Li
2020-05-15 10:41                 ` Felipe Balbi
2020-05-16  0:25                 ` Thinh Nguyen
2020-05-16  7:12                   ` Felipe Balbi
2020-05-16  9:20                     ` Jun Li
2020-05-16 11:57                       ` Felipe Balbi
2020-05-19  2:24                         ` Jun Li
2020-05-19  6:28                           ` Thinh Nguyen
2020-05-19  6:46                             ` Thinh Nguyen
2020-05-19  7:39                               ` Jun Li
2020-05-21  1:07                                 ` Thinh Nguyen
2020-05-21  1:55                                   ` Thinh Nguyen
2020-05-21  6:20                                     ` Felipe Balbi
2020-05-21  6:22                                       ` Felipe Balbi
2020-05-21  7:47                                         ` Jun Li
2020-05-21  7:33                                     ` Jun Li
2019-10-28 21:59 ` [PATCH v4 4/9] dt-bindings: usb: dwc3: Allow clock list & resets to be more flexible John Stultz
2019-10-28 21:59 ` [PATCH v4 5/9] usb: dwc3: Rework clock initialization " John Stultz
2019-10-29  9:13   ` Felipe Balbi
2019-10-29 16:08     ` John Stultz
2019-10-30  9:02       ` Felipe Balbi
2019-11-07 21:53     ` Rob Herring
2019-10-28 21:59 ` [PATCH v4 6/9] usb: dwc3: Rework resets " John Stultz
2019-10-29  9:17   ` Felipe Balbi
2019-10-29 18:05     ` John Stultz
2019-10-30  9:01       ` Felipe Balbi
2019-11-07 21:45         ` Rob Herring
2019-10-28 21:59 ` [PATCH v4 7/9] usb: dwc3: Registering a role switch in the DRD code John Stultz
2019-10-29  9:21   ` Felipe Balbi
2019-11-07 23:20     ` John Stultz
2019-10-28 21:59 ` [PATCH v4 8/9] dt-bindings: usb: generic: Add role-switch-default-host binding John Stultz
2019-10-29  9:23   ` Felipe Balbi
2019-10-29 18:26     ` John Stultz
2019-10-28 21:59 ` [PATCH v4 9/9] usb: dwc3: Add host-mode as default support John Stultz
2019-10-29  9:25   ` Felipe Balbi
2019-11-07 22:23     ` John Stultz

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