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Original question:

AM62L: dsi_p_clk has no rate

AM62L: dsi_sys_clk cannot be divided to produce the clock set by the screen parameters

ling ye
Prodigy 20 points
Part Number: AM62L

Tool/software:

Hi，TI expert，

We designed our products using AM62L, and now we have a problem.We are integrating a DSI panel (using a Himax hx8394 bridge chip) to the DSI output of an AM62L.

We used the screen parameters recommended in the screen data sheet and the parameters verified on other platforms, but the screen could not light up on the AM62L.

We finally found that it might be a clock problem, so I set the screen clock to 28570, which is the clock I saw some customers use to light up the screen.  RE: AM62L: dsi_p_clk has no rate 

.hdisplay    = 720,
    .hsync_start = 720 + 20,
    .hsync_end   = 720 + 20 + 20,
    .htotal      = 720 + 20 + 20 + 20,
    .vdisplay    = 1280,
    .vsync_start = 1280 + 12,
    .vsync_end   = 1280 + 12 + 10,
    .vtotal      = 1280 + 12 + 10 + 10,
    .clock       = 28570,
    .flags       = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
    .width_mm    = 68,
    .height_mm   = 136,

Then I can light up my screen, but it is not stable because the frame rate is only around 28 fps，The following is the display and terminal information：




  



So I think it is because dsi_sys_clk cannot divide the clock required by the screen， 


Can you guide me how to do it?
Or is my situation caused by some other problem?


Thanks,
Ling

























								


				
				

				
			

		

			
						
									
                			    			                        
						
						
			
			
						
			                        
			
			
				
			  
			

			     
			

		


				    			

						
















	

	

					
    
	
    





		
	
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                          TI__Expert
                        8800 points
                      
    
                          
                   		
		
    
					
    Hi,
    1. To understand correctly, with the same porch values, when you use .clock=28570 it works, but it does not work with .clock=60933 or .clock=60934?
    2. Is it possible for you to share panel part number and datasheet?
    3. To confirm fps, can you please run 'kmstest --flip' for both 28.57MHz and 60.9MHz clock?
    4. One thing to try out:

    Compute fbdiv = (h_tot * v_tot * fps * 24 / num_lanes) * 2 * opdiv * ipdiv / ref_clock
    opdiv and ipdiv cn be found in cdns-dphy.c and ref_clock is the clock you are using in your EVM (ref_clock is 25000000 for TI AM62L EVM).

    Try to adjust your porches such that fbdiv comes out to be an integral value.
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                 	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
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						in reply to Divyansh Mittal
					
									
    
	
    
	                                    
                      
    
                        
                          Prodigy
                        20 points
                      
    
                          
                   		
		
    
					
    HI，Mittal,
    

    I'm glad to have your support.
    

    

    1,Yes, with the same porch values, when you use .clock=28570 it works, but it does not work with .clock=60933.
    

    

    .hdisplay    = 720,
    

        .hsync_start = 720 + 20,
    

        .hsync_end   = 720 + 20 + 20,
    

        .htotal      = 720 + 20 + 20 + 20,
    

        .vdisplay    = 1280,
    

        .vsync_start = 1280 + 12,
    

        .vsync_end   = 1280 + 12 + 10,
    

        .vtotal      = 1280 + 12 + 10 + 10,
    

        .clock       = 28570,        //28fps
    

        //.clock         = 60933,    //60fps
    

        .flags       = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
    

        .width_mm    = 68,
    

        .height_mm   = 136,
    

    2,Of course，But see like there is no such function to send data sheet here.
    

    3，With 60MHz clock,There nothing in display.
    

     
    

      With 28MHz ,There  some test picture is displayed on the screen.
    

     
    

     
    

    4,I'll try it to see if it works.
    

    

    Or do have any suggestons for making the screen run at 60fps?
    

    

    Thank you 
    

    

    

    

    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
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						in reply to ling ye
					
									
    
	
    
	                                    
                      
    
                        
                          TI__Expert
                        8800 points
                      
    
                          
                   		
		
    
					
    ling ye said:
    2,Of course，But see like there is no such function to send data sheet here.
    

    You may just drag and drop the pdf in the box. It will create thumbnail/link. Please share the datasheet only if it is not proprietary.
    

    ling ye said:
    Or do have any suggestons for making the screen run at 60fps?
    

    Another suggestion would be to increase the all porches gradually to see if you are able to achieve better fps. Customers usually have had success in the past by increasing the porches.
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                 	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
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