Re: [PATCH v6 2/3] media: i2c: adv748x: add adv748x driver
From: Kieran Bingham
Date: Mon Jul 03 2017 - 11:01:01 EST
On 03/07/17 15:45, Kieran Bingham wrote:
> Hi Hans,
> Thanks for your review,
> On 03/07/17 14:51, Hans Verkuil wrote:
>> On 06/27/2017 05:03 PM, Kieran Bingham wrote:
>>> From: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
>>> Provide support for the ADV7481 and ADV7482.
>>> +/* -----------------------------------------------------------------------------
>>> + * HDMI and CP
>>> + */
>>> +#define ADV748X_HDMI_MIN_WIDTH 640
>>> +#define ADV748X_HDMI_MAX_WIDTH 1920
>>> +#define ADV748X_HDMI_MIN_HEIGHT 480
>>> +#define ADV748X_HDMI_MAX_HEIGHT 1200
>>> +#define ADV748X_HDMI_MIN_PIXELCLOCK 0 /* unknown */
>> 0 makes no sense. Something like 13000000 would work better (pixelclock rate for
>> V4L2_DV_BT_CEA_720X480I59_94 is 13500000).
> This is another one that must have got lost somehow - you'd already told me this
> and I'm really sure I changed it to the value you suggested ...
> /me is confused at code loss - Must have been a rebase gone bad. :-(
>>> +#define ADV748X_HDMI_MAX_PIXELCLOCK 162000000
>> You probably based that on the 1600x1200p60 format?
> No idea I'm afraid - it's the value that was set when I recieved the driver...
>> 162MHz is a bit low for an adv receiver. The adv7604 and adv8742 have a max rate
>> of 225 MHz.
>> This should be documented in the datasheet.
> Hrm ... haven't found it yet - I'll keep digging....
I've found this as the most relevant reference:
The ADV7481 HDMI capable receiver supports a maximum pixel clock frequency of
162 MHz, allowing HDTV formats up to 1080p, and display resolutions up to UXGA
(1600 Ã 1200 at 60 Hz). The device integrates a consumer electronics control
(CEC) controller that supports the capability discovery and control (CDC)
feature. The HDMI input port has dedicated 5 V detect and Hot PlugTM assert pins.
So that certainly looks like 162 MHz is the correct value.
>> Besides, you need a bit of margin since detected pixelclock rates can be a bit off.
Does that mean you would you recommend adding 0.5 MHz to the 162 MHz in a
similar way as the minimum, or keep at 162 MHz ?
(I'm assuming stay at 162 MHz, as the 7604 is set at 225MHz)