[U-Boot] [PATCH] driver/ddr/fsl: Force enabling parity for A-009803

[York Sun <york.sun@nxp.com>]

On 05/23/2016 10:15 PM, Shengzhou Liu wrote:
> 
>> -----Original Message-----
>> From: York Sun [mailto:york.sun at nxp.com]
>> Sent: Monday, May 23, 2016 11:33 PM
>> To: Shengzhou Liu <shengzhou.liu@nxp.com>; u-boot at lists.denx.de
>> Subject: Re: [PATCH] driver/ddr/fsl: Force enabling parity for A-009803
>> Shengzhou,
>>
>> My point is you should force ap=1. Do you mean if ERRATUM_A009803 is
>> enabled, users are forced to use address parity? That doesn't sound right.
>> We have been running UDIMM without address parity for a long time.
>>
>> York
>>
> York,
> My understanding is that ERRATUM_A009803 may still happen whatever ap_en is enabled or disabled. 
> To apply the workaround of A009803, it requires ap_en is enabled. Is your understanding that if we
> disable ap_en, ERRATUM_A009803 will never happen?  The CE document doesn't explain clearly this.
> In last mail, did you mean we should force ap_en = 0 in case of A-009803?
> 

Sorry I had a typo. I meant you should NOT force ap=1. Let me explain.
The erratum tells you _if_ address parity is used, for either UDIMM or RDIMM,
you need to implement the workaround, as step 1, 2, 3, ... We understand users
don't have a choice for RDIMM, the address parity is always enabled. But for
UDIMM, users can choose not to enable it. Your _this_ patch forces the address
parity to be true, regardless of user's choice. I think this is wrong.

The erratum always applies to affected SoCs, but the address parity is not
always enabled. That's what I meant for "condition".

York