linux-kernel - [RFC PATCH v4 24/38] NTB: ntb_transport: Run ntb_set

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Message-ID: <20260118135440.1958279-25-den@valinux.co.jp>
Date: Sun, 18 Jan 2026 22:54:26 +0900
From: Koichiro Den <den@...inux.co.jp>
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Subject: [RFC PATCH v4 24/38] NTB: ntb_transport: Run ntb_set_mw() before link-up negotiation

Some backends may need to program BAR subrange mappings, and due to
pci_epc_set_bar() submap API constraint, the entire BAR layout needs to
be provided when calling the function. Since one MW that is to be
programmed by ntb_set_mw() can be the last piece that allows us to call
pci_epc_set_bar() for the BAR, calling it only after link-up can race
with post-link-up setup on the host.

Invoke ntb_set_mw() before the link-up handshake so the MW translation
is established early and the post-link-up setup can run without relying
on late MW programming. Since ntb_set_mw() can re-setup the MW when it
turns out that the size differs, it's safe to do so.

Signed-off-by: Koichiro Den <den@...inux.co.jp>
---
 drivers/ntb/ntb_transport_core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/ntb/ntb_transport_core.c b/drivers/ntb/ntb_transport_core.c
index 2129fa7a22d8..185d73f8ea93 100644
--- a/drivers/ntb/ntb_transport_core.c
+++ b/drivers/ntb/ntb_transport_core.c
@@ -977,6 +977,10 @@ static void ntb_transport_link_work(struct work_struct *work)
 
 		spad = MW0_SZ_LOW + (i * 2);
 		ntb_peer_spad_write(ndev, PIDX, spad, lower_32_bits(size));
+
+		rc = ntb_set_mw(nt, i, size);
+		if (rc)
+			goto out;
 	}
 
 	ntb_peer_spad_write(ndev, PIDX, NUM_MWS, nt->mw_count);
@@ -1032,6 +1036,7 @@ static void ntb_transport_link_work(struct work_struct *work)
 
 		dev_dbg(&pdev->dev, "Remote MW%d size = %#llx\n", i, val64);
 
+		/* If it turns out that the size differs, reconfigure it */
 		rc = ntb_set_mw(nt, i, val64);
 		if (rc)
 			goto out1;
-- 
2.51.0