Re: [PATCH v1 1/3] usb: dwc2: reset AHB hclk domain before init

From: John Youn
Date: Fri Aug 14 2015 - 15:41:21 EST

On 8/13/2015 8:29 PM, Yunzhi Li wrote:
> 在 2015/8/14 8:09, John Youn 写道:
>> On 8/11/2015 12:57 AM, Yunzhi Li wrote:
>>> We initiate dwc2 usb controller in BIOS, when kernel driver
>>> start-up we should reset AHB hclk domain to reset all AHB
>>> interface registers to default. Without this the FIFO value
>>> setting might be incorrect because calculating FIFO size need the
>>> power-on value of GRXFSIZ/GNPTXFSIZ/HPTXFSIZ registers.
>>> This patch could avoid warnning massage like in rk3288 platform:
>>> [ 2.074764] dwc2 ff580000.usb: 256 invalid for
>>> host_perio_tx_fifo_size. Check HW configuration.
>>> ......
>> I didn't receive the other two patches in this series so I was
>> confused about where the "ahb_reset" was coming from when I
>> replied to your other patch.
>> I see you changed the name and documented the DT so never mind.
>> Another thing is that there probably shouldn't be a debug
>> message on the IS_ERR condition since that is the common case
>> and of no interest to other platforms.
>> The other two resets you added aren't used by the driver
>> anywhere right? Maybe those should be left out until they are.
>> John
> Hi John ,
> Here is the other two patches :
> ahb_reset is hreset_n signal of dwc2 IP. Our rk3288 SoC implement
> connect this signal to a special
> register in clock ang reset unit (CRU) module, set this register will
> reset dwc2 control and status registers(CSR)
> to default value. You could find more info in <<DesignWare Cores USB 2.0
> Hi Speed On-TheGo (OTG) Databook 3.10a>>
> 4.4.1 System Clock and Reset Signals.
> Our problem is that dwc2_get_hwparams() reads fifo size registers and
> reguards it as the power-on reset value,
> then dwc2_set_param_host_perio_tx_fifo_size() will check this value and
> make sure the new fifo size value is no bigger
> than the power-on reset value. But we init and set these fifo registers
> in BIOS, so here hw->xxx_fifo_size is not the
> real power-on reset vaule. So we hope to reset CSR before
> dwc2_get_hwparams().
> I have another ideal: we might use GRSTCTL.CSftRst instead of hreset_n
> to reset dwc2 CSR.

Yes, please try doing that before calling dwc2_get_hwparams().
Maybe by calling dwc2_core_reset(). If that works for you, I think
it would be better.


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