????DDR??????????????????Uboot?м??????
?????? U-Boot?У?Denx??U-Boot????????????????DDR?????????????????????????????ü???????????????裺????????????????DDR????洢??????????漰???????????????????????????DDR??????????????????????????debug???????????Denx????? DDR?????????????????????????????о????

??????????????????????·??????
????1????????????????
?????????????????????????????????????????????????????????????????????????????洢??????????壬?????????????????λ????????testing sequence????????????????????????????????????????
????2????????????????
???????????????????????????????????????????????????????????·??
????3????μ????????????????
????Denx ???????????????????Tricky????????????????????????????????????????????????д?????????pattern=0b01??0b???????????????????ж?????????·????????????????????????????????????????????64λ??????????pattern = 0b101010101010101010.... ????????λ??????????????????????????????????????????饗????????????pattern???????????????????????????????????????ж?·??????????pattern???? 0b110011001100...... ???????????4???????????飬8???????飬???????6??pattern??????? 0xaaaaaaaaaaaaaaaa??0xcccccccccccccccc??0xf0f0f0f0f0f0f0f0??0xff00ff00ff00ff00??0xffff0000ffff0000??0xffffffff00000000???????д????????6??pattern?????????????????????·????
????4????μ??????????????????????????·???·
?????????6??paatern????????12??pattern??????λ??????д??????0??1??
????5??????floating buses????
????floating buses??“???”???????????????????д?????????????????д????????????????????磬??????????????????????????????????????????????д????????????????????????·???
????6????μ?????????floating buses????
???????floating buses????????????????д????????????????ζ??????д??????????????磬Xд??X1λ???Yд??Y1λ??????X1λ?????X?????floating buses?????????
????7???????????
??????????????????????????????е????????λ????????????洢λ?á????????????д???λ???“???”???????λ?á?
????8?????????????
????????????????????????????
????1???????????????????д????????????????????? (addr) = addr??????????д?????????????????????????λ???????????
????2???????ν??????????????????????????flip/toggle???????????????????????????????????????????????λ???????????
????????????????????????????????????????Ч??
????9???洢????????
???????????????????????????????????????????洢?????????????????DDR???о????????о????????????bit-stuck??????????????????0??????1???????1??????0????????????????ò????pattern?д?????????е???????????????Щ????? pattern??0x5555?? 0xAAAA???
????10????????????DDR????????
?????????DDR????????????棬????????????????????ü???С?????Uboot??????????м??????????????????????????????????
????1????mtest addr lenth pattern
?????????????????DDR??Uboot??????????0?????????uboot????????????0x10000000?????????Щ???????????????????????
????2????????NOR flash???????????У??? cp.b 0x20080000 0x7fc0 20000??????? cmp.b 0x20080000 0x7fc0 20000??
????3????????kernel image??????У?copy NOR flash ??tftp???У???????iminfo LOAD_ADDR ???CRC????
?????????????????????pattern??DDR????п?????????????????????Pattern???????????Щ??
???????????????????????????Linux??????????????????????????????λ????