Re: [PATCH] mfd: omap-usb-host: AM3715 OHCI needs 120m functional clock

[Ben Dooks <ben.dooks-4yDnlxn2s6sWdaTGBSpHTA@public.gmane.org>]

On 13/10/15 09:45, Roger Quadros wrote:
> Ben,
> 
> On 13/10/15 11:23, Ben Dooks wrote:
>> On 12/10/15 20:19, Tony Lindgren wrote:
>>> * Ben Dooks <ben.dooks-4yDnlxn2s6sWdaTGBSpHTA@public.gmane.org> [151012 11:22]:
>>>> On 12/10/15 18:45, Tony Lindgren wrote:
>>>>> * Ben Dooks <ben.dooks-4yDnlxn2s6sWdaTGBSpHTA@public.gmane.org> [151012 10:38]:
>>>>>> The AM3715 OHCI controller will not function without the EHCI
>>>>>> unit's 120m fclk being enabled. If all the ports in the system
>>>>>> are set to OHCI then the 120m_fclk will not get enabled and no
>>>>>> devices are detected.
>>>>>>
>>>>>> Add a new (optional) property to signal the system must enable
>>>>>> the 120m_fck for OHCI so that if no EHCI ports are signalled
>>>>>> then the 120m_fclk should be enabled.
>>>>>>
>>>>>> We have found no information about why this is necessary, but
>>>>>> it is suspected the EHCI controller does not complete the initial
>>>>>> reset sequence and therefore does not hand control of the USB
>>>>>> port back.
>>>>>>
>>>>>> Signed-off-by: Ben Dooks <ben.dooks-4yDnlxn2s6sWdaTGBSpHTA@public.gmane.org>
>>>>>> ---
>>>>>>  Documentation/devicetree/bindings/usb/omap-usb.txt | 3 +++
>>>>>>  drivers/mfd/omap-usb-host.c                        | 4 ++++
>>>>>>  2 files changed, 7 insertions(+)
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/usb/omap-usb.txt b/Documentation/devicetree/bindings/usb/omap-usb.txt
>>>>>> index 38d9bb8..fb5fea5 100644
>>>>>> --- a/Documentation/devicetree/bindings/usb/omap-usb.txt
>>>>>> +++ b/Documentation/devicetree/bindings/usb/omap-usb.txt
>>>>>> @@ -23,6 +23,9 @@ OMAP MUSB GLUE
>>>>>>  Optional properties:
>>>>>>   - ctrl-module : phandle of the control module this glue uses to write to
>>>>>>     mailbox
>>>>>> + - ti,ohci-needs-120m-fck : bool, enable the 120m ehci clock even if just
>>>>>> +   using ohci. Needed for AM3517 in OHCI only mode.
>>>>>> +
>>>>>>  
>>>>>>  SOC specific device node entry
>>>>>>  usb_otg_hs: usb_otg_hs@4a0ab000 {
>>>>>> diff --git a/drivers/mfd/omap-usb-host.c b/drivers/mfd/omap-usb-host.c
>>>>>> index 1d924d1..13880cf 100644
>>>>>> --- a/drivers/mfd/omap-usb-host.c
>>>>>> +++ b/drivers/mfd/omap-usb-host.c
>>>>>> @@ -680,6 +680,10 @@ static int usbhs_omap_probe(struct platform_device *pdev)
>>>>>>  				need_logic_fck |= true;
>>>>>>  		}
>>>>>>  
>>>>>> +		/* The AM3517 requries the 120m-fck active to allow the OHCI to work */
>>>>>> +		if (of_property_read_bool(dev->of_node, "ti,ohci-needs-120m-fck"))
>>>>>> +			need_logic_fck |= true;
>>>>>> +
>>>>>>  		if (need_logic_fck) {
>>>>>>  			omap->ehci_logic_fck = devm_clk_get(dev,
>>>>>>  							    "usbhost_120m_fck");
>>>>>
>>>>> Hmm why not just use the standard device tree clocks property and then do
>>>>> clk_get_rate() on the clock?
>>>>
>>>> I don't see that helps enabling the clock. The code decideds if
>>>> no EHCI ports in use that it doesn't need to enable the EHCI fclk.
>>>
>>> Right, you need to do clk_prepare_enable() in it first? :)
>>
>> No, if that was the case the driver would never work for the EHCI case.
>>
>> The issue is:
>>
>> 1) All ports on the system are set to OHCI
>> 2) The omap-usb-host.c does not touch usbhost_120m_fck if no EHCI ports
>> 3) The OHCI fails to detect any devices due to point 2.
>>
> 
> Instead of your existing approach why not just modify the preceeding
> if condition that sets need_logic_fck to suit the OHCI case.
> 
> That way you don't need to add a new DT binding.
> 
> The old assumption was that 120m_fck logic clock is only needed for
> EHCI mode but it looks like OHCI mode needs it as well.
> 
> You should also rename omap->ehci_logic_fck to omap->hci_logic_fck
> as it is no longer ehci specific.

Thanks, will go and have a look at the manual later as didn't see two
separate 120m clocks when looking.


-- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius
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