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Subject: Re: [PATCH] usb: dwc2: Skip clock gating on Samsung SoCs
To:     Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>,
        Marek Szyprowski <m.szyprowski@samsung.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>
References: <CGME20210716050132eucas1p285949f9a73764b173c29ad0fa8502f23@eucas1p2.samsung.com>
 <20210716050127.4406-1-m.szyprowski@samsung.com>
 <e2fc4d3f-2f64-1d7e-5816-0275da23d6fa@canonical.com>
 <6fb5313e-b2c0-7b3e-84f7-6333216f4292@synopsys.com>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Message-ID: <bb750c51-c01a-fb95-4ad5-2fd3f1c625f9@canonical.com>
Date:   Fri, 16 Jul 2021 11:12:16 +0200
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On 16/07/2021 11:07, Minas Harutyunyan wrote:
> Hi Krzysztof,
> 
> On 7/16/2021 12:10 PM, Krzysztof Kozlowski wrote:
>> On 16/07/2021 07:01, 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(-)
>>>
>>
>>
>> Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
>>
> What mean your "Acked-by" tag? Do you want to mention that this commit 
> "Tested-by" or "Reviewed-by" by you?

My "Acked-by" means exactly what Linux process defines:
https://elixir.bootlin.com/linux/latest/source/Documentation/process/submitting-patches.rst#L426

Acked-by is neither Tested-by nor Reviewed-by. For the definition
of these other tags, please also see link above.

Best regards,
Krzysztof