linux-kernel - [PATCH 1/2] PCI: endpoint: strictly apply bar fixed size to allocate space

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Message-Id: <20250328-pci-ep-size-alignment-v1-1-ee5b78b15a9a@baylibre.com>
Date: Fri, 28 Mar 2025 15:53:42 +0100
From: Jerome Brunet <jbrunet@...libre.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
 Krzysztof Wilczyński <kw@...ux.com>, 
 Kishon Vijay Abraham I <kishon@...nel.org>, 
 Bjorn Helgaas <bhelgaas@...gle.com>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, Jon Mason <jdmason@...zu.us>, 
 Dave Jiang <dave.jiang@...el.com>, Allen Hubbe <allenbh@...il.com>
Cc: Marek Vasut <marek.vasut+renesas@...il.com>, 
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>, 
 Yuya Hamamachi <yuya.hamamachi.sx@...esas.com>, linux-pci@...r.kernel.org, 
 linux-kernel@...r.kernel.org, ntb@...ts.linux.dev, 
 Jerome Brunet <jbrunet@...libre.com>
Subject: [PATCH 1/2] PCI: endpoint: strictly apply bar fixed size to
 allocate space

When trying to allocate space for an endpoint function on a BAR with a
fixed size, that size should be used regardless of the alignment.

Some controller may have specified an alignment, but do have a BAR with a
fixed size smaller that alignment. In such case, pci_epf_alloc_space()
tries to allocate a space that matches the alignment and it won't work.

When the BAR size is fixed, pci_epf_alloc_space() should not deviate
from this fixed size.

Fixes: 2a9a801620ef ("PCI: endpoint: Add support to specify alignment for buffers allocated to BARs")
Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
---
 drivers/pci/endpoint/pci-epf-core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
index 394395c7f8decfa2010469655a4bd58a002993fd..cb985b172ed041c6f319c083f412e51e25b0a157 100644
--- a/drivers/pci/endpoint/pci-epf-core.c
+++ b/drivers/pci/endpoint/pci-epf-core.c
@@ -285,12 +285,11 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
 			return NULL;
 		}
 		size = bar_fixed_size;
-	}
-
-	if (align)
+	} else if (align) {
 		size = ALIGN(size, align);
-	else
+	} else {
 		size = roundup_pow_of_two(size);
+	}
 
 	if (type == PRIMARY_INTERFACE) {
 		epc = epf->epc;

-- 
2.47.2