linux-kernel - [PATCH v2 3/6] iommu/exynos: Modularize the driver

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Date:   Thu,  3 Nov 2022 20:51:51 +0100
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Janghyuck Kim <janghyuck.kim@...sung.com>,
        Cho KyongHo <pullip.cho@...sung.com>,
        Daniel Mentz <danielmentz@...gle.com>,
        David Virag <virag.david003@...il.com>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org
Subject: [PATCH v2 3/6] iommu/exynos: Modularize the driver

Rework the driver so it can be built as a loadable module. That can be
useful as not all ARM64 platforms need it. And that's ok for it to be a
module because it's not a critical driver (platform can work when it's
disabled).

Remove method and module exit function are not implemented, as the
removal of IOMMUs cannot be done reliably. As Robin Murphy mentioned in
[1]:

    ...it's better not to even pretend that removing an IOMMU's driver
    while other drivers are using it (usually via DMA ops without even
    realising) is going to have anything other than catastrophic
    results.

[1] https://lore.kernel.org/lkml/20220702213724.3949-2-semen.protsenko@linaro.org/T/#md7e1e3f5b2c9e7fa5bc28fe33e818b6aa4a7237c

Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
---
Changes in v2:
  - Add MODULE_DEVICE_TABLE(of, ...) to support hot-plug loading
  - Add MODULE_ALIAS() line
  - Extracted "shutdown" driver method adding into a separate patch

 drivers/iommu/Kconfig        | 2 +-
 drivers/iommu/exynos-iommu.c | 9 ++++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index dc5f7a156ff5..6f7055606679 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -259,7 +259,7 @@ config TEGRA_IOMMU_SMMU
 	  SoCs (Tegra30 up to Tegra210).
 
 config EXYNOS_IOMMU
-	bool "Exynos IOMMU Support"
+	tristate "Exynos IOMMU Support"
 	depends on ARCH_EXYNOS || COMPILE_TEST
 	depends on !CPU_BIG_ENDIAN # revisit driver if we can enable big-endian ptes
 	select IOMMU_API
diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
index 0d150b383d04..aad845677bda 100644
--- a/drivers/iommu/exynos-iommu.c
+++ b/drivers/iommu/exynos-iommu.c
@@ -16,6 +16,7 @@
 #include <linux/interrupt.h>
 #include <linux/kmemleak.h>
 #include <linux/list.h>
+#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
@@ -798,8 +799,9 @@ static const struct of_device_id sysmmu_of_match[] = {
 	{ .compatible	= "samsung,exynos-sysmmu", },
 	{ },
 };
+MODULE_DEVICE_TABLE(of, sysmmu_of_match);
 
-static struct platform_driver exynos_sysmmu_driver __refdata = {
+static struct platform_driver exynos_sysmmu_driver = {
 	.probe	= exynos_sysmmu_probe,
 	.driver	= {
 		.name		= "exynos-sysmmu",
@@ -1404,6 +1406,7 @@ static const struct iommu_ops exynos_iommu_ops = {
 	.release_device = exynos_iommu_release_device,
 	.pgsize_bitmap = SECT_SIZE | LPAGE_SIZE | SPAGE_SIZE,
 	.of_xlate = exynos_iommu_of_xlate,
+	.owner = THIS_MODULE,
 	.default_domain_ops = &(const struct iommu_domain_ops) {
 		.attach_dev	= exynos_iommu_attach_device,
 		.detach_dev	= exynos_iommu_detach_device,
@@ -1454,3 +1457,7 @@ static int __init exynos_iommu_init(void)
 	return ret;
 }
 core_initcall(exynos_iommu_init);
+
+MODULE_DESCRIPTION("IOMMU driver for Exynos SoCs");
+MODULE_ALIAS("platform:exynos-sysmmu");
+MODULE_LICENSE("GPL");
-- 
2.35.1