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Commit 5f1b1f06 authored by Logan Gunthorpe's avatar Logan Gunthorpe Committed by Jon Mason
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NTB: Introduce functions to calculate multi-port resource index 



When using multi-ports each port uses resources (dbs, msgs, mws, etc)
on every other port. Creating a mapping for these resources such that
each port has a corresponding resource on every other port is a bit
tricky.

Introduce the ntb_peer_resource_idx() function for this purpose.
It returns the peer resource number that will correspond with the
local peer index on the remote peer.

Also, introduce ntb_peer_highest_mw_idx() which will use
ntb_peer_resource_idx() but return the MW index starting with the
highest index and working down.

Signed-off-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Allen Hubbe <allenbh@gmail.com>
Signed-off-by: default avatarJon Mason <jdmason@kudzu.us>
parent 246a42c5

include/linux/ntb.h

+70 −0
Original line number Diff line number Diff line
@@ -1557,4 +1557,74 @@ static inline int ntb_peer_msg_write(struct ntb_dev *ntb, int pidx, int midx, 
	return ntb->ops->peer_msg_write(ntb, pidx, midx, msg);

}



/**

 * ntb_peer_resource_idx() - get a resource index for a given peer idx

 * @ntb:	NTB device context.

 * @pidx:	Peer port index.

 *

 * When constructing a graph of peers, each remote peer must use a different

 * resource index (mw, doorbell, etc) to communicate with each other

 * peer.

 *

 * In a two peer system, this function should always return 0 such that

 * resource 0 points to the remote peer on both ports.

 *

 * In a 5 peer system, this function will return the following matrix

 *

 * pidx \ port    0    1    2    3    4

 * 0              0    0    1    2    3

 * 1              0    1    1    2    3

 * 2              0    1    2    2    3

 * 3              0    1    2    3    3

 *

 * For example, if this function is used to program peer's memory

 * windows, port 0 will program MW 0 on all it's peers to point to itself.

 * port 1 will program MW 0 in port 0 to point to itself and MW 1 on all

 * other ports. etc.

 *

 * For the legacy two host case, ntb_port_number() and ntb_peer_port_number()

 * both return zero and therefore this function will always return zero.

 * So MW 0 on each host would be programmed to point to the other host.

 *

 * Return: the resource index to use for that peer.

 */

static inline int ntb_peer_resource_idx(struct ntb_dev *ntb, int pidx)

{

	int local_port, peer_port;



	if (pidx >= ntb_peer_port_count(ntb))

		return -EINVAL;



	local_port = ntb_logical_port_number(ntb);

	peer_port = ntb_peer_logical_port_number(ntb, pidx);



	if (peer_port < local_port)

		return local_port - 1;

	else

		return local_port;

}



/**

 * ntb_peer_highest_mw_idx() - get a memory window index for a given peer idx

 *	using the highest index memory windows first

 *

 * @ntb:	NTB device context.

 * @pidx:	Peer port index.

 *

 * Like ntb_peer_resource_idx(), except it returns indexes starting with

 * last memory window index.

 *

 * Return: the resource index to use for that peer.

 */

static inline int ntb_peer_highest_mw_idx(struct ntb_dev *ntb, int pidx)

{

	int ret;



	ret = ntb_peer_resource_idx(ntb, pidx);

	if (ret < 0)

		return ret;



	return ntb_mw_count(ntb, pidx) - ret - 1;

}



#endif