linux-kernel - [PATCH] PCI: apple: Add depends on PAGE_SIZE

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Message-Id: <20250211-pci-16k-v1-1-7fc7b34327f2@rosenzweig.io>
Date: Tue, 11 Feb 2025 13:03:52 -0500
From: Alyssa Rosenzweig <alyssa@...enzweig.io>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Krzysztof Wilczyński <kw@...ux.com>, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Janne Grunau <j@...nau.net>, Alyssa Rosenzweig <alyssa@...enzweig.io>
Subject: [PATCH] PCI: apple: Add depends on PAGE_SIZE_16KB

From: Janne Grunau <j@...nau.net>

The iommu on Apple's M1 and M2 supports only a page size of 16kB and is
mandatory for PCIe devices. Mismatched page sizes will render devices
useless due to non-working DMA. While the iommu prints a warning in this
scenario, it seems a common and hard to debug problem, so prevent it at
build-time.

Signed-off-by: Janne Grunau <j@...nau.net>
Signed-off-by: Alyssa Rosenzweig <alyssa@...enzweig.io>
---
 drivers/pci/controller/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/controller/Kconfig b/drivers/pci/controller/Kconfig
index 9800b768105402d6dd1ba4b134c2ec23da6e4201..507e6ac5d65257578e4eec74b459f6605c9c2907 100644
--- a/drivers/pci/controller/Kconfig
+++ b/drivers/pci/controller/Kconfig
@@ -39,6 +39,7 @@ config PCIE_APPLE
 	depends on ARCH_APPLE || COMPILE_TEST
 	depends on OF
 	depends on PCI_MSI
+	depends on PAGE_SIZE_16KB || COMPILE_TEST
 	select PCI_HOST_COMMON
 	help
 	  Say Y here if you want to enable PCIe controller support on Apple

---
base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b
change-id: 20250211-pci-16k-4c391a5dcd18

Best regards,
-- 
Alyssa Rosenzweig <alyssa@...enzweig.io>