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

[Noralf Trønnes]

Den 02.09.2016 10:22, skrev David Herrmann:
> 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 at 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")) {

This doesn't work in my case where the device comes from DT and the name
also contains the address: pdev->name=1e887000.framebuffer

This is one way of solving it:

        if (!pdev->dev.driver || !pdev->dev.driver->name)
                 return 0;

        if (!strcmp(pdev->dev.driver->name, "simple-framebuffer")) {


Noralf.

> +		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 */