[PATCH v5 4/7] video: add generic framebuffer eviction

[David Herrmann <dh.herrmann@gmail.com>]

There are several situations where we want hardware handover from an early
boot GFX driver (e.g., vgacon, vesafb, efifb, simplefb) to a full fletched
GFX driver (e.g., most DRM drivers). So far, we relied on
remove_conflicting_framebuffers() to do this for us, however, this had a
bunch of downsides:

  o It only removes conflicting fbdev drivers. It does not drop vgacon,
    early boot console drivers, conflicting DRM drivers, etc.

  o It only unloads the fbdev driver, it does not modify the underlying
    device or resources. In case of "screen_info" drivers (e.g., efifb)
    this is fine, since no resources are pinned. However, if the driver
    binds to a platform-device like "simple-framebuffer", we must make
    sure to unregister that device as well. Otherwise, pinned resources
    like IORESOURCE_MEM stay around, triggering WARN_ONs if the following
    driver requests those resources.

  o It is only available if CONFIG_FB is selected.

This commit adds a new infrastructure that manages system-framebuffers
(short: sysfb). The initial commit provides conflict-resolution for
system-framebuffers. At its core it provides sysfb_evict_conflicts(),
which implements conflict detection and removal for all known types of
GFX driver hand-overs. So far, this includes platform-device removal,
fbdev-firmware-device removal, vgacon removal and VBE detection. To
further simplify the callers, it also provides helpers to figure out what
hand-over to do, based on the device the new drivers binds to:

  o PCI drivers can use sysfb_evict_conflicts_pci(), which will figure out
    the apertures automatically, and does VGA/VBE detection.

  o Generic firmware drivers that might be shadowed at any address in
    memory can use sysfb_evict_conflicts_firmware(), basically removing
    *all* firmware framebuffers in effect.

This only adds the generic sysfb helpers. No users are converted, yet.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
---
 drivers/video/Kconfig  |   4 +
 drivers/video/Makefile |   1 +
 drivers/video/sysfb.c  | 327 +++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/sysfb.h  |  34 +++++
 4 files changed, 366 insertions(+)
 create mode 100644 drivers/video/sysfb.c
 create mode 100644 include/linux/sysfb.h

diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 3c20af9..56a8294 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -36,6 +36,10 @@ config VIDEOMODE_HELPERS
 config HDMI
 	bool
 
+config SYSFB
+	bool
+	select DUMMY_CONSOLE if VT
+
 if VT
 	source "drivers/video/console/Kconfig"
 endif
diff --git a/drivers/video/Makefile b/drivers/video/Makefile
index 9ad3c17..df7bd75 100644
--- a/drivers/video/Makefile
+++ b/drivers/video/Makefile
@@ -1,5 +1,6 @@
 obj-$(CONFIG_VGASTATE)            += vgastate.o
 obj-$(CONFIG_HDMI)                += hdmi.o
+obj-$(CONFIG_SYSFB)		  += sysfb.o
 
 obj-$(CONFIG_VT)		  += console/
 obj-$(CONFIG_LOGO)		  += logo/
diff --git a/drivers/video/sysfb.c b/drivers/video/sysfb.c
new file mode 100644
index 0000000..00585c9
--- /dev/null
+++ b/drivers/video/sysfb.c
@@ -0,0 +1,327 @@
+/*
+ * Copyright (C) 2013-2016 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ */
+
+#define pr_fmt(fmt) "sysfb: " fmt
+#include <linux/console.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/fb.h>
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/pci.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/sysfb.h>
+#include <linux/vt.h>
+
+static bool sysfb_evict_match_resource(struct sysfb_evict_ctx *ctx,
+				       struct resource *mem)
+{
+	struct aperture *g;
+	unsigned int i;
+
+	for (i = 0; i < ctx->ap->count; ++i) {
+		g = &ctx->ap->ranges[i];
+
+		if (mem->start == g->base)
+			return true;
+		if (mem->start >= g->base && mem->end < g->base + g->size)
+			return true;
+		if ((ctx->flags & SYSFB_EVICT_VBE) && mem->start == 0xA0000)
+			return true;
+	}
+
+	return false;
+}
+
+static int sysfb_evict_platform_device(struct device *dev, void *userdata)
+{
+	struct sysfb_evict_ctx *ctx = userdata;
+	struct platform_device *pdev = to_platform_device(dev);
+	struct resource *mem;
+
+	if (!pdev->name)
+		return 0;
+
+	if (!strcmp(pdev->name, "simple-framebuffer")) {
+		mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+		if (!mem)
+			return 0;
+		if (!sysfb_evict_match_resource(ctx, mem))
+			return 0;
+
+#ifdef CONFIG_OF_ADDRESS
+		if (dev->of_node)
+			of_platform_device_destroy(dev);
+		else
+#endif
+		if (dev_get_platdata(&pdev->dev))
+			platform_device_del(pdev);
+	}
+
+	return 0;
+}
+
+static int sysfb_evict_platform(struct sysfb_evict_ctx *ctx)
+{
+	/*
+	 * Early-boot architecture setup and boot-loarders sometimes create
+	 * preliminary platform devices with a generic framebuffer setup. This
+	 * allows graphics access during boot-up, without a real graphics
+	 * driver loaded. However, once a real graphics driver takes over, we
+	 * have to destroy those platform devices. In the legacy fbdev case, we
+	 * just used to unload the fbdev driver. However, to make sure any kind
+	 * of driver is unloaded, the platform-eviction code here simply
+	 * removes any conflicting platform device directly. This causes any
+	 * bound driver to be detached, and then removes the device entirely so
+	 * it cannot be bound to later on.
+	 *
+	 * Please note that any such platform device must be registered by
+	 * early architecture setup code. If they are registered after regular
+	 * GFX drivers, this will fail horribly.
+	 */
+
+	static DEFINE_MUTEX(lock);
+	int ret;
+
+	/*
+	 * In case of static platform-devices, we must iterate the bus and
+	 * remove them manually. We know that we're the only code that might
+	 * remove them, so a simple static lock serializes all calls here.
+	 */
+	mutex_lock(&lock);
+	ret = bus_for_each_dev(&platform_bus_type, NULL, ctx,
+			       sysfb_evict_platform_device);
+	mutex_unlock(&lock);
+	return ret;
+}
+
+static int sysfb_evict_fbdev(struct sysfb_evict_ctx *ctx)
+{
+	/*
+	 * Usually, evicting platform devices should be enough to also trigger
+	 * fbdev unloading. However, some legacy devices (e.g., uvesafb) have
+	 * no platform devices that can be evicted, so we still fall back to
+	 * the legacy fbdev removal code. Note that this only removes fbdev
+	 * devices marked as FBINFO_MISC_FIRMWARE. Anything else is left
+	 * untouched.
+	 *
+	 * As usual, this only works if the fbdev device is probed early,
+	 * before any real GFX driver wants to take over.
+	 */
+
+	int ret = 0;
+
+#ifdef CONFIG_FB
+	ret = remove_conflicting_framebuffers(ctx->ap, "sysfb",
+					      ctx->flags & SYSFB_EVICT_VBE);
+#endif
+
+	return ret;
+}
+
+static int sysfb_evict_vgacon(struct sysfb_evict_ctx *ctx)
+{
+	/*
+	 * The VGACON console driver pokes at VGA registers randomly. If a GFX
+	 * driver cannot keep the VGA support alive, it better makes sure to
+	 * unload VGACON before probing.
+	 *
+	 * Unloading VGACON requires us to first force dummycon to take over
+	 * from vgacon (but only if vgacon is really in use), followed by a
+	 * deregistration of vgacon. Note that this prevents vgacon from being
+	 * used again after the GFX driver is unloaded. But that is usually
+	 * fine, since VGA state is rarely restored on driver-unload, anyway.
+	 *
+	 * Note that we rely on VGACON to be probed in early boot (actually
+	 * done by ARCH setup code). If it is probed after GFX drivers, this
+	 * will fail horribly. You better make sure VGACON is probed early and
+	 * GFX drivers are probed as normal modules.
+	 */
+
+	int ret = 0;
+
+#ifdef CONFIG_VGA_CONSOLE
+	console_lock();
+	if (con_is_bound(&vga_con))
+		ret = do_take_over_console(&dummy_con, 0,
+					   MAX_NR_CONSOLES - 1, 1);
+	if (ret == 0) {
+		ret = do_unregister_con_driver(&vga_con);
+		if (ret == -ENODEV) /* ignore "already unregistered" */
+			ret = 0;
+	}
+	console_unlock();
+#endif
+
+	return ret;
+}
+
+/**
+ * sysfb_evict_conflicts - remove any conflicting system-framebuffers
+ * @ctx:		eviction context
+ *
+ * This function evicts any conflicting system-framebuffers and their bound
+ * drivers, according to the data given in @ctx.
+ *
+ * Depending on @ctx->flags, the following operations are performed:
+ *
+ *   SYSFB_EVICT_PLATFORM: Firmware framebuffer platform devices (eg.,
+ *                         'simple-framebuffer') that overlap @ctx are removed
+ *                         from the system, causing drivers to be unbound.
+ *                         If SYSFB_EVICT_VBE is given, this also affects
+ *                         devices that own the VGA region.
+ *
+ *   SYSFB_EVICT_FBDEV: Any firmware fbdev drivers that overlap @ctx are
+ *                      unloaded.
+ *                      Furthermore, if SYSFB_EVICT_VBE is given as well, any
+ *                      fbdev driver that maps the VGA region is unloaded.
+ *
+ *   SYSFB_EVICT_VGACON: The vgacon console driver is unbound and unregistered.
+ *
+ * This might call into fbdev driver unregistration, or even device_del() on
+ * some buses. Hence, make sure you call this from your top-level
+ * probe-callbacks, rather than with any gfx-subsystem locks held.
+ *
+ * RETURNS:
+ * 0 on success, negative error code on failure.
+ */
+int sysfb_evict_conflicts(struct sysfb_evict_ctx *ctx)
+{
+	int ret;
+
+	if (WARN_ON(!ctx || !ctx->ap))
+		return -EINVAL;
+
+	pr_info("removing conflicts (sysfb%s%s%s%s)\n",
+		(ctx->flags & SYSFB_EVICT_PLATFORM) ? ", platform" : "",
+		(ctx->flags & SYSFB_EVICT_FBDEV) ? ", fbdev" : "",
+		(ctx->flags & SYSFB_EVICT_VGACON) ? ", vgacon" : "",
+		(ctx->flags & SYSFB_EVICT_VBE) ? ", vbe" : "");
+
+	if (ctx->flags & SYSFB_EVICT_PLATFORM) {
+		ret = sysfb_evict_platform(ctx);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (ctx->flags & SYSFB_EVICT_FBDEV) {
+		ret = sysfb_evict_fbdev(ctx);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (ctx->flags & SYSFB_EVICT_VGACON) {
+		ret = sysfb_evict_vgacon(ctx);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(sysfb_evict_conflicts);
+
+/**
