[U-Boot] [PATCH] ARM: socfpga: Assure correct ACTLR configuration

[Marek Vasut]

On 05/31/2018 11:52 AM, See, Chin Liang wrote:
> On Tue, 2018-05-29 at 18:39 +0200, Marek Vasut wrote:
>> Make sure the ARM ACTLR register has correct configuration, otherwise
>> the Linux kernel refuses to boot. In particular, the "Write Full Line
>> of Zeroes" bit must be cleared.
>>
>> Signed-off-by: Marek Vasut <marex at denx.de>
>> Cc: Chin Liang See <chin.liang.see at intel.com>
>> Cc: Dinh Nguyen <dinguyen at kernel.org>
>> ---
>> NOTE: This gem was well hidden in the Altera U-Boot fork and is
>> really needed.
>>       What is not entirely clear to me is WHY ? So why is this needed
>> ?
> 
> I vaguely recall it's related to HW constrain. And check back the
> downstream U-Boot, actually we need to set the bit instead clearing
> it. https://github.com/altera-opensource/u-boot-socfpga/blob/socfpga_v2
> 014.10_arria10_bringup/arch/arm/cpu/armv7/socfpga_arria10/pl310.c

You are clearing it here:
https://github.com/altera-opensource/u-boot-socfpga/blob/socfpga_v2014.10_arria10_bringup/arch/arm/cpu/armv7/socfpga_arria10/lowlevel_init.S#L35

The PL310 configuration is a different register. What HW constraint ?
I'd really like to understand this problem.

-- 
Best regards,
Marek Vasut