[U-Boot-Users] Can CPU write video memory directly?

[U-Boot-Users] Can CPU write video memory directly?

[zhanglei459]

Hi all,
      Now I am debugging video chip MB86297A.Reference to hardware manual,I
have configured PCI registers ,Carmine Control registers and DRAM Control
registers under U-boot , other modules registers have not been configured.I
dont know how to verify DRAM is configured correctly. When I "md" video
memory,they are all zero,and after I "mm" video memory,they are "md" still
display all zero .Are DRAM Control registers configured wrong? Does CPU
modify video memory?
    Thanks!
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[U-Boot-Users] Can CPU write video memory directly?

[Detlev Zundel]

Hi Zhanglei459,

>       Now I am debugging video chip MB86297A.Reference to hardware manual,I
> have configured PCI registers ,Carmine Control registers and DRAM Control
> registers under U-boot , other modules registers have not been configured.I
> dont know how to verify DRAM is configured correctly. When I "md" video
> memory,they are all zero,and after I "mm" video memory,they are "md" still
> display all zero .

Something must be wrong in your configuration.  I recently did a
standard "mtest" on a CoralP attached graphics memory *after* correctly
setting up the CoralP control registers.  Note that I had to setup CCF
and MMR registers correctly (swapping endinanness by hand!).

> Are DRAM Control registers configured wrong? 

Most likely.

> Does CPU modify video memory?

No, why should it?

Cheers
  Detlev

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