linux-kernel - Re: [PATCH 3/7] RapidIO: Add Port-Write handling for EM

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Date:	Thu, 25 Feb 2010 22:02:42 +0100
From:	Micha Nelissen <micha@...i.hopto.org>
To:	"Bounine, Alexandre" <Alexandre.Bounine@....com>
CC:	mporter@...nel.crashing.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, thomas.moll.ext@....com,
	thomas.moll@...go.com, Alexandre Bounine <alexb@...dra.com>
Subject: Re: [PATCH 3/7] RapidIO: Add Port-Write handling for EM

Bounine, Alexandre wrote:
> Micha Nelissen wrote:
>> Alexandre Bounine wrote:
>>>  /**
>>> + * rio_em_set_ops- Sets Error Managment operations for a particular
> vendor switch
>>> + * @rdev: RIO device
>>> + *
>>> + * Searches the RIO EM ops table for known switch types. If the vid
>>> + * and did match a switch table entry, then set the em_init() and
>>> + * em_handle() ops to the table entry values.
>> Shouldn't any RIO device be able to support error management, not just
>> switches?
> 
> Only if a device reports this capability by having Error Management
> Extended Features block.
> Ideally, we have to provide default handler for every such device (I am
> planning it for some future updates). It should be the same as for
> routing operations - if the standard feature exists, it has to be used
> unless something else takes over.

Yes, therefore I thought that: or the EM_OPS are per driver, or they can 
be integrated in the switch hooks list.

> For now I keep all port-write messages from end-points serviced by their
> individual drivers. One of reasons for this: the EM PW message format

Maybe have a generic rio function that can be called by any driver that 
knows a particular port-write was due to error management causes? This 
function would read the standard defined EF block registers. Then the 
driver part can be quite small.

>>> +	if (port->ops->pwenable)
>>> +		port->ops->pwenable(port, enable);
>>> +}
>>> +
>> Maybe this can be done by switch->init function?
> 
> This is not per-switch function. This function enables mport to receive
> incoming PW messages. Per-switch PW enable is done in switch->init as
> for Tsi57x. 

Oops, I meant this comment for the em_init function call.

>>> +			rio_mport_write_config_32(mport, destid,
> hopcount,
>>> +				rdev->phys_efptr +
>>> +					RIO_PORT_N_ACK_STS_CSR(portnum),
>>> +				RIO_PORT_N_ACK_CLEAR);
>> This doesn't work for the 568; but the 568 has no special handling?
> 
> Tsi568 will not send EM PW message. Tsi568 PWs are disabled in its
> em_init().

Why?

>>> +DECLARE_RIO_EM_OPS(RIO_VID_TUNDRA, RIO_DID_TSI578, tsi57x_em_init,
> tsi57x_em_handler);
>> Why not declare these along with the other ops?
> 
> Because the EM extensions is a separate capability. It is not guaranteed
> to be in every switch.

They might initialize them with NULL to indicate they don't support it?

Micha
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