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

From: [email-masked] (Jon Hunter)
Date: Wed, 25 Apr 2012 10:16:06 -0500

Hi Tero,

On 04/25/2012 02:26 AM, Tero Kristo wrote:
> 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 <[email-masked]>
>>>
>>> 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 <[email-masked]>
>>> [t-kristo at ti.com: moved workaround from omap-sar.c to pm44xx.c]
>>> Signed-off-by: Tero Kristo <[email-masked]>
>>> ---
>>>  .../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.

By the way, I did dump the EMIF1_SDRAM_CONFIG2 register on a omap4403
and it is configured to 0x10. So I think that reading this register and
saving would be safe.

Cheers
Jon