[U-Boot] [PATCH 15/17] sunxi: Ippo_q8h defconfigs: Enable the LCD panel found on these tablets.

[Hans de Goede]

Hi,

On 01-01-15 03:35, Chen-Yu Tsai wrote:
> Hi Hans,
>
> On Wed, Dec 31, 2014 at 7:22 PM, Hans de Goede <hdegoede at redhat.com> wrote:

<snip>

>>> I also compared the config settings from your patches with the
>>> automatically generated records and noticed some inconsistencies.
>>>
>>> For example, Ippo_q8h_v1_2_defconfig :
>>>
>>> === A part of your patch:
>>>
>>> +CONFIG_VIDEO_LCD_POWER="PH7"
>>> +CONFIG_VIDEO_LCD_BL_EN="PH6"
>>> +CONFIG_VIDEO_LCD_BL_PWM="PH0"
>>>
>>> === My script:
>>>
>>> # warning: could not decode 'lcd_power' (port:power2<1><0><default><1>)
>>> CONFIG_VIDEO_LCD_BL_EN="PH6"
>>> # warning: 'lcd_pwm' gpio extracted from 'pwm0_para' section
>>> CONFIG_VIDEO_LCD_BL_PWM="PH0"
>>> # warning: 'lcd_gpio_0' = 'port:PH07<1><0><default><1>'
>>>
>>> ===
>>>
>>> In both cases we have references to PH0/PH6/PH7 pins, however my
>>> script would pick "AXP0-2" for CONFIG_VIDEO_LCD_POWER (taking your
>>> advise), while the role of 'lcd_gpio_0' is not quite clear.
>>> And this is Allwinner A23, which does not use even use AXP209 PMIC.
>>>
>>> What is actually going on with the AXP GPIO and power routing? Is AXP
>>> GPIO really doing what we expect it to be doing?
>>
>>
>> What is likely going on here is that we do not need PH7 at all, when I
>> first wrote the LCD support for the Ippo_q8h_v1_2 I did not have any
>> axp-gpio support at all, so I decided to just ignore the axp gpio listed
>> in the fex and see if things would work without it, and they did, so it
>> seems that either the LCD does not have a power/enable pin for the lcd
>> itself, or at least it is ok to leave the pin floating (which is the axp
>> gpio default).
>
> On the A23 reference design, LCD power is only controlled by enabling
> the AXP LDO output. Downstream just uses the LDO voltage level, rather
> than a GPIO, to enable the discrete regulators. Since the AXP is already
> software controllable, it makes sense. But it's possible on some boards
> we may need it, when the LCD power is derived from a common 5V or 3.3V
> source.

Ok.

>> As for the lcd_gpio_# entries in the fex, looking at the linux-sunxi code,
>> it seems that they are initialized to the value specified in the fex once,
>> which for the Ippo_q8h_v1_2 means setting the gpio to output high once,
>> which we do effectively be assigning PH7 to CONFIG_VIDEO_LCD_POWER (and
>> I need to test if this is really necessary).
>
> PH7 in the reference design drives LCD_RST. I guess leaving it floating
> doesn't assert reset in the LCD driver. IMO, LCD_RESET would be a better
> name. It's what schematics use.

Ok, note that the current defconfig for the q8h is driving it, but is using
CONFIG_VIDEO_LCD_POWER to drive it, which certainly seems the wrong name for
it.

>> I agree that this is confusing, and that we should probably add something
>> akin to lcd_gpio_0 to u-boot so that we've a 1:1 translation.
>>
>> A quick grep:
>>
>> [hans at shalem u-boot]$ grep -R -h lcd_gpio_0 ../sunxi-boards/sys_config |
>> sort | uniq
>> ;lcd_gpio_0          = port:PA23<0><0><default><default>
>> ;lcd_gpio_0          = port:PH10<1><0><2><1>
>> Binary file ../sunxi-boards/sys_config/a20/script.bin matches
>> lcd_gpio_0      =
>> lcd_gpio_0          =
>> lcd_gpio_0 =
>> lcd_gpio_0 = ""
>> lcd_gpio_0 = port:PA06<1><0><default><1>
>> lcd_gpio_0 = port:PH07<1><0><default><1>
>> lcd_gpio_0 = port:PH10<1><0><2><1>
>>
>> Shows that the port is always put in output high mode, grepping for gpio_1
>> returns
>> 2 boards which use gpio_1 (and higher):
>>
>> sys_config/a20/icou_fatty_i.fex
>> sys_config/a31s/msi_primo81.fex
>>
>> Both of which have a non supported cpu_if setting of 4 resp 6.
>>
>> So it seems for now we can simply add a CONFIG_VIDEO_LCD_GPIO0 and always
>> drive the pin specified there (if any) high, and then we're good to go.
>
> See the previous paragraph about the name.

Although I think that it is great that you've schematics for the q8h, we do not
have schematics for the majority of the boards we want to support, so I think it
is best to stick with the CONFIG_VIDEO_LCD_GPIO# name, and add a commment to the
defconfig what it really is in the cases where we know what it is used for.

Regards,

Hans