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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:     Felipe Balbi <felipe.balbi@linux.intel.com>,
        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: <0d8de3e0-341b-f751-909d-22aa16e91717@samsung.com>
Date:   Tue, 3 Aug 2021 11:40:00 +0200
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References: <CGME20210716050132eucas1p285949f9a73764b173c29ad0fa8502f23@eucas1p2.samsung.com>
        <20210716050127.4406-1-m.szyprowski@samsung.com>
        <a7efdf13-48bb-db21-5755-ebbbe2614f78@synopsys.com>
Precedence: bulk

Hi Minas,

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

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