Provide a generic DRM helper that evicts all conflicting firmware
framebuffers, devices, and drivers. The new helper is called
drm_evict_firmware(), and takes a flagset controlling which firmware to
kick out.
This is meant to be used by drivers in their ->probe() callbacks of their
parent bus, before calling into drm_dev_register().
Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
---
Hey
This is just compile-tested for now. I just want to get some comments on the
design. I decided to drop the sysfb infrastructure and rather just use this
generic helper. It keeps things simple and should work just fine for all
reasonable use-cases.
This will work with SimpleDRM out-of-the-box on x86.
Architectures with dynamic simple-framebuffer devices are not supported yet. I
actually have no idea what the strategy there is? Can the DeviceTree people come
up with something? Am I supposed to call of_platform_depopulate()? Or
of_detach_node()? Or what?
Looking at drivers/of/{platform,dynamic}.c, I cannot see how this is supposed to
work at all. Who protects platform_device_del() from being called in parallel?
Also: Does any platform make use the of 'display:' entry in 'simple-framebuffer'
DT nodes? If yes, how do I get access to it? And why don't vc4/sun4i make use of
it, rather than falling back to remove_conflicting_framebuffers()?
Thanks
David
drivers/gpu/drm/drm_drv.c | 257 ++++++++++++++++++++++++++++++++++++++++++++++
include/drm/drmP.h | 13 +++
2 files changed, 270 insertions(+)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 0773547..581c342 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -26,12 +26,16 @@
* DEALINGS IN THE SOFTWARE.
*/
+#include <linux/console.h>
#include <linux/debugfs.h>
+#include <linux/fb.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/mount.h>
+#include <linux/of.h>
#include <linux/slab.h>
+#include <linux/vt.h>
#include <drm/drmP.h>
#include "drm_crtc_internal.h"
#include "drm_legacy.h"
@@ -881,6 +885,259 @@ void drm_dev_unregister(struct drm_device *dev)
}
EXPORT_SYMBOL(drm_dev_unregister);
+struct drm_evict_ctx {
+ struct apertures_struct *ap;
+ unsigned int flags;
+};
+
+static bool drm_evict_match_resource(struct drm_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 & DRM_EVICT_VBE) && mem->start == 0xA0000)
+ return true;
+ }
+
+ return false;
+}
+
+static int drm_evict_platform_device(struct device *dev, void *userdata)
+{
+ struct drm_evict_ctx *ctx = userdata;
+ struct platform_device *pdev = to_platform_device(dev);
+ struct resource *mem;
+
+ /*
+ * We are only interested in static devices here (i.e., they carry
+ * information via a statically allocated platform data field). Any
+ * dynamically allocated devices have separate ownership models and
+ * must be handled via their respective management calls.
+ */
+ if (!dev_get_platdata(&pdev->dev))
+ return 0;
+ if (!pdev->name)
+ return 0;
+
+ if (!strcmp(pdev->name, "simple-framebuffer")) {
+ mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!mem)
+ return 0;
+ if (!drm_evict_match_resource(ctx, mem))
+ return 0;
+
+ platform_device_del(pdev);
+ }
+
+ return 0;
+}
+
+static int drm_evict_platform(struct drm_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
+ * DRM 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. We
+ * must make sure our eviction callback leaves any non-static platform
+ * devices untouched, though.
+ *
+ * XXX: ARM and other OF users should really make sure to add their own
+ * eviction code here, possibly using the 'display' DT-handle as
+ * defined by the 'simple-framebuffer' OF-node.
+ */
+ mutex_lock(&lock);
+ ret = bus_for_each_dev(&platform_bus_type, NULL, ctx,
+ drm_evict_platform_device);
+ mutex_unlock(&lock);
+ return ret;
+}
+
+static int drm_evict_fbdev(struct drm_evict_ctx *ctx)
+{
+ /*
+ * We have 2 different cases where fbdev drivers can operate on the
+ * same devices as DRM drivers:
+ *
+ * o Two drivers exist for the same device, one DRM driver and one
+ * fbdev driver (e.g., nvidiafb and nouveau). In those cases, both
+ * drivers bind to the same real hw-device and driver core takes
+ * care of any conflicts.
+ *
+ * o A generic fbdev driver uses some pseudo-device to provide
+ * early-boot graphics access or some other kind of generic display
+ * driver. At the same time, a DRM driver exists that can run the
+ * real hardware (e.g., vesafb/efifb and i915).
+ *
+ * If possible, driver core takes care of any conflicts and prevents
+ * two drivers from being bound to the same device. However, in some
+ * cases this is not possible. We then use
+ * remove_conflicting_framebuffers() to match the apertures of the DRM
+ * device against all existing fbdev devices, evicting any conflicting
+ * fbdev drivers. Additionally, if requested, any VBE driver is evicted
+ * as well.
+ *
+ * Note that this breaks horribly if an fbdev driver is probed after a
+ * DRM driver. So make sure whenever such conflicts are possible, the
+ * fbdev drivers must be probed in early boot. If you cannot guarantee
+ * that, you better make sure that the driver core prevents both
+ * drivers from being probed in parallel.
