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

[Joakim Tjernlund]

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