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

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Date:   Tue, 20 Nov 2018 10:26:14 +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 22:32, Dmitry Osipenko wrote:
> On 20.11.2018 1:09, 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.
> 
> Ah, T20 exit_selfrefresh_loop doesn't latch registers.. that's probably why it stayed unnoticed.

Good to know.

Cheers Jon

-- 
nvpublic