[U-Boot] [PATCH v1 0/7] Enable high speed and heavy load for DDR4 for LSCH3

[York Sun <yorksun@freescale.com>]

On 11/05/2015 11:53 AM, Joakim Tjernlund wrote:
> On Thu, 2015-11-05 at 10:29 -0800, York Sun wrote:
>>
>> On 11/05/2015 10:19 AM, Joakim Tjernlund wrote:
>>> On Thu, 2015-11-05 at 09:42 -0800, York Sun wrote:
>>>>
>>>> On 11/05/2015 01:55 AM, Joakim Tjernlund wrote:
>>>>> On Thu, 2015-11-05 at 08:23 +0000, Yuantian Tang wrote:
>>>>>> Hi Jocke,
>>>>>>
>>>>>> we achieved deep sleep mode that did exactly what you asked for.
>>>>>> If waken up from deep sleep, soc will resume from uboot and re-initialized DDR controller with
>>>>>> contents
>>>>>> untouched.
>>>>>> Please refer to drivers/ddr/fsl/fsl_ddr_gen4.c and look at DEEP_SLEEP related code.
>>>>>
>>>>> Looking at it now and it looks the same as for ddr3? Some questions though:
>>>>>  289		if (is_warm_boot()) {
>>>>>  289                 /* enter self-refresh */
>>>>>  290                 temp_sdram_cfg = ddr_in32(&ddr->sdram_cfg_2);
>>>>>  291                 temp_sdram_cfg |= SDRAM_CFG2_FRC_SR;
>>>>>  292                 ddr_out32(&ddr->sdram_cfg_2, temp_sdram_cfg);
>>>>>
>>>>> Why do you need to force SR here? The DDR RAM must already be in SR at this point?
>>>>> I come from CPU reset state so my DDR controller has HW default values so
>>>>> this does not feel safe.
>>>>
>>>> This may be redundant. If the code runs to this line, it should come back from a
>>>> deep sleep. The core is in reset state but the DDR controller is not. It should
>>>> be in self-refresh mode. I will leave that to Yuantian to comment.
>>>
>>> OK
>>>
>>>>
>>>>>
>>>>>  293                 /* do board specific memory setup */
>>>>>  294                 board_mem_sleep_setup();
>>>>>  295 
>>>>>  296                 temp_sdram_cfg = (ddr_in32(&ddr->sdram_cfg) | SDRAM_CFG_BI);
>>>>> SDRAM_CFG_BI skips a lot(all?) init of DDR RAM. What if you want to change some DDR RAM
>>>>> timing/config due to a bug? Then you would have to force a cold start.
>>>>>
>>>>> Do you use ECC? Seems to be some issues with ECC if you skip D_INIT
>>>>>
>>>>
>>>> To perform a warm start, the data in DDR is preserved. So you don't need to init
>>>> the data again for ECC. To preserve data, you cannot run D_INIT again, which
>>>> will destroy the data for sure.
>>>
>>> yes, but what about SDRAM_CFG_BI? Why do you need to set that here?
>>> I much rather just skip D_INIT and reconfigure DDR RAM, just in case one wants
>>> to correct some aspect of DDR config in later releases and feels a lot more robust.
>>>
>>> Our systems cannot be coldstarted just because you upgrade SW on them.
>>
>> Jocke,
>>
>> If your memory has been intialized, you can set [BI] bit to bypass
>> re-initialization. It does different things than D_INIT. In short, D_INIT
>> initialize the data, i.e. the content of DDR, while BI bypassing initializing
>> DDR memory (or "chip" if that is easier to understand).
> 
> Yes, that is what I want, reinit of chip, but not data contents.
> I wrote why:
> "just in case one wants to correct some aspect of DDR config in later releases and feels a lot more robust"

Jocke,

I am not 100% sure. I will take this question to our DDR designer.

York