Message-Id: <1443914889-9619-3-git-send-email-somlo@cmu.edu>
Date:	Sat,  3 Oct 2015 19:28:07 -0400
From:	"Gabriel L. Somlo" <somlo@....edu>
To:	gregkh@...uxfoundation.org, paul@...an.com, galak@...eaurora.org,
	will.deacon@....com, agross@...eaurora.org, mark.rutland@....com,
	zajec5@...il.com, hanjun.guo@...aro.org, catalin.marinas@....com,
	linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	kernelnewbies@...nelnewbies.org, matt.fleming@...el.com,
	lersek@...hat.com, jordan.l.justen@...el.com, mst@...hat.com,
	peter.maydell@...aro.org, leif.lindholm@...aro.org,
	ard.biesheuvel@...aro.org, pbonzini@...hat.com, kraxel@...hat.com,
	qemu-devel@...gnu.org
Subject: [PATCH v3 2/4] firmware: use acpi to detect QEMU fw_cfg device for sysfs fw_cfg driver

From: Gabriel Somlo <somlo@....edu>

Instead of blindly probing fw_cfg registers at known IOport and MMIO
locations, use the ACPI subsystem to determine whether a QEMU fw_cfg
device is present, and, if found, to initialize it.

This limits portability to architectures which support ACPI (x86 and
UEFI-enabled aarch64), but avoids touching hardware registers before
being certain that our device is present.

NOTE: The standard way to verify the presence of fw_cfg on arm VMs
would have been to use the device tree, but that would have left out
x86, which is the primary architecture targeted by this patch.

Signed-off-by: Gabriel Somlo <somlo@....edu>
---
 .../ABI/testing/sysfs-firmware-qemu_fw_cfg         |   4 +
 drivers/firmware/Kconfig                           |   2 +-
 drivers/firmware/qemu_fw_cfg.c                     | 201 +++++++++++----------
 3 files changed, 113 insertions(+), 94 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg b/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
index f1ef44e..e9761bf 100644
--- a/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
+++ b/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
@@ -76,6 +76,10 @@ Description:
 		the port number of the control register. I.e., the two ports
 		are overlapping, and can not be mapped separately.
 
+		NOTE 2. QEMU publishes the register details in the device tree
+		on arm guests, and in ACPI (under _HID "QEMU0002") on x86 and
+		select arm (aarch64) VM types.
+
 		=== Firmware Configuration Items of Interest ===
 
 		Originally, the index key, size, and formatting of blobs in
diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index 0466e80..bc12d31 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -137,7 +137,7 @@ config ISCSI_IBFT
 
 config FW_CFG_SYSFS
 	tristate "QEMU fw_cfg device support in sysfs"
-	depends on SYSFS
+	depends on SYSFS && ACPI
 	default n
 	help
 	  Say Y or M here to enable the exporting of the QEMU firmware
diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index 3a67a16..f935afb 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/module.h>
+#include <linux/acpi.h>
 #include <linux/slab.h>
 #include <linux/io.h>
 #include <linux/ioport.h>
@@ -35,53 +36,10 @@ struct fw_cfg_file {
 	char name[FW_CFG_MAX_FILE_PATH];
 };
 
-/* fw_cfg device i/o access options type */
-struct fw_cfg_access {
-	const char *name;
-	phys_addr_t base;
-	u8 size;
-	u8 ctrl_offset;
-	u8 data_offset;
-	bool is_mmio;
-};
-
-/* table of fw_cfg device i/o access options for known architectures */
-static struct fw_cfg_access fw_cfg_modes[] = {
-	{
-		.name = "fw_cfg IOport on i386, sun4u",
-		.base = 0x510,
-		.size = 0x02,
-		.ctrl_offset = 0x00,
-		.data_offset = 0x01,
-		.is_mmio = false,
-	}, {
-		.name = "fw_cfg MMIO on arm",
-		.base = 0x9020000,
-		.size = 0x0a,
-		.ctrl_offset = 0x08,
-		.data_offset = 0x00,
-		.is_mmio = true,
-	}, {
-		.name = "fw_cfg MMIO on sun4m",
-		.base = 0xd00000510,
-		.size = 0x03,
-		.ctrl_offset = 0x00,
-		.data_offset = 0x02,
-		.is_mmio = true,
-	}, {
-		.name = "fw_cfg MMIO on ppc/mac",
-		.base = 0xf0000510,
-		.size = 0x03,
-		.ctrl_offset = 0x00,
-		.data_offset = 0x02,
-		.is_mmio = true,
-	}, { } /* END */
-};
-
-/* fw_cfg device i/o currently selected option set */
-static struct fw_cfg_access *fw_cfg_mode;
-
 /* fw_cfg device i/o register addresses */
+static bool fw_cfg_is_mmio;
+static phys_addr_t fw_cfg_phys_base;
+static u32 fw_cfg_phys_size;
 static void __iomem *fw_cfg_dev_base;
 static void __iomem *fw_cfg_reg_ctrl;
 static void __iomem *fw_cfg_reg_data;
@@ -92,7 +50,7 @@ static DEFINE_MUTEX(fw_cfg_dev_lock);
 /* pick appropriate endianness for selector key */
 static inline u16 fw_cfg_sel_endianness(u16 key)
 {
-	return fw_cfg_mode->is_mmio ? cpu_to_be16(key) : cpu_to_le16(key);
+	return fw_cfg_is_mmio ? cpu_to_be16(key) : cpu_to_le16(key);
 }
 
 /* type for fw_cfg "directory scan" visitor/callback function */
@@ -133,60 +91,100 @@ static inline void fw_cfg_read_blob(u16 key,
 /* clean up fw_cfg device i/o */
 static void fw_cfg_io_cleanup(void)
 {
-	if (fw_cfg_mode->is_mmio) {
+	if (fw_cfg_is_mmio) {
 		iounmap(fw_cfg_dev_base);
-		release_mem_region(fw_cfg_mode->base, fw_cfg_mode->size);
+		release_mem_region(fw_cfg_phys_base, fw_cfg_phys_size);
 	} else {
 		ioport_unmap(fw_cfg_dev_base);
-		release_region(fw_cfg_mode->base, fw_cfg_mode->size);
+		release_region(fw_cfg_phys_base, fw_cfg_phys_size);
 	}
 }
 
-/* probe and map fw_cfg device */
-static int __init fw_cfg_io_probe(void)
+/* configure fw_cfg device i/o from ACPI _CRS method */
+static acpi_status fw_cfg_walk_crs(struct acpi_resource *r, void *context)
+{
+	struct acpi_resource_io *io;
+	struct acpi_resource_fixed_memory32 *mmio;
+
+	switch (r->type) {
+	case ACPI_RESOURCE_TYPE_END_TAG:
+		return AE_OK;
+	case ACPI_RESOURCE_TYPE_IO:
+		io = &r->data.io;
+		/* physical base addr should NOT be already set */
+		if (fw_cfg_phys_base)
+			return AE_ERROR;
+		if (!request_region(io->minimum,
+				    io->address_length, "fw_cfg_io"))
+			return AE_ERROR;
+		fw_cfg_dev_base = ioport_map(io->minimum, io->address_length);
+		if (!fw_cfg_dev_base) {
+			release_region(io->minimum, io->address_length);
+			return AE_ERROR;
+		}
+		fw_cfg_phys_base = io->minimum;
+		fw_cfg_phys_size = io->address_length;
+		fw_cfg_is_mmio = false;
+		/* set register addresses (pc/i386 offsets) */
+		fw_cfg_reg_ctrl = fw_cfg_dev_base + 0x00;
+		fw_cfg_reg_data = fw_cfg_dev_base + 0x01;
+		return AE_OK;
+	case ACPI_RESOURCE_TYPE_FIXED_MEMORY32:
+		mmio = &r->data.fixed_memory32;
+		/* physical base addr should NOT be already set */
+		if (fw_cfg_phys_base)
+			return AE_ERROR;
+		/* MMIO and ACPI, but not on ARM ?!?! */
+		if (mmio->address_length < 0x0a)
+			return AE_ERROR;
+		if (!request_mem_region(mmio->address,
+					mmio->address_length, "fw_cfg_mem"))
+			return AE_ERROR;
+		fw_cfg_dev_base = ioremap(mmio->address, mmio->address_length);
+		if (!fw_cfg_dev_base) {
+			release_mem_region(mmio->address, mmio->address_length);
+			return AE_ERROR;
+		}
+		fw_cfg_phys_base = mmio->address;
+		fw_cfg_phys_size = mmio->address_length;
+		fw_cfg_is_mmio = true;
+		/* set register addresses (arm offsets) */
+		fw_cfg_reg_ctrl = fw_cfg_dev_base + 0x08;
+		fw_cfg_reg_data = fw_cfg_dev_base + 0x00;
+		return AE_OK;
+	default:
+		return AE_ERROR;
+	}
+}
+
+/* initialize fw_cfg device i/o from ACPI data */
+static int fw_cfg_acpi_init(struct acpi_device *dev)
 {
 	char sig[FW_CFG_SIG_SIZE];
+	acpi_status status;
+	int err;
 
-	for (fw_cfg_mode = &fw_cfg_modes[0];
-	     fw_cfg_mode->base; fw_cfg_mode++) {
-
-		phys_addr_t base = fw_cfg_mode->base;
-		u8 size = fw_cfg_mode->size;
-
-		/* reserve and map mmio or ioport region */
-		if (fw_cfg_mode->is_mmio) {
-			if (!request_mem_region(base, size, fw_cfg_mode->name))
-				continue;
-			fw_cfg_dev_base = ioremap(base, size);
-			if (!fw_cfg_dev_base) {
-				release_mem_region(base, size);
-				continue;
-			}
-		} else {
-			if (!request_region(base, size, fw_cfg_mode->name))
-				continue;
-			fw_cfg_dev_base = ioport_map(base, size);
-			if (!fw_cfg_dev_base) {
-				release_region(base, size);
-				continue;
-			}
-		}
+	err = acpi_bus_get_status(dev);
+	if (err < 0)
+		return err;
 
-		/* set control and data register addresses */
-		fw_cfg_reg_ctrl = fw_cfg_dev_base + fw_cfg_mode->ctrl_offset;
-		fw_cfg_reg_data = fw_cfg_dev_base + fw_cfg_mode->data_offset;
+	if (!(dev->status.enabled && dev->status.functional))
+		return -ENODEV;
 
-		/* verify fw_cfg device signature */
-		fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, 0, FW_CFG_SIG_SIZE);
-		if (memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) == 0)
-			/* success, we're done */
-			return 0;
+	/* extract device i/o details from _CRS */
+	status = acpi_walk_resources(dev->handle, METHOD_NAME__CRS,
+				     fw_cfg_walk_crs, NULL);
+	if (status != AE_OK || !fw_cfg_phys_base)
+		return -ENODEV;
 
-		/* clean up before probing next access mode */
+	/* verify fw_cfg device signature */
+	fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, 0, FW_CFG_SIG_SIZE);
+	if (memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) {
 		fw_cfg_io_cleanup();
+		return -ENODEV;
 	}
 
-	return -ENODEV;
+	return 0;
 }
 
 /* fw_cfg revision attribute, in /sys/firmware/qemu_fw_cfg top-level dir. */
@@ -353,7 +351,7 @@ static struct kobject *fw_cfg_top_ko;
 static struct kobject *fw_cfg_sel_ko;
 
 /* callback function to register an individual fw_cfg file */
-static int __init fw_cfg_register_file(const struct fw_cfg_file *f)
+static int fw_cfg_register_file(const struct fw_cfg_file *f)
 {
 	int err;
 	struct fw_cfg_sysfs_entry *entry;
@@ -397,12 +395,12 @@ static inline void fw_cfg_kobj_cleanup(struct kobject *kobj)
 	kobject_put(kobj);
 }
 
-static int __init fw_cfg_sysfs_init(void)
+static int fw_cfg_sysfs_add(struct acpi_device *dev)
 {
 	int err;
 
-	/* probe for the fw_cfg "hardware" */
-	err = fw_cfg_io_probe();
+	/* initialize fw_cfg device i/o from ACPI data */
+	err = fw_cfg_acpi_init(dev);
 	if (err)
 		return err;
 
@@ -443,14 +441,31 @@ err_top:
 	return err;
 }
 
-static void __exit fw_cfg_sysfs_exit(void)
+static int fw_cfg_sysfs_remove(struct acpi_device *dev)
 {
 	pr_debug("fw_cfg: unloading.\n");
 	fw_cfg_sysfs_cache_cleanup();
 	fw_cfg_kobj_cleanup(fw_cfg_sel_ko);
 	fw_cfg_kobj_cleanup(fw_cfg_top_ko);
 	fw_cfg_io_cleanup();
+	return 0;
 }
 
-module_init(fw_cfg_sysfs_init);
-module_exit(fw_cfg_sysfs_exit);
+static const struct acpi_device_id fw_cfg_sysfs_device_ids[] = {
+	{ "QEMU0002", 0 },
+	{ "", 0 },
+};
+MODULE_DEVICE_TABLE(acpi, fw_cfg_sysfs_device_ids);
+
+static struct acpi_driver fw_cfg_sysfs_driver = {
+	.name =		"fw_cfg",
+	.class =	"QEMU",
+	.ids =		fw_cfg_sysfs_device_ids,
+	.ops =		{
+				.add =		fw_cfg_sysfs_add,
+				.remove =	fw_cfg_sysfs_remove,
+			},
+	.owner =	THIS_MODULE,
+};
+
+module_acpi_driver(fw_cfg_sysfs_driver);
-- 
2.4.3

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