linux-kernel - [PATCH v2 3/3] PCI: endpoint: pci-epf-vntb: simplify ctrl/spad space allocation

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Message-Id: <20250404-pci-ep-size-alignment-v2-3-c3a0db4cfc57@baylibre.com>
Date: Fri, 04 Apr 2025 19:46:22 +0200
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 v2 3/3] PCI: endpoint: pci-epf-vntb: simplify ctrl/spad
 space allocation

When allocating the shared ctrl/spad space, epf_ntb_config_spad_bar_alloc()
should not try to handle the size quirks for underlying BAR, whether it is
fixed size or alignment. This is already handled by pci_epf_alloc_space().

Also, when handling the alignment, this allocate more space than necessary.
For example, with a spad size of 1024B and a ctrl size of 308B, the space
necessary is 1332B. If the alignment is 1MB,
epf_ntb_config_spad_bar_alloc() tries to allocate 2MB where 1MB would have
been more than enough.

Drop the handling of the BAR size quirks and let
pci_epf_alloc_space() handle that. Just make sure the 32bits SPAD register
are aligned on 32bits.

Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
---
 drivers/pci/endpoint/functions/pci-epf-vntb.c | 26 +++-----------------------
 1 file changed, 3 insertions(+), 23 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
index 8f59a5b9b7adec2c05eebae71c6a246bc5a8e88c..bc4a9c7c4338db6cc89fa47de89dc704d0a03806 100644
--- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
+++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
@@ -413,11 +413,9 @@ static void epf_ntb_config_spad_bar_free(struct epf_ntb *ntb)
  */
 static int epf_ntb_config_spad_bar_alloc(struct epf_ntb *ntb)
 {
-	size_t align;
 	enum pci_barno barno;
 	struct epf_ntb_ctrl *ctrl;
 	u32 spad_size, ctrl_size;
-	u64 size;
 	struct pci_epf *epf = ntb->epf;
 	struct device *dev = &epf->dev;
 	u32 spad_count;
@@ -427,31 +425,13 @@ static int epf_ntb_config_spad_bar_alloc(struct epf_ntb *ntb)
 								epf->func_no,
 								epf->vfunc_no);
 	barno = ntb->epf_ntb_bar[BAR_CONFIG];
-	size = epc_features->bar[barno].fixed_size;
-	align = epc_features->align;
-
-	if ((!IS_ALIGNED(size, align)))
-		return -EINVAL;
-
 	spad_count = ntb->spad_count;
 
-	ctrl_size = sizeof(struct epf_ntb_ctrl);
+	ctrl_size = ALIGN(sizeof(struct epf_ntb_ctrl), sizeof(u32));
 	spad_size = 2 * spad_count * sizeof(u32);
 
-	if (!align) {
-		ctrl_size = roundup_pow_of_two(ctrl_size);
-		spad_size = roundup_pow_of_two(spad_size);
-	} else {
-		ctrl_size = ALIGN(ctrl_size, align);
-		spad_size = ALIGN(spad_size, align);
-	}
-
-	if (!size)
-		size = ctrl_size + spad_size;
-	else if (size < ctrl_size + spad_size)
-		return -EINVAL;
-
-	base = pci_epf_alloc_space(epf, size, barno, epc_features, 0);
+	base = pci_epf_alloc_space(epf, ctrl_size + spad_size,
+				   barno, epc_features, 0);
 	if (!base) {
 		dev_err(dev, "Config/Status/SPAD alloc region fail\n");
 		return -ENOMEM;

-- 
2.47.2