Hi York, I was thinking about your problem and this could be a solution mpc85xx uses a family of ddr controllers. I believe they would be migrated to LayerScape,
Freescale has also i.mx4/5/6 series and coming i.mx8, that series uses/might use another ddr controller Option1 As you suggested which looks a worthy option. ddr/fsl/contoller1/ --- for 85xx ddr/fsl/contoller2/ --- for I.mx in your board config file, you might want to use CONFIG_DDR_CONTROLLER_MPC85xx or CONFIG_DDR_CONTROLLER_IMX PS: I see no direct relation between ddr controller and core, also freescale is going core agnostic so I think the ddr controller be moved from cpu folder to driver/ddr folder. -Regards mj On Fri, Sep 20, 2013 at 3:19 AM, York Sun <york...@freescale.com> wrote: > On 09/19/2013 02:33 PM, Tom Rini wrote: > > On 09/19/2013 05:08 PM, York Sun wrote: > >> On 09/19/2013 01:57 PM, Tom Rini wrote: > >>> On Tue, Sep 17, 2013 at 08:59:24AM -0700, York Sun wrote: > >>> > >>>> Albert, > >>>> > >>>> Pardon me if this is a dumb question. I have been working on > >>>> powerpc platforms in the past. Now we (the developers I work > >>>> with) are exploring ARM cores. I am searching how memory is > >>>> initialized and found different solutions. Some platforms have > >>>> memory ready before u-boot even starts, some simply write to a > >>>> set of registers. I understand many platforms don't share the > >>>> IP of DDR controller. I am wondering if there is generic DDR > >>>> driver used by many ARM platforms, like the one we have for > >>>> powerpc/mpc85xx SoCs. > >>> > >>> Thinking back, as a rule of thumb, PowerPC has SPD I2C data > >>> available, usually. That's not the rule for ARM. One of a few > >>> choices happen: 1) ROM sets up DDR. 2) U-Boot/SPL sets up the DDR > >>> controller. > >>> > > > >> So for ARM platforms, the majority don't have the flexibility of > >> using different DIMMs and/or clocks? > > > > It's a different world. Again, thinking back to the PowerPC boards > > I've seen, they had "regular" DDR sockets. Most ARM boards don't. > > You can design your board with whatever, and I know in prototyping > > folks make do swapping chips in and out (and if you look at the omap > > code, you can see where we have code to calculate the timing values > > and print them, or use provided hard-coded values). > > Understood. We may have boards with DIMM slots. I do see value of a > fully functional DDR driver here. > > > > >>> The problem is that the DDR controller is usually > >>> vendor-specific. Perhaps the flip-side here is that there's not > >>> so much a generic DDR driver for mpc85xx but simply one vendor > >>> for mpc85xx. Taking arch/powerpc/cpu/mpc85xx/ddr-gen3.c as what > >>> you're talking about, > >>> arch/arm/cpu/armv7/omap-common/emif-common.c would be an > >>> ARM-world example (the 'EMIF' is found on a large variety of TI > >>> parts, not just "omap" ones). > > > >> Does it make sense to share the Freescale DDR driver across ARM > >> and Powerpc? Or does it make more sense to selectively copy the > >> mpc8xxx DDR driver to Freescale ARM subfolder to start with. If the > >> similarity sustains then we merge them into common driver. If not, > >> we maintain two separated drivers. > > > >> For those who is not familiar with, Freescale is extending products > >> to ARM cores. I am expecting peripherals stay relatively close, so > >> many driver can be reused. > > > > I've been wondering when this would start to be visible. If we are > > able to share the DDR controller code between mpc85xx and the ARM > > stuff you're talking about, we'll have to sort out someplace within > > drivers/ to place it, to avoid #include nightmares I suspect. Other > > drivers should be easier to share at least :) > > > > I did a quick and dirty hack yesterday to move DDR driver to > drivers/ddr/fsl. I had to change many #include <asm/????>. > > York > > > > _______________________________________________ > U-Boot mailing list > U-Boot@lists.denx.de > http://lists.denx.de/mailman/listinfo/u-boot > -- -mj
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