[U-Boot] [PATCH] ARMv7: OMAP: Add init function for TWL4030 GBPR1 register

Igor Grinberg grinberg at compulab.co.il
Sun Mar 4 08:45:28 CET 2012

On 03/01/12 19:47, Jonathan Solnit wrote:
> Hi Igor.
> On Thu, Mar 1, 2012 at 12:41 AM, Igor Grinberg <grinberg at compulab.co.il <mailto:grinberg at compulab.co.il>> wrote:
>     Hi Jonathan,
>     On 02/29/12 22:52, Jonathan Solnit wrote:
>     > The OMAP ROM code modifies the GBPR1 register, which can cause
>     s/GBPR1/GPBR1/
>     > unintended consequences.
>     What do you mean by this?
>     Can you please elaborate, what issues do you see?
>     Also, why does the OMAP ROM code needs to touch the GPBR1?
> For my board, when booting the OMAP3 from MMC1, GPBR1 comes up as 0x00 instead of 0x90.  The improper clock configuration causes timeouts whenever I try to use the MADC.  In Linux, the error looks like this:
> user.err kernel: twl4030_madc twl4030_madc: conversion timeout!

Right, but isn't this has been already fixed in kernel:
3d6271f (mfd: Turn on the twl4030-madc MADC clock)

$ git describe 3d6271f

> As for why ROM touches GPBR1, only TI can answer that.  What I've found is that this is a known issue and re-initializing the register at start-up is the recommended solution:
> http://e2e.ti.com/support/power_management/pmu/f/43/t/762.aspx

We would really appreciate if someone from TI (Tom?) can confirm that this is a bug in ROM code.
Nevertheless, I don't think U-Boot uses MADC feature (am I right?),
so IMO, kernel has to be fixed (I think already fixed) to not rely
on ROM/U-Boot setup of that MADC clock.


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