Re: [PATCH] arm: imx: mmdc_size: Increase row_max for imx8m

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Teresa,

On 20.06.22 14:27, Teresa Remmet wrote:
> Hello Ahmad,
> 
> Am Montag, dem 20.06.2022 um 14:02 +0200 schrieb Ahmad Fatoum:
>> Hello,
>>
>> On 20.05.22 16:23, Teresa Remmet wrote:
>>> As DDRC_ADDRMAP7_ROW_B16 and DDRC_ADDRMAP7_ROW_B17 are used
>>> now for the row size calculation we need to increase row_max to 18.
>>>
>>> For LPDDR4 this only works in combination with ram timings
>>> created with recent configuration spreadsheet versions.
>>> With older versions the register DDRC_ADDRMAP7 may not be set and
>>> calculation will lead to wrong results even with this patch.
>>>
>>> Fixes: dad2b5636bd8 ("ARM: imx: Add imx8 support for 18 bit SDRAM
>>> row size handle")
>>> Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
>>
>> I have an out-of-tree i.MX8MM board with LPDDR4 that reported a
>> correct size of 1G
>> prior to this patch and now it reports 4G. DDRC_ADDRMAP7 is not
>> explicitly initialized,
>> but it's being read as zero, so the calculation seems to still be
>> broken..
> 
> yes, this is why I added the note to the commit message. The RAM
> timings of the board you are using have been created with a old version
> of the spreadsheet ( < version 19 for i.MX8MM).
> This issue is worked around when this patch is reverted as
> DDRC_ADDRMAP7 is not taken into account. But calculating big ram sizes
> will probably not work then.
> 
> I have set the DDRC_ADDRMAP7 register manually in the RAM configuration
> in such a case. As I don't see a solution that fits for all. But would
> be happy for one. :)

What would the 'neutral' value to write into this register be? zero
seems to not be it.

Thanks,
Ahmad

> 
> Regards,
> Teresa
> 
>>
>>> ---
>>>  arch/arm/mach-imx/esdctl.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm/mach-imx/esdctl.c b/arch/arm/mach-
>>> imx/esdctl.c
>>> index 8dd0ddbbc965..b070ebc62a45 100644
>>> --- a/arch/arm/mach-imx/esdctl.c
>>> +++ b/arch/arm/mach-imx/esdctl.c
>>> @@ -488,7 +488,7 @@ static resource_size_t
>>> imx8m_ddrc_sdram_size(void __iomem *ddrc)
>>>  
>>>  	return imx_ddrc_sdram_size(ddrc, addrmap,
>>>  				   12, ARRAY_AND_SIZE(col_b),
>>> -				   16, ARRAY_AND_SIZE(row_b),
>>> +				   18, ARRAY_AND_SIZE(row_b),
>>>  				   reduced_adress_space, true);
>>>  }
>>>  
>>
>>


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