linux-kernel - Re: [PATCH v1 2/4] ARM: tegra: Fix DRAM refresh-interval clobbering on resume from LP1 on Tegra30

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Message-ID: <2b3bf920-b8e1-c8c5-11cd-5a7443eda521@nvidia.com>
Date:   Tue, 20 Nov 2018 10:25:50 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>
CC:     <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 2/4] ARM: tegra: Fix DRAM refresh-interval clobbering
 on resume from LP1 on Tegra30


On 19/11/2018 22:09, Dmitry Osipenko wrote:
> On 20.11.2018 0:34, Jon Hunter wrote:
>>
>> On 30/08/2018 19:54, Dmitry Osipenko wrote:
>>> The DRAM refresh-interval is getting erroneously set to "1" on exiting
>>> from memory self-refreshing mode. The clobbered interval causes the
>>> "refresh request overflow timeout" error raised by the External Memory
>>> Controller on exiting from LP1 on Tegra30.
>>>
>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>> ---
>>>  arch/arm/mach-tegra/sleep-tegra30.S | 2 --
>>>  1 file changed, 2 deletions(-)
>>>
>>> diff --git a/arch/arm/mach-tegra/sleep-tegra30.S b/arch/arm/mach-tegra/sleep-tegra30.S
>>> index 801fe58978ae..99ac9c6dcf7c 100644
>>> --- a/arch/arm/mach-tegra/sleep-tegra30.S
>>> +++ b/arch/arm/mach-tegra/sleep-tegra30.S
>>> @@ -29,7 +29,6 @@
>>>  #define EMC_CFG				0xc
>>>  #define EMC_ADR_CFG			0x10
>>>  #define EMC_TIMING_CONTROL		0x28
>>> -#define EMC_REFRESH			0x70
>>>  #define EMC_NOP				0xdc
>>>  #define EMC_SELF_REF			0xe0
>>>  #define EMC_MRW				0xe8
>>> @@ -459,7 +458,6 @@ emc_wait_auto_cal_onetime:
>>>  	cmp	r10, #TEGRA30
>>>  	streq	r1, [r0, #EMC_NOP]
>>>  	streq	r1, [r0, #EMC_NOP]
>>> -	streq	r1, [r0, #EMC_REFRESH]
>>>  
>>>  	emc_device_mask r1, r0
>>
>> This does look incorrect and it appears Tegra20 has the same bug.
> 
> Indeed.. somehow this doesn't cause any problems on T20. Maybe this affects only specific timing configurations and it's just a luck that "refresh overflow" isn't getting raised.
> 
>> However, looking at the EMC_REFRESH register it appears that bits 5:0
>> are the REFRESH_LO and bits 15:6 are the refresh interval. So this seems
>> to imply the interval is set to 0 and not 1. So maybe the commit message
>> needs to be fixed up.
> 
> Do you mean that EMC_REFRESH is a fractional value?

No the more I look at this, I just think it is a badly describe register
in the TRM. I think that your description is correct afterall.

Cheers
Jon


-- 
nvpublic