AM335x LCD screen flickering

Priyanka P

Other Parts Discussed in Thread: AM3352

We have a custom board that uses AM3352 processor. In revision A, we used 1.0 silicon version and in revision B, 2.1 silicon version. In Revision B boards, we are seeing LCD flickering problem with LCDC sync lost prints but not in Revision A. Expect silicon version we have not done any changes in recent revision.

When we probed LCD pclk and sync signals, we observe PCLK signal going low causing changes on sync signals. If you have any recent patches to fix this issue, could you give details about it. Please, Suggest solution for this issue.

Thanks

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

Hi,

What software and which version are you using?

0 Priyanka P over 10 years ago in reply to Biser Gatchev-XID

Prodigy 70 points

Kernel: linux-3.2.0-psp04.06.00.11

Android: Jelly bean 4.2.2

0 Priyanka P over 10 years ago in reply to Priyanka P

Prodigy 70 points

We are using DDR3L part(MT41K256M16HA-125 M:E) interfaced with AM3352.

DDR self refresh time PM registers

0x4c000038 : 0x2a0

0x4c00003c(shadow) : 0xa0

When we set 0x00 for these two registers, we are not observing LCD flickering even single time but this change affect suspend resume cycle. Suspend is happening but even single time the system is not resuming.

We tried to change the reg_sr_tim settings , but LCD flickering continues.

How DDR self refresh time and LCD flickering are related? Is there any fix for this issue?

0 Biser Gatchev-XID over 10 years ago in reply to Priyanka P

TI__Guru**** 393215 points

If you observe this effect under Android you should turn to the Android forum: http://e2e.ti.com/support/embedded/android/f/509.aspx

0 sadasivappa s over 9 years ago in reply to Biser Gatchev-XID

Intellectual 460 points

Hi Biser,

I think this is not related to Android framework, something related to Display controller. why the Pixel clock goes down abruptly. This is happening only with AM3352 SOC 2.1 version. Do you have any fix are workaround in this regard.

Our production is halted due to to this issue.

Best regards
Sadasivappa

0 Biser Gatchev-XID over 9 years ago in reply to sadasivappa s

TI__Guru**** 393215 points

So far we haven't heard of a similar issue from customers. Have you checked if the screen is not being blanked as described here: http://processors.wiki.ti.com/index.php/AM335x_LCD_Controller_Driver's_Guide#Usage_and_Verification

0 Biser Gatchev-XID over 9 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Also please describe what do you mean by "lcd clock signal going low"?

0 sadasivappa s over 9 years ago in reply to Biser Gatchev-XID

Intellectual 460 points

Hi Biser,

In Board with screen flickers, it is observed that PCLK will go low. Also HSYNC will be low for the same duration. VSYNC frequency varies upto 250Hz instead of being around 55 to 60Hz.

We also tried with below Post, where the flickering stops but we are not able to suspend and resume the device for power management purpose.

e2e.ti.com/.../292766

Is there any limitations in AM3352 SOC of version 2.1 regarding Display controller?

Mean while i will check the blanking as you suggested.

Best regards
Sadasivappa

0 Biser Gatchev-XID over 9 years ago in reply to sadasivappa s

TI__Guru**** 393215 points

There is no Errata in Rev.2.1 silicon regarding the LCD controller. The only limitation is that the LCD functional (input) clock must not be above 200MHz. Can you dump the following registers with the devmem2 tool:

LCD_CTRL 0x4830E004

CM_CLKMODE_DPLL_DISP 0x44E00498

CM_CLKSEL_DPLL_DISP 0x44E00454

CM_DIV_M2 0x44E004A4

CLKSEL_LCDC_PIXEL_CLK 0x44E00534

0 sadasivappa s over 9 years ago in reply to Biser Gatchev-XID

Intellectual 460 points

Hi Biser,

Below is the values of register dump:

LCD_CTRL 0x4830E004 = 0x00002E01

CM_CLKMODE_DPLL_DISP 0x44E00498 = 0x00000007

CM_CLKSEL_DPLL_DISP 0x44E00454 = 0x00001901

CM_DIV_M2 0x44E004A4 = 0x00000201

CLKSEL_LCDC_PIXEL_CLK 0x44E00534 = 0x00000000

Best Regards

Sadasivappa

0 Biser Gatchev-XID over 9 years ago in reply to sadasivappa s

TI__Guru**** 393215 points

OK, here is what you have currently:

LCD functional clock source is Display PLL, which is enabled and locked. Display PLL values are M=25, N=1, M2=1. I think you are running from a 24MHz main oscillator, so:

LCD functional clock = (24MHz *25 / (1 + 1)) / 1 = 300MHz and this is absolutely incorrect. Maximum value for this clock must be 200MHz.

