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Subject: Re: [PATCH] cxl: Add support for ASB_Notify on POWER9
To: benh@au1.ibm.com, linuxppc-dev@lists.ozlabs.org,
 fbarrat@linux.vnet.ibm.com, vaibhav@linux.vnet.ibm.com,
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References: <1511435132-24020-1-git-send-email-clombard@linux.vnet.ibm.com>
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From: christophe lombard <clombard@linux.vnet.ibm.com>
Date: Fri, 24 Nov 2017 11:14:08 +0100
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Le 23/11/2017 à 21:41, Benjamin Herrenschmidt a écrit :
> On Thu, 2017-11-23 at 12:05 +0100, Christophe Lombard wrote:
>> The POWER9 core supports a new feature: ASB_Notify which requires the
>> support of the Special Purpose Register: TIDR.
>>
>> The ASB_Notify command, generated by the AFU, will attempt to
>> wake-up the host thread identified by the particular LPID:PID:TID.
>>
>> This patch assign a unique TIDR (thread id) for the current thread which
>> will be used in the process element entry.
> 
> Is that keyd off some device-tree property or similar ? There is no
> guarantee that the TIDR and ASB_Notify still exist on future chips...
> 
> Ben.
> 

To my knowledge, there is no property (or similar), somewhere, that
indicating that the TIDR is supported or not.
For the time being, if I am not wrong, the only check we have, is
this condition in the function set_thread_tidr(struct task_struct *t):

	if (!cpu_has_feature(CPU_FTR_ARCH_300))
		return -EINVAL;


Christophe