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SDXC support on AM335x+linux platform

Yaoming Qin
Expert 3280 points

Hi, all

    My customer want to confirm whether AM335x+linux platform can support SDXC or not. I checked the commits in Linux kernel tree, found that there is a commit talking about SXDC as following, so can anyone help me to confirm it ?

commit f2815f68dabbb373fd1c9f0fd4a609d486697c2b
Author: Subhash Jadavani <subhashj@codeaurora.org>
Date:   Wed Aug 10 11:16:01 2011 +0530

    mmc: sd: Handle SD3.0 cards not supporting UHS-I bus speed mode
    
    Here is Essential conditions to indicate Version 3.00 Card
    (SD_SPEC=2 and SD_SPEC3=1) :
    (1) The card shall support CMD6
    (2) The card shall support CMD8
    (3) The card shall support CMD42
    (4) User area capacity shall be up to 2GB (SDSC) or 32GB (SDHC)
        User area capacity shall be more than or equal to 32GB and
        up to 2TB (SDXC)
    (5) Speed Class shall be supported (SDHC or SDXC)
    
    So even if SD card doesn't support any of the newly defined
    UHS-I bus speed mode, it can advertise itself as SD3.0 cards
    as long as it supports all the essential conditions of
    SD3.0 cards. Given this, these type of cards should atleast
    run in High Speed mode @50MHZ if it supports HS.


    But current initialization sequence for SD3.0 cards is
    such that these non-UHS-I SD3.0 cards runs in Default
    Speed mode @25MHz.
    
    This patch makes sure that these non-UHS-I SD3.0 cards run
    in High Speed Mode @50MHz.
    
    Tested this patch with SanDisk Extreme SDHC 8GB Class 10 card.

								


				
				

				
			

		

			
						
									
                			    			                        
						
						
			
			
						
			                        
			
			
				
			  
			

			     
			

		


				    			

				
    
					
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