[U-Boot] [PATCH 11/14] sunxi: Fill memory before comparing it when doing dram init on sun6i

[Hans de Goede]

Hi,

On 18-12-14 20:12, Ian Campbell wrote:
> On Tue, 2014-12-16 at 21:31 +0100, Hans de Goede wrote:
>> The sun8i boot0 code fills the DRAM with a "random" pattern before comparing
>> it at different offsets to do columns, etc. detection. The sun6i boot0 code
>> does not do it, but it seems like a good idea to do this regardless.
>
> Is this the right way round?

Yes, while working on the sun8i code I noticed that it was prefilling memory
before doing wrap-around checks like the sun6i code is doing too, and then I
realized that the sun6i code was relying on whatever is in DRAM being random
enough for its wrap-around tests to work, without ensuring it is random
enough.

> The existing sun6i code (which you are
> moving here) seems to _rely_ on something having written a useful
> pattern, which I would have assumed to have been boot0. Or else how does
> it work now? Chance?

Yep, it purely works by chance so far.

Regards,

Hans


>
>> The new mctl_mem_fill function this introduces is added as an inline helper
>> in dram.h, so that it can be shared with the sun8i dram code.
>>
>> While at it move mctl_mem_matches to dram.h for re-use in sun8i too.
>>
>> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
>> ---
>>   arch/arm/cpu/armv7/sunxi/dram_sun6i.c  | 15 +--------------
>>   arch/arm/include/asm/arch-sunxi/dram.h | 29 +++++++++++++++++++++++++++++
>>   2 files changed, 30 insertions(+), 14 deletions(-)
>>
>> diff --git a/arch/arm/cpu/armv7/sunxi/dram_sun6i.c b/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
>> index e1670e5..4675c48 100644
>> --- a/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
>> +++ b/arch/arm/cpu/armv7/sunxi/dram_sun6i.c
>> @@ -326,20 +326,6 @@ static void mctl_port_cfg(void)
>>   	writel(0x00000307, &mctl_com->mbagcr[5]);
>>   }
>>
>> -static bool mctl_mem_matches(u32 offset)
>> -{
>> -	const int match_count = 64;
>> -	int i, matches = 0;
>> -
>> -	for (i = 0; i < match_count; i++) {
>> -		if (readl(CONFIG_SYS_SDRAM_BASE + i * 4) ==
>> -		    readl(CONFIG_SYS_SDRAM_BASE + offset + i * 4))
>> -			matches++;
>> -	}
>> -
>> -	return matches == match_count;
>> -}
>> -
>>   unsigned long sunxi_dram_init(void)
>>   {
>>   	struct sunxi_mctl_com_reg * const mctl_com =
>> @@ -391,6 +377,7 @@ unsigned long sunxi_dram_init(void)
>>   		    MCTL_CR_BANK(1) | MCTL_CR_RANK(1));
>>
>>   	/* Detect and set page size */
>> +	mctl_mem_fill();
>>   	for (columns = 7; columns < 20; columns++) {
>>   		if (mctl_mem_matches(1 << columns))
>>   			break;
>> diff --git a/arch/arm/include/asm/arch-sunxi/dram.h b/arch/arm/include/asm/arch-sunxi/dram.h
>> index 18924f5..0bf718c 100644
>> --- a/arch/arm/include/asm/arch-sunxi/dram.h
>> +++ b/arch/arm/include/asm/arch-sunxi/dram.h
>> @@ -22,6 +22,8 @@
>>   #include <asm/arch/dram_sun4i.h>
>>   #endif
>>
>> +#define MCTL_MEM_FILL_MATCH_COUNT 64
>> +
>>   unsigned long sunxi_dram_init(void);
>>
>>   /*
>> @@ -37,4 +39,31 @@ static inline void mctl_await_completion(u32 *reg, u32 mask, u32 val)
>>   	}
>>   }
>>
>> +/*
>> + * Fill beginning of DRAM with "random" data for mctl_mem_matches()
>> + */
>> +static inline void mctl_mem_fill(void)
>> +{
>> +	int i;
>> +
>> +	for (i = 0; i < MCTL_MEM_FILL_MATCH_COUNT; i++)
>> +		writel(0xaa55aa55 + i, CONFIG_SYS_SDRAM_BASE + i * 4);
>> +}
>> +
>> +/*
>> + * Test if memory at offset offset matches memory at begin of DRAM
>> + */
>> +static inline bool mctl_mem_matches(u32 offset)
>> +{
>> +	int i, matches = 0;
>> +
>> +	for (i = 0; i < MCTL_MEM_FILL_MATCH_COUNT; i++) {
>> +		if (readl(CONFIG_SYS_SDRAM_BASE + i * 4) ==
>> +		    readl(CONFIG_SYS_SDRAM_BASE + offset + i * 4))
>> +			matches++;
>> +	}
>> +
>> +	return matches == MCTL_MEM_FILL_MATCH_COUNT;
>> +}
>> +
>>   #endif /* _SUNXI_DRAM_H */
>
>