[U-Boot] [PATCH] sunxi: Fix sun5i mbus speed when booting old kernels

[Hans de Goede]

Hi,

On 20-02-15 09:15, Siarhei Siamashka wrote:
> On Thu, 19 Feb 2015 14:59:16 +0100
> Hans de Goede <hdegoede at redhat.com> wrote:
>
>> Older linux-sunxi-3.4 kernels override our PLL6 setting with 300 MHz,
>> halving the mbus frequency, so set it to 300 MHz ourselves and base the
>> mbus divider on that.
>>
>> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
>> ---
>>   arch/arm/include/asm/arch-sunxi/clock_sun4i.h | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/arch/arm/include/asm/arch-sunxi/clock_sun4i.h b/arch/arm/include/asm/arch-sunxi/clock_sun4i.h
>> index d297ed0..c28ee05 100644
>> --- a/arch/arm/include/asm/arch-sunxi/clock_sun4i.h
>> +++ b/arch/arm/include/asm/arch-sunxi/clock_sun4i.h
>> @@ -144,7 +144,16 @@ struct sunxi_ccm_reg {
>>
>>   #define PLL1_CFG_DEFAULT	0xa1005000
>>
>> +#if defined CONFIG_OLD_SUNXI_KERNEL_COMPAT && defined CONFIG_MACH_SUN5I
>> +/*
>> + * Older linux-sunxi-3.4 kernels override our PLL6 setting with 300 MHz,
>> + * halving the mbus frequency, so set it to 300 MHz ourselves and base the
>> + * mbus divider on that.
>> + */
>> +#define PLL6_CFG_DEFAULT	0xa1009900
>> +#else
>>   #define PLL6_CFG_DEFAULT	0xa1009911
>> +#endif
>>
>>   /* nand clock */
>>   #define NAND_CLK_SRC_OSC24		0
>
> Are there any good reasons to use 600MHz instead of 300MHz for PLL6 in
> the default u-boot build?
>
> Maybe PLL6 can be just set to 300MHz for sun5i in all cases, regardless
> of the CONFIG_OLD_SUNXI_KERNEL_COMPAT define?

Basically the reasons are the same as why you want to keep PLL5 running
at a high speed, PLL6 is a potential parent PLL for all mod0 clk using
peripherals, and having it higher gives us more possible clocks.

I agree that this (and the PLL5 speed) are an issue we need a better fix
for then CONFIG_OLD_SUNXI_KERNEL_COMPAT if at all possible.

I'll discuss this further as a reply to your:
"[PATCH] sunxi: Machine id hack to prevent loading buggy sunxi-3.4 kernels"
mail.

Regards,

Hans