AnsweredAssumed Answered

HDMI DRM custom resolution and clock frequency

Question asked by Simon Tsaoussis on Mar 27, 2020
Latest reply on Jun 23, 2020 by jackson xu

Hi,

I have been messing with a bunch of the kernel parameters for the iMX8MQ and I was curious as to how to generate values for the HDMI TX table in the kernel->drivers->GPU->DRM->iMX->HDP folder because I need a rather specific timing generated for a nonstandard HDMI input. I am looking to generate a PIX-CLK frequency of 204_800KHz.

 

(Note underscores are to keep track of decimal places and these are rewritten from impossible to read table data to something human-readable)

 

I guessed at a few values for the table as follows:

TABLE 8 Entry {
T8_PIXEL_CLK_FREQ_KHZ : 204_800,
T8_FEEDBACK_FACTOR : 1_000,
T8_DATA_RANGE_MBPS : 2_048_000,
T8_CMNDA_PLL0_IP_DIV : 0x03,
T8_CMN_REF_CLK_DIG_DIV : 0x01,
T8_REF_CLK_DIVIDER_SCALER : 0x01,
T8_PLL_FB_DIV_TOTAL : 220, ?
T8_CMNDA_PLL0_FB_DIV_LOW : 0x0AC,
T8_CMNDA_PLL0_FB_DIV_HIGH : 0x02C,
T8_PIXEL_DIV_TOTAL : 10,
T8_CMNDA_PLL0_PXDIV_LOW : 0x03,
T8_CMNDA_PLL0_PXDIV_HIGH : 0x03,
T8_VCO_FREQ_KHZ : 2_048_000,
T8_VCO_RING_SELECT : 0,
T8_CMNDA_HS_CLK_0_SEL : 1,
T8_CMNDA_HS_CLK_1_SEL : 1,
T8_HSCLK_DIV_AT_XCVR : 2,
T8_HSCLK_DIV_TX_SUB_RATE : 1,
T8_TX_CLK_KHZ : 1_024_000,
T8_CMNDA_PLL0_HS_SYM_DIV_SEL : 0x0,
T8_CMNDA_PLL0_CLK_FREQ_KHZ : 204_000,
T8_PIXEL_CLK_OUTPUT_ENABLE : 1,
T28HPC_HDMITX_CLOCK_CONTROL_TABLE_COLS_PIXEL_OUT
}

 

 &

 

TABLE9 Entry {
T9_VCO_FREQ_BIN : 25,
T9_PLL_VCO_FREQ_KHZ_MIN : 3060000,
T9_PLL_VCO_FREQ_KHZ_MAX : 3060000,
T9_VOLTAGE_TO_CURRENT_COARSE : 0x6,
T9_VOLTAGE_TO_CURRENT : 0x3,
T9_NDAC_CTRL : 0x1,
T9_PMOS_CTRL : 0x1,
T9_PTAT_NDAC_CTRL : 0x00,
T9_PLL_FEEDBACK_DIV_TOTAL : 0x07, ?
T9_CHARGE_PUMP_GAIN : 570,
T9_COARSE_CODE : 0x4C,
T9_V2I_CODE : 6,
T9_VCO_CAL_CODE : 225,
}

 

Any suggestions? Or is there a way I can talk with an application engineer?

 

I figured I'd give the forum a try before giving up on the iMX8 platform which we have spent several thousand on and move over to a platform that supports custom HDMI output readily.

 

Sincerely,

 

Simon

Outcomes