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

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

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.

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