[U-Boot] [PATCH 1/2] arm: imx6: Add DDR3 calibration code for MX6 Q/D/DL

[Marek Vasut <marex@denx.de>]

On Wednesday, December 16, 2015 at 05:28:48 PM, Eric Nelson wrote:
> Hi Marek,

Hi!

> On 12/16/2015 08:33 AM, Marek Vasut wrote:
> > On Wednesday, December 16, 2015 at 04:00:38 PM, Eric Nelson wrote:
> >> Hi Marek,
> >> 
> >> On 12/16/2015 07:40 AM, Marek Vasut wrote:
> >>> Add DDR3 calibration code for i.MX6Q, i.MX6D and i.MX6DL. This code
> >>> fine-tunes the behavior of the MMDC controller in order to improve
> >>> the signal integrity and memory stability.
> >> 
> >> I'm glad to see that others are interested in this.
> >> 
> >> I've been working on something similar, but struggling to have time
> >> 
> >> to finish and clean it up:
> >> 	https://github.com/ericnelsonaz/u-boot/tree/memcal-pass1
> >> 
> >> My aim is/was a bit different though, and aims to be a replacement for
> >> the DDR stress tool, which is cumbersome to use.
> > 
> > Excellent, we can add this as an optional feature or something which can
> > be triggered by command, since the "full" calibration takes some time.
> > 
> >> To do that, I put together a pseudo-board with Kconfig options for
> >> the serial console, memory bus width, and such.
> > 
> > Or maybe this can be built as a mutated SPL ?
> 
> That's how I have things hacked together. The board "mx6memcal"
> essentially **only** produces SPL.
> 
> It runs calibration, then spits out the results in a form usable by
> either a .cfg file or SPL data structure.
> 
> I'd like to add a trailing memory test with frequency walking as
> done with the DDR stress tool before submitting it though.

Gotcha! That'd be great thing to have %^)

> >>> Signed-off-by: Marek Vasut <marex@denx.de>
> >>> Cc: Stefano Babic <sbabic@denx.de>
> >>> ---
> >>> 
> >>>  arch/arm/cpu/armv7/mx6/ddr.c            | 559
> >>>  ++++++++++++++++++++++++++++++++
> >>>  arch/arm/include/asm/arch-mx6/mx6-ddr.h |   5 +
> >>>  2 files changed, 564 insertions(+)
> >>> 
> >>> diff --git a/arch/arm/cpu/armv7/mx6/ddr.c
> >>> b/arch/arm/cpu/armv7/mx6/ddr.c index 6b039e4..194411f 100644
> >>> --- a/arch/arm/cpu/armv7/mx6/ddr.c
> >>> +++ b/arch/arm/cpu/armv7/mx6/ddr.c
> >>> @@ -13,6 +13,565 @@
> >>> 
> >>>  #include <asm/io.h>
> >>>  #include <asm/types.h>
> >> 
> >> I'll review this in detail later, but off-hand, I think this could use
> >> a new CONFIG_ variable to exclude it from boards that don't use it.
> >> 
> >> It also shouldn't be difficult to support i.MX6SL and LPDDR here.
> > 
> > This is OK, the code will be compiled for these MX6 variants, but it will
> > be dropped from the final binary if you don't call it explicitly (see
> > patch 2/2).
> 
> Gotcha.
> 
> > I don't have SX/SL, so I couldn't test it there.
> 
> I have a couple of SL boards, so I can do that (mx6slevk and a custom
> board using DDR3). Both of them support SPL, so it shouldn't take
> long to validate.

Excellent! Let's do this as a subsequent patch though, since this code is
actually tested extensively and I'd like to keep it as a reference for
possible bisecting ;-)