Hi all,
Recently, I have been debugging the "Synchronous Exception" issue in
UEFI. This issue is very strange.If I used the Hisilicon bootloader and
1.3 ATF to launching UEFI,the UEFI could be booted successfully without
any issues.But if I used the "l-loader" and 1.3ATF on github to boot
UEFI, it would arose a "Synchronous Exception" issue accidentally in
FaultTolerantWriteDxe driver in UEFI. That means,with the same
"l-loader" boot image on github, sometimes we can launching the UEFI
successfully,and sometimes we will get into "Synchronous Exception" in
UEFI. And sometimes before exit from the FaultTolerantWriteInitialize
function,UEFI will get into "Synchronous Exception".
I debugged this issue for several days,and finally I found that,in front
of the "problematic code",there are some "BlockIo" functions in
BlockVariableDxe driver which have some relations with the "Synchronous
Exception". If the "BlockIo" functions can read and write the EMMC
correctly,the UEFI can get into OS loader and boot the kernel
successfully without any issues;But sometimes the "BlockIo" functions
can't work "really". That means,when we use these functions,we can't
make sure these functions have operated the EMMC rightly or not,even
though these BlockIo functions return success after being executed. I
used the BlockRead function to read one block from the EMMC to a Buffer,
sometimes I can get the right value in the Buffer,but sometimes they are
all zero or wrong data.
When the BlockRead can't "really" read data from EMMC,the UEFI will get
into "Synchronous Exception" in FaultTolerantWriteDxe driver.
I think it is the issue of EMMC which led to the "Synchronous Exception"
in UEFI. The "Hiboot" is a full function bootloader,it will initialize
the EMMC when we power on the system. But the "l-loader" and 1.3 ATF(not
include BL33) didn't initialize the EMMC .
I'm not sure about the relationship between BlockIo function in UEFI and
EMMC initialization in previous loader. Does UEFI rely on the eMMC being
initialized by previous loader? As we know,the BlockIo functions are the
system function supplied by UEFI,and do you know which factors will
influence their functionality? Can you give me some advises about this
issue?
Thanks very much!
Best regards,
Wengang
