[U-Boot-Users] Regarding Dcache Flush in MPC85xx

[Fowley, Douglas G (GE Infra, Energy)]

> Date: Tue, 26 Feb 2008 23:00:17 +0530
> From: "s.balamurugan" <s.balamurugan at gdatech.co.in>
> Subject: [U-Boot-Users] Regarding Dcache Flush in MPC85xx
> To: u-boot-users at lists.sourceforge.net
> Message-ID: <47C44CA9.6010906 at gdatech.co.in>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> Hi,
> We are using MPC8555 processor and uboot 1.1.4 both the uboot 
> and linux 
> was up. Now we plan to port QNX, we are facing following issues.
> 
> 1. Qnx is not jumping to the startup location.  After giving 
> go command 
> control is still in the uboot only.
> 
> 2.  When searching in the mailling list we came to know qnx 
> required to 
> flush the Data Cache before disabling it in the uboot level 
> (common/cmd_bootelf.c line no:59)
> 
> 3.  I checked other powerpc architecture like 7xx/74xx, 86xx and 4xx. 
> These architecture  has seperate cache.S file ( 
> cpu/mpc86xx/cache.S). That
> file contains flush_data_cache function to flush the cache before 
> disabling it. But in the MPC85xx flushing the data cache was missing.
> 
> 4. This is a bug in the 85xx uboot code. Is there any work 
> arround for 
> this?
> 
> Thanks and Regards
> S.Balamurugan
> 

Hi S.Balamurugan,

I've worked around U-Boot's data cache issue when booting to QNX in a
couple of ways:

1. Configure the cache commands into U-Boot and run the "dcache off"
command before jumping to QNX, or
2. Add code to the QNX startup module that turns off & unlocks the data
cache.

Contact me directly if you want help with #2.

Regards,

Doug