Dear Wolfgang Denk,
-----Original Message----- From: Wolfgang Denk [mailto:wd@denx.de] Sent: Sunday, September 26, 2010 8:07 PM To: Nishanth Menon Cc: V, Aneesh; u-boot@lists.denx.de; Steve Sakoman Subject: Re: [U-Boot] [PATCH] ARMV7: OMAP4: Calculate SDRAM size
Dear Nishanth Menon,
In message 4C9F3E4F.3040403@gmail.com you wrote:
I think you are referring to SDRAM initialization. Yes, it is
assumed
that SDRAM initialization(at least the DMM part of it) is done
before
the call to sdram_size(). The right location for this seems to be the initial part of sdram_init().
thanks for the clarification.. NOR boot is usually going to have
initial
part in XIP -> we'd traditionally relocate to SDRAM before the
call to
sdram_size() happens.
Yes, this was the way how many ARM boards id, and this is what I'm trying to explain: this is WRONG.
SDRAM configuration must be done while still running from NOR, i. e. before relocation. Only then free reconfiguration, auto-sizing etc. is possible.
We shall rework the patch to do SDRAM size calculation as part of 'lowlevel_init' that is called before relocation. I hope that should solve the problem.
Please note that we are always running from SDRAM because none of the OMAP4 boards so far have any XIP device.
Regarding true run-time detection of SDRAM size and configuration: We do not support it today. However, LPDDR2 supports Mode Registers that have size info and our memory controller can read it. This coupled with the base AC timings specified by the LPDDR2 spec creates the possibility of doing a truly run-time detection and configuration of SDRAM that works for all boards. I was indeed thinking of trying it out sometime. Please note that the base AC timing values may not be optimal for all memory parts.
Best regards, Aneesh