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Subject: Re: [PATCH] usb: dwc2: Skip clock gating on Samsung SoCs
To:     Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-samsung-soc@vger.kernel.org" 
        <linux-samsung-soc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc:     Artur Petrosyan <Arthur.Petrosyan@synopsys.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Krzysztof Kozlowski <krzk@kernel.org>
From:   Marek Szyprowski <m.szyprowski@samsung.com>
Message-ID: <26099de1-826f-42bf-0de7-759a47faf4a0@samsung.com>
Date:   Wed, 4 Aug 2021 13:29:31 +0200
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References: <CGME20210716050132eucas1p285949f9a73764b173c29ad0fa8502f23@eucas1p2.samsung.com>
        <20210716050127.4406-1-m.szyprowski@samsung.com>
        <a7efdf13-48bb-db21-5755-ebbbe2614f78@synopsys.com>
        <0d8de3e0-341b-f751-909d-22aa16e91717@samsung.com>
        <19ddcd51-1f1c-52a8-8eaf-dabf7425d395@synopsys.com>
Precedence: bulk

Hi

On 03.08.2021 12:08, Minas Harutyunyan wrote:
> On 8/3/2021 1:40 PM, Marek Szyprowski wrote:
>> On 16.07.2021 16:54, Minas Harutyunyan wrote:
>>> On 7/16/2021 9:01 AM, Marek Szyprowski wrote:
>>>> Commit 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr
>>>> function.") changed the way the driver handles power down modes in a such
>>>> way that it uses clock gating when no other power down mode is available.
>>>>
>>>> This however doesn't work well on the DWC2 implementation used on the
>>>> Samsung SoCs. When a clock gating is enabled, system hangs. It looks that
>>>> the proper clock gating requires some additional glue code in the shared
>>>> USB2 PHY and/or Samsung glue code for the DWC2. To restore driver
>>>> operation on the Samsung SoCs simply skip enabling clock gating mode
>>>> until one finds what is really needed to make it working reliably.
>>>>
>>>> Fixes: 0112b7ce68ea ("usb: dwc2: Update dwc2_handle_usb_suspend_intr function.")
>>>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>>> ---
>>>>      drivers/usb/dwc2/core.h      | 4 ++++
>>>>      drivers/usb/dwc2/core_intr.c | 3 ++-
>>>>      drivers/usb/dwc2/hcd.c       | 6 ++++--
>>>>      drivers/usb/dwc2/params.c    | 1 +
>>>>      4 files changed, 11 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h
>>>> index ab6b815e0089..483de2bbfaab 100644
>>>> --- a/drivers/usb/dwc2/core.h
>>>> +++ b/drivers/usb/dwc2/core.h
>>>> @@ -383,6 +383,9 @@ enum dwc2_ep0_state {
>>>>       *			0 - No (default)
>>>>       *			1 - Partial power down
>>>>       *			2 - Hibernation
>>>> + * @no_clock_gating:	Specifies whether to avoid clock gating feature.
>>>> + *			0 - No (use clock gating)
>>>> + *			1 - Yes (avoid it)
>>>>       * @lpm:		Enable LPM support.
>>>>       *			0 - No
>>>>       *			1 - Yes
>>>> @@ -480,6 +483,7 @@ struct dwc2_core_params {
>>>>      #define DWC2_POWER_DOWN_PARAM_NONE		0
>>>>      #define DWC2_POWER_DOWN_PARAM_PARTIAL		1
>>>>      #define DWC2_POWER_DOWN_PARAM_HIBERNATION	2
>>>> +	bool no_clock_gating;
>>>>      
>>>>      	bool lpm;
>>>>      	bool lpm_clock_gating;
>>>> diff --git a/drivers/usb/dwc2/core_intr.c b/drivers/usb/dwc2/core_intr.c
>>>> index a5ab03808da6..a5c52b237e72 100644
>>>> --- a/drivers/usb/dwc2/core_intr.c
>>>> +++ b/drivers/usb/dwc2/core_intr.c
>>>> @@ -556,7 +556,8 @@ static void dwc2_handle_usb_suspend_intr(struct dwc2_hsotg *hsotg)
>>>>      				 * If neither hibernation nor partial power down are supported,
>>>>      				 * clock gating is used to save power.
>>>>      				 */
>>>> -				dwc2_gadget_enter_clock_gating(hsotg);
>>>> +				if (!hsotg->params.no_clock_gating)
>>>> +					dwc2_gadget_enter_clock_gating(hsotg);
>>>>      			}
>>>>      
>>>>      			/*
>>>> diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
>>>> index 035d4911a3c3..2a7828971d05 100644
>>>> --- a/drivers/usb/dwc2/hcd.c
>>>> +++ b/drivers/usb/dwc2/hcd.c
>>>> @@ -3338,7 +3338,8 @@ int dwc2_port_suspend(struct dwc2_hsotg *hsotg, u16 windex)
>>>>      		 * If not hibernation nor partial power down are supported,
>>>>      		 * clock gating is used to save power.
>>>>      		 */
>>>> -		dwc2_host_enter_clock_gating(hsotg);
>>>> +		if (!hsotg->params.no_clock_gating)
>>>> +			dwc2_host_enter_clock_gating(hsotg);
>>>>      		break;
>>>>      	}
>>>>      
>>>> @@ -4402,7 +4403,8 @@ static int _dwc2_hcd_suspend(struct usb_hcd *hcd)
>>>>      		 * If not hibernation nor partial power down are supported,