After that pixel clock divisor is 46, so:

LCD pixel clock = 300MHz / 46 = 6.52MHz

I suggest you take a look at this post http://e2e.ti.com/support/arm/sitara_arm/f/791/p/398415/1408503#1408503 SDK 6.0 has a bug in the Display PLL calculations.

0 sadasivappa s over 9 years ago in reply to Biser Gatchev-XID

Intellectual 460 points

Hi Biser,

Following are the values after Changing the funcitonal clock value to 200MHz

LCD_CTRL 0x4830E004 = 0x00001E01

CM_CLKMODE_DPLL_DISP 0x44E00498 = 0x00000007

CM_CLKSEL_DPLL_DISP 0x44E00454 = 0x00001902

CM_DIV_M2 0x44E004A4 = 0x00000201

CLKSEL_LCDC_PIXEL_CLK 0x44E00534 = 0x00000000

But still the LCD flickering exists.

Best Regards

Sadasivappa

0 Biser Gatchev-XID over 9 years ago in reply to sadasivappa s

TI__Guru**** 393215 points

Then this eliminates the clock frequencies. You will need to debug this further. Could this be caused by a display buffer underflow? Sorry, but I don't have the SW expertise to help on that.

0 sadasivappa s over 9 years ago in reply to Biser Gatchev-XID

Intellectual 460 points

Hi Biser,

This is happening due to LCD sync Lost. I don't know why this happens only in some of the boards. 50% of the boards have this problem.

Best Regards
Sadasivappa

0 Biser Gatchev-XID over 9 years ago in reply to sadasivappa s

TI__Guru**** 393215 points

Have you checked if AM335X Errata 1.0.30 does not cause this problem?

0 sadasivappa s over 9 years ago in reply to Biser Gatchev-XID

Intellectual 460 points

Yes, We took care of all issues that listed in Errata. There is no noise generated from any of the components or circuit.

All RevA boards with AM3352 (rev 1.0) works fine without any issues. But RevB boards with AM3352(rev 2.1) produce flickering in 5 out of 10 boards. Only different in RevB from RevA is power management is enabled (Suspend/Resume).

Best Regards
Sadasivappa

0 Biser Gatchev-XID over 9 years ago in reply to sadasivappa s

TI__Guru**** 393215 points

Do you see the same issue with PM disabled?

0 sadasivappa s over 9 years ago in reply to Biser Gatchev-XID

Intellectual 460 points

Even after PM disabled flickering exists.

Best Regards
Biser

0 Biser Gatchev-XID over 9 years ago in reply to sadasivappa s

TI__Guru**** 393215 points

Have you eliminated PCB design/manufacturing as root issue? This begins to sound like a hardware problem...

0 CM_ over 9 years ago in reply to Biser Gatchev-XID

Prodigy 190 points

This problem has been encountered by at least two other customers:
My post here (at the bottom of the post): http://e2e.ti.com/support/embedded/android/f/509/p/385712/1371982#1371982
and another one here: http://e2e.ti.com/support/embedded/android/f/509/p/292766/1153561#1153561

I've posted a possible workaround in the thread at the second link, maybe this will help you.
In short terms: Enable self refresh right before you enter the sleep mode. Disable self refresh on sleep mode exit.

0 sadasivappa s over 9 years ago in reply to CM_

Intellectual 460 points

Hi CM_,

If we disable the self refresh mode, is this causes any side effects when the device is in operation?

Best Regards

Sadasivappa

0 CM_ over 9 years ago in reply to sadasivappa s

Prodigy 190 points

I use this workaround myself and as far as I understand, it should not cause any side effects.

0 durai samy over 9 years ago in reply to Biser Gatchev-XID

Intellectual 515 points

Hi Biser,

We have custom board powered by AM3352 processor with 8 inch LCD display. Our customer wants to displays the Logo in Uboot loader itself hence configuring the raster controller in Uboot. We are facing the pixel clock configuration issue, measured with scope it shows that 8 Mhz but we are expecting the 65 Mhz.

Please find the below registers configuration values,

0x4830e004 = 0x301;
0x44e00498 = 0x4;
0x44e00454= 0x1902;
0x44e004a4= 0x201;
0x44e00534= 0x0;

LCD Pixel clock = 200 Mhz /3 =66 Mhz.