+ */
+
+#if !defined(CONFIG_FB)
+ return 0;
+#else
+ return remove_conflicting_framebuffers(ctx->ap, "drm",
+ !!(ctx->flags & DRM_EVICT_VBE));
+#endif
+}
+
+static int drm_evict_vgacon(void)
+{
+ /*
+ * The VGACON console driver pokes at VGA registers randomly. If a DRM
+ * 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 DRM 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 DRM drivers, this
+ * will fail horribly. You better make sure VGACON is probed early and
+ * DRM drivers are probed as normal modules.
+ */
+
+#if !defined(CONFIG_VGA_CONSOLE)
+ return 0;
+#elif !defined(CONFIG_DUMMY_CONSOLE)
+# warning "Dummy console is disabled, but required to kick out VGACON"
+ return -ENODEV;
+#else
+ int ret = 0;
+
+ DRM_INFO("Replacing VGA console driver\n");
+
+ 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();
+
+ return ret;
+#endif
+}
+
+/**
+ * drm_evict_firmware - remove any conflicting firmware-framebuffers
+ * @ap: apertures claimed by driver, or NULL
+ * @flags: eviction flags
+ *
+ * This function evicts any conflicting firmware-framebuffers and their bound
+ * drivers, according to the data given as @ap and @flags.
+ *
+ * Depending on @flags, the following operations are performed:
+ *
+ * DRM_EVICT_FBDEV: Any fbdev drivers that overlap @ap are unloaded.
+ * Furthermore, if DRM_EVICT_VBE is given as well, any fbdev
+ * driver that maps the VGA region is unloaded.
+ *
+ * DRM_EVICT_PLATFORM: Firmware framebuffer platform devices (eg.,
+ * 'simple-framebuffer') that overlap @ap are removed
+ * from the system, causing drivers to be unbound.
+ * If DRM_EVICT_VBE is given, this also affects devices
+ * that map the VGA region.
+ *
+ * DRM_EVICT_VGACON: The vgacon console driver is unbound and unregistered.
+ *
+ * The caller must provide their apertures as @ap. If it is NULL, an empty set
+ * is assumed, except if DRM_EVICT_ANYWHERE is given, in which case a fake
+ * aperture across the entire address range is used.
+ *
+ * RETURNS:
+ * 0 on success, negative error code on failure.
+ */
+int drm_evict_firmware(struct apertures_struct *ap, unsigned int flags)
+{
+ struct drm_evict_ctx ctx;
+ struct apertures_struct *allocated_ap = NULL;
+ int ret;
+
+ WARN_ON(ap && (flags & DRM_EVICT_ANYWHERE));
+
+ if (!ap) {
+ allocated_ap = alloc_apertures(!!(flags & DRM_EVICT_ANYWHERE));
+ if (!allocated_ap)
+ return -ENOMEM;
+
+ ap = allocated_ap;
+
+ if (flags & DRM_EVICT_ANYWHERE) {
+ ap->ranges[0].base = 0;
+ ap->ranges[0].size = ~0;
+ }
+ }
+
+ ctx.ap = ap;
+ ctx.flags = flags;
+
+ if (flags & DRM_EVICT_PLATFORM) {
+ ret = drm_evict_platform(&ctx);
+ if (ret < 0)
+ return ret;
+ }
+
+ if (flags & DRM_EVICT_FBDEV) {
+ ret = drm_evict_fbdev(&ctx);
+ if (ret < 0)
+ return ret;
+ }
+
+ if (flags & DRM_EVICT_VGACON) {
+ ret = drm_evict_vgacon();
+ if (ret < 0)
+ return ret;
+ }
+
+ kfree(allocated_ap);
+ return 0;
+}
+
/*
* DRM Core
* The DRM core module initializes all global DRM objects and makes them
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 2197ab1..6c8bcf5 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -88,6 +88,7 @@ struct drm_gem_object;
struct drm_master;
struct drm_vblank_crtc;
+struct apertures_struct;
struct device_node;
struct videomode;
struct reservation_object;
@@ -971,6 +972,18 @@ void drm_dev_unref(struct drm_device *dev);
int drm_dev_register(struct drm_device *dev, unsigned long flags);
void drm_dev_unregister(struct drm_device *dev);
+enum {
+ DRM_EVICT_FBDEV = (1U << 0),
+ DRM_EVICT_PLATFORM = (1U << 1),
+ DRM_EVICT_VGACON = (1U << 2),
+ DRM_EVICT_VBE = (1U << 3),
+ DRM_EVICT_ANYWHERE = (1U << 4),
+
+ DRM_EVICT_DEFAULT = DRM_EVICT_FBDEV,
+};
+
+int drm_evict_firmware(struct apertures_struct *ap, unsigned int flags);
+
struct drm_minor *drm_minor_acquire(unsigned int minor_id);
void drm_minor_release(struct drm_minor *minor);
--
2.9.3
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