>>>>      		 * clock gating is used to save power.
>>>>      		 */
>>>> -		dwc2_host_enter_clock_gating(hsotg);
>>>> +		if (!hsotg->params.no_clock_gating)
>>>> +			dwc2_host_enter_clock_gating(hsotg);
>>>>      
>>>>      		/* After entering suspend, hardware is not accessible */
>>>>      		clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
>>>> diff --git a/drivers/usb/dwc2/params.c b/drivers/usb/dwc2/params.c
>>>> index 67c5eb140232..59e119345994 100644
>>>> --- a/drivers/usb/dwc2/params.c
>>>> +++ b/drivers/usb/dwc2/params.c
>>>> @@ -76,6 +76,7 @@ static void dwc2_set_s3c6400_params(struct dwc2_hsotg *hsotg)
>>>>      	struct dwc2_core_params *p = &hsotg->params;
>>>>      
>>>>      	p->power_down = DWC2_POWER_DOWN_PARAM_NONE;
>>>> +	p->no_clock_gating = true;
>>>>      	p->phy_utmi_width = 8;
>>>>      }
>>>>      
>>>>
>>> In which mode host/device you see the issue?
>> I do my test in my device mode.
>>> What is your core version? Please provide GHWCFG1-4 registers values.
>> This is a result of dwc2_dump_global_registers() added just after
>> dwc2_lowlevel_hw_enable() in dwc2_driver_probe():
>>
>> dwc2 12480000.hsotg: Core Global Registers
>>
>> dwc2 12480000.hsotg: GOTGCTL      @0xE0260000 : 0x000D0000
>> dwc2 12480000.hsotg: GOTGINT      @0xE0260004 : 0x00000000
>> dwc2 12480000.hsotg: GAHBCFG      @0xE0260008 : 0x00000027
>> dwc2 12480000.hsotg: GUSBCFG      @0xE026000C : 0x0000540F
>> dwc2 12480000.hsotg: GRSTCTL      @0xE0260010 : 0x80000040
>> dwc2 12480000.hsotg: GINTSTS      @0xE0260014 : 0x54008428
>> dwc2 12480000.hsotg: GINTMSK      @0xE0260018 : 0x800C3800
>> dwc2 12480000.hsotg: GRXSTSR      @0xE026001C : 0x616EC77D
>> dwc2 12480000.hsotg: GRXFSIZ      @0xE0260024 : 0x00000400
>> dwc2 12480000.hsotg: GNPTXFSIZ    @0xE0260028 : 0x04000400
>> dwc2 12480000.hsotg: GNPTXSTS     @0xE026002C : 0x00080400
>> dwc2 12480000.hsotg: GI2CCTL      @0xE0260030 : 0x00000000
>> dwc2 12480000.hsotg: GPVNDCTL     @0xE0260034 : 0x00000000
>> dwc2 12480000.hsotg: GGPIO        @0xE0260038 : 0x00000000
>> dwc2 12480000.hsotg: GUID         @0xE026003C : 0x00000000
>> dwc2 12480000.hsotg: GSNPSID      @0xE0260040 : 0x4F54281A
>> dwc2 12480000.hsotg: GHWCFG1      @0xE0260044 : 0x00000000
>> dwc2 12480000.hsotg: GHWCFG2      @0xE0260048 : 0x228FFC50
>> dwc2 12480000.hsotg: GHWCFG3      @0xE026004C : 0x1E8084E8
>> dwc2 12480000.hsotg: GHWCFG4      @0xE0260050 : 0xFFF08030
>> dwc2 12480000.hsotg: GLPMCFG      @0xE0260054 : 0x00000000
>> dwc2 12480000.hsotg: GPWRDN       @0xE0260058 : 0x00000000
>> dwc2 12480000.hsotg: GDFIFOCFG    @0xE026005C : 0x00000000
>> dwc2 12480000.hsotg: HPTXFSIZ     @0xE0260100 : 0x00000000
>> dwc2 12480000.hsotg: PCGCTL       @0xE0260E00 : 0x00000000
>> dwc2 12480000.hsotg: dwc2_check_params: Invalid parameter besl=1
>> dwc2 12480000.hsotg: dwc2_check_params: Invalid parameter
>> g_np_tx_fifo_size=1024
>> dwc2 12480000.hsotg: EPs: 16, dedicated fifos, 7808 entries in SPRAM
>>> Is the issue seen because of programming PCGCTL.PCGCTL_GATEHCLK bit
>>> only? To check it, could you please comment this bit setting/resetting
>>> in clock gating functions:
>>> dwc2_host_exit_clock_gating()
>>> dwc2_host_enter_clock_gating()
>>> dwc2_gadget_exit_clock_gating()
>>> dwc2_gadget_enter_clock_gating()
>> After removing programming PCGCTL.PCGCTL_GATEHCLK bit in the above
>> functions, everything works fine.
>>
>> Best regards
>>
> Thank you for testing and confirm my expectations.
>
> There are 3 options:
> 1. Do not update your patch and accept it
> 2. Update your patch to exclude programming of PCGCTL.PCGCTL_GATEHCLK
> bit based on hsotg->params.no_clock_gating in all
> ..._exit/enter_clock_gating functions
> 3. More radical solution, to have really ...POWER_DOWN_NONE case:
> - rename DWC2_POWER_DOWN_PARAM_NONE to DWC2_POWER_DOWN_CLOCK_GATING in
> whole driver;
> - define new power state "#define DWC2_POWER_DOWN_PARAM_NONE	-1"
> - and for all platforms who doesn't want to have any power optimization
> keep:
>       p->power_down = DWC2_POWER_DOWN_PARAM_NONE;
>
>
> I would prefer option 3. What you think about this solution? Can you
> implement it (I guess it required 5 min) and test on your platform.

Okay, I will do the 3rd option. However, the $subject patch has been 
already merged to v5.14-rc3 some time ago, so I will do that on top of 
v5.14-rc3.

Best regards

-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland