Re: [PATCH 15/19] ARM: OMAP4430: PM: workaround for DDR corruption on second CS

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On Tue, 2012-04-24 at 13:22 -0500, Jon Hunter wrote:
> Hi Tero,
> 
> On 04/20/2012 04:33 AM, Tero Kristo wrote:
> > From: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
> > 
> > Work around for Errata ID: i632 "LPDDR2 Corruption After OFF Mode
> > Transition When CS1 Is Used On EMIF" which impacts OMAP443x silicon
> > The issue occurs when EMIF_SDRAM_CONFIG is restored first before
> > EMIF_SDRAM_CONFIG_2 is not yet restored, the register configuration
> > is not set properly, we apply the required workaround allowing
> > the restore sequence to work properly.
> > 
> > Signed-off-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
> > [t-kristo@xxxxxx: moved workaround from omap-sar.c to pm44xx.c]
> > Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
> > ---
> >  .../include/mach/ctrl_module_wkup_44xx.h           |    2 +
> >  arch/arm/mach-omap2/pm44xx.c                       |   24 ++++++++++++++++++++
> >  2 files changed, 26 insertions(+), 0 deletions(-)
> > 
> > diff --git a/arch/arm/mach-omap2/include/mach/ctrl_module_wkup_44xx.h b/arch/arm/mach-omap2/include/mach/ctrl_module_wkup_44xx.h
> > index a0af9ba..b763a79 100644
> > --- a/arch/arm/mach-omap2/include/mach/ctrl_module_wkup_44xx.h
> > +++ b/arch/arm/mach-omap2/include/mach/ctrl_module_wkup_44xx.h
> > @@ -28,6 +28,8 @@
> >  #define OMAP4_CTRL_MODULE_WKUP_IP_REVISION		0x0000
> >  #define OMAP4_CTRL_MODULE_WKUP_IP_HWINFO		0x0004
> >  #define OMAP4_CTRL_MODULE_WKUP_IP_SYSCONFIG		0x0010
> > +#define OMAP4_CTRL_SECURE_EMIF1_SDRAM_CONFIG2_REG	0x0114
> > +#define OMAP4_CTRL_SECURE_EMIF2_SDRAM_CONFIG2_REG	0x011c
> >  #define OMAP4_CTRL_MODULE_WKUP_CONF_DEBUG_SEL_TST_0	0x0460
> >  #define OMAP4_CTRL_MODULE_WKUP_CONF_DEBUG_SEL_TST_1	0x0464
> >  #define OMAP4_CTRL_MODULE_WKUP_CONF_DEBUG_SEL_TST_2	0x0468
> > diff --git a/arch/arm/mach-omap2/pm44xx.c b/arch/arm/mach-omap2/pm44xx.c
> > index 0472921..d4d18d9 100644
> > --- a/arch/arm/mach-omap2/pm44xx.c
> > +++ b/arch/arm/mach-omap2/pm44xx.c
> > @@ -17,6 +17,9 @@
> >  #include <linux/err.h>
> >  #include <linux/slab.h>
> >  #include <asm/system_misc.h>
> > +#include <linux/io.h>
> > +
> > +#include <mach/ctrl_module_wkup_44xx.h>
> >  
> >  #include "common.h"
> >  #include "clockdomain.h"
> > @@ -215,6 +218,27 @@ static int __init omap4_pm_init(void)
> >  
> >  	pr_err("Power Management for TI OMAP4.\n");
> >  
> > +	/*
> > +	 * Work around for OMAP443x Errata i632: "LPDDR2 Corruption After OFF
> > +	 * Mode Transition When CS1 Is Used On EMIF":
> > +	 * Overwrite EMIF1/EMIF2
> > +	 * SECURE_EMIF1_SDRAM_CONFIG2_REG
> > +	 * SECURE_EMIF2_SDRAM_CONFIG2_REG
> > +	 */
> > +	if (cpu_is_omap443x()) {
> > +		void __iomem *secure_ctrl_mod;
> > +
> > +		secure_ctrl_mod = ioremap(OMAP4_CTRL_MODULE_WKUP, SZ_4K);
> > +		BUG_ON(!secure_ctrl_mod);
> > +
> > +		__raw_writel(0x10, secure_ctrl_mod +
> > +			     OMAP4_CTRL_SECURE_EMIF1_SDRAM_CONFIG2_REG);
> > +		__raw_writel(0x10, secure_ctrl_mod +
> > +			     OMAP4_CTRL_SECURE_EMIF2_SDRAM_CONFIG2_REG);
> 
> According to the erratum description the above registers are used to
> restore the EMIFx_SDRAM_CONFIG2 registers. So although the value 0x10,
> maybe the value being used for EMIFx_SDRAM_CONFIG2 registers, shouldn't
> we read the EMIFx_SDRAM_CONFIG2 registers and store them in the above
> registers?

This might be a good idea, however, this patch might be tagged as TEMP
until the EMIF driver is in place, this fix should rather be located
there. I'll take a look at this if I can change the implementation a
bit.

-Tero

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