[PATCH v2 17/29] drm: bridge: dw-hdmi: Refactor PHY power handling

[Jose Abreu]

Hi Laurent,


On 05-01-2017 12:29, Laurent Pinchart wrote:
> Hi Jose,
>
> On Tuesday 20 Dec 2016 12:17:23 Jose Abreu wrote:
>> On 20-12-2016 11:45, Russell King - ARM Linux wrote:
>>> On Tue, Dec 20, 2016 at 03:33:48AM +0200, Laurent Pinchart wrote:
>>>> Instead of spreading version-dependent PHY power handling code around,
>>>> group it in two functions to power the PHY on and off and use them
>>>> through the driver.
>>>>
>>>> Powering off the PHY at the beginning of the setup phase is currently
>>>> split in two locations for first and second generation PHYs, group all
>>>> the operations in the dw_hdmi_phy_init() function.
>>> This changes the behaviour of the driver.
>>>
>>>> +static void dw_hdmi_phy_power_off(struct dw_hdmi *hdmi)
>>>> +{
>>>> +	if (hdmi->phy->gen == 1) {
>>>> +		dw_hdmi_phy_enable_tmds(hdmi, 0);
>>>> +		dw_hdmi_phy_enable_powerdown(hdmi, true);
>>>> +	} else {
>>>> +		dw_hdmi_phy_gen2_txpwron(hdmi, 0);
>>>> +		dw_hdmi_phy_gen2_pddq(hdmi, 1);
>>>> +	}
>>>> +}
>>>> @@ -1290,9 +1302,7 @@ static void dw_hdmi_phy_disable(struct dw_hdmi
>>>> *hdmi)
>>>>
>>>>  	if (!hdmi->phy_enabled)
>>>>  	
>>>>  		return;
>>>>
>>>> -	dw_hdmi_phy_enable_tmds(hdmi, 0);
>>>> -	dw_hdmi_phy_enable_powerdown(hdmi, true);
>>>> -
>>>> +	dw_hdmi_phy_power_off(hdmi);
>>> This makes dw_hdmi_phy_disable() power down a gen2 phy.
>>>
>>> The iMX6 has a DW_HDMI_PHY_DWC_HDMI_3D_TX_PHY phy, which you list as a
>>> gen2 phy.  I've been carrying this change for a while, which I've had
>>> to revert (and finally expunge), as it causes problems on iMX6:
>>>
>>> @@ -1112,6 +1112,14 @@ static void dw_hdmi_phy_disable(struct dw_hdmi
>>> *hdmi)> 
>>>         if (!hdmi->phy_enabled)
>>>         
>>>                 return;
>>>
>>> +       /* Actually set the phy into low power mode */
>>> +       dw_hdmi_phy_gen2_txpwron(hdmi, 0);
>>> +
>>> +       /* FIXME: We should wait for TX_READY to be deasserted */
>>> +
>>> +       dw_hdmi_phy_gen2_pddq(hdmi, 1);
>>> +
>>> +       /* This appears to have no effect on iMX6 */
>>>
>>>         dw_hdmi_phy_enable_tmds(hdmi, 0);
>>>         dw_hdmi_phy_enable_powerdown(hdmi, true);
>>>
>>> So, I think your change here will cause problems for iMX6.
>>>
>>> From what I remember, it seems that iMX6 has issues with RXSENSE/HPD
>>> bouncing when the PHY is powered down.  I can't promise when I'll be
>>> able to check for that again.
>> Indeed TX_READY must be low before asserting pddq.
> The TX_READY signal is documented in the i.MX6 datasheet as being a PHY output 
> signal, but there seems to be no HDMI TX register from which its state can be 
> read. Do I need to poll the HDMI_PHY_PTRPT_ENBL register through I2C ? How 
> long is the PHY expected to take to set TX_READY to 0 ?

TX_READY can be read from register 0x1A of phy, BIT(2) (through
I2C). Not sure if same offset for all phys though.

Best regards,
Jose Miguel Abreu

>
>> HPD and RXSENSE should work in power down mode by enabling enhpdrxsense
>> bit in phy_conf0 BUT to enter power down you must disable TX_PWRON,
>> enhpdrxsense and enable PDDQ and PHY_RESET. Only after doing this (and
>> consequently entering power down mode) you can enable again enhpdrxsense.
> Thanks, I'll give it a try.
>