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

[York Sun]

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.

> 
>  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.

York