Re: [PATCHv2 15/19] ARM: OMAP4430: PM: workaround for DDR corruption on second CS

[Kevin Hilman <khilman@ti.com>]

"Shilimkar, Santosh" <santosh.shilimkar@ti.com> writes:

> On Thu, May 17, 2012 at 5:45 AM, Kevin Hilman <khilman@ti.com> wrote:
>> Tero Kristo <t-kristo@ti.com> writes:
>>
>>> From: Santosh Shilimkar <santosh.shilimkar@ti.com>
>>>
>>> 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.
>>
>> Please summarize the workaround here as well.
>>
> ok
>>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
>>> [t-kristo@ti.com: moved workaround from omap-sar.c to pm44xx.c]
>>> Signed-off-by: Tero Kristo <t-kristo@ti.com>
>>> ---
>>>  .../include/mach/ctrl_module_wkup_44xx.h           |    2 +
>>>  arch/arm/mach-omap2/pm44xx.c                       |   37 ++++++++++++++++++++
>>>  2 files changed, 39 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 215b80e..dfaa254 100644
>>> --- a/arch/arm/mach-omap2/pm44xx.c
>>> +++ b/arch/arm/mach-omap2/pm44xx.c
>>> @@ -17,12 +17,18 @@
>>>  #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 <mach/hardware.h>
>>>
>>>  #include "common.h"
>>>  #include "clockdomain.h"
>>>  #include "powerdomain.h"
>>>  #include "pm.h"
>>>
>>> +#define EMIF_SDRAM_CONFIG2_OFFSET    0xc
>>> +
>>>  struct power_state {
>>>       struct powerdomain *pwrdm;
>>>       u32 next_state;
>>> @@ -215,6 +221,37 @@ 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()) {
>>
>> This should probably be done later in this function, after PM_ERRATUM
>> flags are setup, and then it should use a PM_ERRATUM flag instead of cpu_is*
>>
> ok
>
>>> +             void __iomem *secure_ctrl_mod;
>>> +             void __iomem *emif1;
>>> +             void __iomem *emif2;
>>> +             u32 val;
>>> +
>>> +             secure_ctrl_mod = ioremap(OMAP4_CTRL_MODULE_WKUP, SZ_4K);
>>> +             emif1 = ioremap(OMAP44XX_EMIF1_BASE, SZ_1M);
>>> +             emif2 = ioremap(OMAP44XX_EMIF2_BASE, SZ_1M);
>>> +
>>> +             BUG_ON(!secure_ctrl_mod || !emif1 || !emif2);
>>
>> Please avoid BUG_ON() and use proper error recovery.  This is not a
>> condition where the entire kernel should panic.
>>
> Agree. WARN_ON() should suffice.

A WARN_ON() is ok (but noisy).  Better is a pr_warn() with some proper
error recovery.

Kevin
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