In oscilloscope it shows that 8 Mhz.

Am I missing anything?

Note: After booting Linux Pixel clock are correctly measuring as expected ( 65 Mhz )

Please help on this.

Thanks
Durai

0 sadasivappa s over 9 years ago in reply to CM_

Intellectual 460 points

Hi

Thanks Guys, This worked for us.

Regards
Sadasivappa

0 Filosofi over 8 years ago in reply to durai samy

Intellectual 925 points

Hi Durai,

I'm having the very same problem you had.

Could you give me a hint ?

Thank you very much,

Gabriele

0 durai samy over 8 years ago in reply to Filosofi

Intellectual 515 points

Hi Filosofi,

Follow the below instruction for Splash screen display in Uboot boot up

1. Download the StaterWare from TI site from here: software-dl.ti.com/.../index_FDS.html

2. Install it;

2. Go to instalation directory and find /tools/bmpToRaster;

3. Go to the header file BitmapReader.h and comment out #define COMPRESS.

4. To get the binary do make command;

5. Prepare the image with exactly size of display, in my case the image is horizontal with 480x800 pixels and 24bpp. The file name is image.bmp;

6. Put the image file on /tools;

7. give the command: ./a.out 800 480 ./imagem.bmp ./image.h 24 RGB;

8. The file image.h will be created;

9. Edit this file with this:

#ifndef CONFIG_SPL_BUILD
unsigned int const image1[] __attribute__((aligned(4)))= {

....

#endif

10. Copy /lcd directory to /u-boot/drivers 4578.lcd.tar.gz

11. In /u-boot/Makefile add the red line:

LIBS = post/libpost.o
LIBS = drivers/lcd/liblcd.o

ifeq ($(SOC),ti81xx)
LIBS = $(CPUDIR)/omap-common/libomap-common.o
endif

12. At /uboot/include/configs/am335x_evm.h add the lines bellow just before the file end:

/* LCD Support */
#define CONFIG_LCD_TCM

13. At /u-boot/board/ti/am335x/evm.c add the red line inside board_init(void):

...

#ifndef CONFIG_SPL_BUILD
    board_evm_init();

    Lcd_Init(); // Initialize
#endif

....

    gpmc_init();

Recompile uboot and save the MLO and u-boot.img files at SDcard using the correct tools and boot the system. The image will appear until Android get the lcd control.

Note: We red the all PLL settings from Linux code by using devmem tool and updated in Uboot.

+*(volatile unsigned int *)0x4830e004= 0x00000201;
+*(volatile unsigned int *)0x4830e00c= 0x00000000;
+*(volatile unsigned int *)0x4830e010= 0x00440044;
+*(volatile unsigned int *)0x4830e014= 0x00000000;
+*(volatile unsigned int *)0x4830e018= 0x00000000;
+*(volatile unsigned int *)0x4830e01c= 0x00440044;
+*(volatile unsigned int *)0x4830e020= 0x00000000;
+*(volatile unsigned int *)0x4830e024= 0x00000000;
+*(volatile unsigned int *)0x4830e028= 0x06200081;
+*(volatile unsigned int *)0x4830e02c= 0x773bbbf0;
+*(volatile unsigned int *)0x4830e030= 0x0c0a2eff;
+*(volatile unsigned int *)0x4830e034= 0x02300000;
+*(volatile unsigned int *)0x4830e038= 0x00000000;
+*(volatile unsigned int *)0x4830e03c= 0x00000000;
+*(volatile unsigned int *)0x4830e040= 0x00000041;
+*(volatile unsigned int *)0x4830e044= 0xae100000;
+*(volatile unsigned int *)0x4830e048= 0xae3ffffc;
+*(volatile unsigned int *)0x4830e04c= 0xae100000;
+*(volatile unsigned int *)0x4830e050= 0xae3fffff;
+*(volatile unsigned int *)0x4830e054= 0x00000014;
+//*(volatile unsigned int *)0x4830e058=
+//*(volatile unsigned int *)0x4830e05c=
+*(volatile unsigned int *)0x4830e060= 0x00000325;
+*(volatile unsigned int *)0x4830e064= 0x00000325;
+*(volatile unsigned int *)0x4830e06c= 0x00000007;
+*(volatile unsigned int *)0x4830e070= 0x00000000;

Regards

Durai

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AM335x LCD screen flickering