+ * sysfb_evict_conflicts_firmware() - remove all firmware framebuffers
+ *
+ * This is similar to sysfb_evict_conflicts() but uses a fake aperture spanning
+ * the entire address-space. This is suitable for any GFX driver that just
+ * wants to get rid of all available firmware framebuffers.
+ *
+ * RETURNS:
+ * 0 on success, negative error code on failure.
+ */
+int sysfb_evict_conflicts_firmware(void)
+{
+	struct sysfb_evict_ctx ctx = {};
+	int ret;
+
+	ctx.ap = alloc_apertures(1);
+	if (!ctx.ap)
+		return -ENOMEM;
+
+	ctx.ap->ranges[0].base = 0;
+	ctx.ap->ranges[0].size = ~0;
+
+	ctx.flags |= SYSFB_EVICT_FBDEV | SYSFB_EVICT_PLATFORM;
+	ret = sysfb_evict_conflicts(&ctx);
+
+	kfree(ctx.ap);
+	return ret;
+}
+EXPORT_SYMBOL(sysfb_evict_conflicts_firmware);
+
+#ifdef CONFIG_PCI
+/**
+ * sysfb_evict_conflicts_pci() - remove all system framebuffers conflicting
+ *                               with the given pci device
+ * @pdev:		pci device
+ *
+ * This is similar to sysfb_evict_conflicts() but generates the eviction
+ * context based on the given pci device @pdev.
+ *
+ * RETURNS:
+ * 0 on success, negative error code on failure.
+ */
+int sysfb_evict_conflicts_pci(struct pci_dev *pdev)
+{
+	struct sysfb_evict_ctx ctx = {};
+	size_t i, n, offset;
+	int ret;
+
+	/*
+	 * If this device is used as primary VGA device, it is shadowed at the
+	 * VBE base address, so make sure to include it in the apertures.
+	 */
+	if (pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW)
+		ctx.flags |= SYSFB_EVICT_VBE;
+
+	/*
+	 * If a device is a VGA device, make sure to kick out vgacon. We cannot
+	 * rely on the IORESOURCE_ROM_SHADOW, since vgacon can switch between
+	 * vga devices at runtime. So kick out vgacon anyway.
+	 */
+	if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
+		ctx.flags |= SYSFB_EVICT_VGACON;
+
+	/*
+	 * Allocate apertures for all standard PCI resources. Skip them in case
+	 * they are empty.
+	 */
+	ctx.ap = alloc_apertures(PCI_STD_RESOURCE_END - PCI_STD_RESOURCES + 1);
+	if (!ctx.ap)
+		return -ENOMEM;
+
+	offset = PCI_STD_RESOURCES;
+	for (n = 0, i = 0; i < ctx.ap->count; ++i) {
+		if (pci_resource_len(pdev, offset + i) < 1)
+			continue;
+
+		ctx.ap->ranges[n].base = pci_resource_start(pdev, offset + i);
+		ctx.ap->ranges[n].size = pci_resource_len(pdev, offset + i);
+		++n;
+	}
+	ctx.ap->count = n;
+
+	/*
+	 * Evict all matching fbdev devices, VBE devices if they shadow this
+	 * device, vgacon if this is a vga device, and platform devices if they
+	 * match.
+	 */
+	ctx.flags |= SYSFB_EVICT_FBDEV | SYSFB_EVICT_PLATFORM;
+	ret = sysfb_evict_conflicts(&ctx);
+
+	kfree(ctx.ap);
+	return ret;
+}
+EXPORT_SYMBOL(sysfb_evict_conflicts_pci);
+#endif /* CONFIG_PCI */
diff --git a/include/linux/sysfb.h b/include/linux/sysfb.h
new file mode 100644
index 0000000..b67c74a
--- /dev/null
+++ b/include/linux/sysfb.h
@@ -0,0 +1,34 @@
+#ifndef __LINUX_SYSFB_H
+#define __LINUX_SYSFB_H
+
+/*
+ * Copyright (C) 2013-2016 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/kernel.h>
+
+struct apertures_struct;
+struct pci_dev;
+
+enum {
+	SYSFB_EVICT_PLATFORM			= (1U <<  0),
+	SYSFB_EVICT_FBDEV			= (1U <<  1),
+	SYSFB_EVICT_VGACON			= (1U <<  2),
+	SYSFB_EVICT_VBE				= (1U <<  3),
+};
+
+struct sysfb_evict_ctx {
+	struct apertures_struct *ap;
+	unsigned int flags;
+};
+
+int sysfb_evict_conflicts(struct sysfb_evict_ctx *ctx);
+int sysfb_evict_conflicts_firmware(void);
+int sysfb_evict_conflicts_pci(struct pci_dev *pdev);
+
+#endif /* __LINUX_SYSFB_H */
-- 
2.9.3

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