On Wed, 04 Jun 2014, David Herrmann [off-list ref] wrote:

Hi

On Wed, Jun 4, 2014 at 12:57 AM, Daniel Vetter [off-list ref] wrote:

quoted

From: Chris Wilson <redacted>

Touching the VGA resources on an IVB EFI machine causes hard hangs when
we then kick out the efifb. Ouch.

Apparently this also prevents unclaimed register errors on hsw and
hard machine hangs on my i855gm when trying to unbind fbcon.

Also, we want this to make I915_FBDEV=n safe.

v2: Rebase and pimp commit message.

v3: We also need to unregister the vga console, otherwise the unbind
of the fb console before module unload might resurrect it again.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?idg813
Cc: David Herrmann <redacted>
Cc: Jean-Christophe Plagniol-Villard <redacted>
Cc: Tomi Valkeinen <redacted>
Cc: linux-fbdev@vger.kernel.org
Signed-off-by: Chris Wilson <redacted> (v1)
Signed-off-by: Daniel Vetter <redacted>
---
 drivers/gpu/drm/i915/i915_dma.c  | 34 +++++++++++++++++++++++++++++++++-
 drivers/video/console/dummycon.c |  1 +
 drivers/video/console/vgacon.c   |  1 +
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index b9159ade5e85..a4df80740b37 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c

@@ -36,6 +36,8 @@
 #include "i915_drv.h"
 #include "i915_trace.h"
 #include <linux/pci.h>
+#include <linux/console.h>
+#include <linux/vt.h>
 #include <linux/vgaarb.h>
 #include <linux/acpi.h>
 #include <linux/pnp.h>

@@ -1450,6 +1452,29 @@ static void i915_kick_out_firmware_fb(struct drm_i915_private *dev_priv)
 }
 #endif

+static int i915_kick_out_vgacon(struct drm_i915_private *dev_priv)
+{
+#if !defined(CONFIG_VGA_CONSOLE)
+       return 0;
+#else
+       int ret;
+
+#if !defined(CONFIG_DUMMY_CONSOLE)
+       return -ENODEV;
+#endif
+
+       DRM_INFO("Replacing VGA console driver\n");
+
+       console_lock();
+       ret = do_take_over_console(&dummy_con, 0, MAX_NR_CONSOLES - 1, 1);

You rely on compiler-optimizations here. "dummy_con" is not available
if !CONFIG_DUMMY_CONSOLE, but you use it. This causes linker-failure
if dead-code elimination is not done (-O0).

Nested #ifs too. How about

#if !defined(CONFIG_VGA_CONSOLE)
static inline int i915_kick_out_vgacon(struct drm_i915_private *dev_priv)
{
	return 0;
}
#elif !defined(CONFIG_DUMMY_CONSOLE)
static inline int i915_kick_out_vgacon(struct drm_i915_private *dev_priv)
{
	return -ENODEV;
}
#else
static int i915_kick_out_vgacon(struct drm_i915_private *dev_priv)
{
	/* ... */
}
#endif

in proper kernel style?

BR,
Jani.

Thanks
David

quoted

+       if (ret = 0)
+               ret = do_unregister_con_driver(&vga_con);
+       console_unlock();
+
+       return ret;
+#endif
+}
+
 static void i915_dump_device_info(struct drm_i915_private *dev_priv)
 {
        const struct intel_device_info *info = &dev_priv->info;

@@ -1623,8 +1648,15 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
        if (ret)
                goto out_regs;

-       if (drm_core_check_feature(dev, DRIVER_MODESET))
+       if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+               ret = i915_kick_out_vgacon(dev_priv);
+               if (ret) {
+                       DRM_ERROR("failed to remove conflicting VGA console\n");
+                       goto out_gtt;
+               }
+
                i915_kick_out_firmware_fb(dev_priv);
+       }

        pci_set_master(dev->pdev);

diff --git a/drivers/video/console/dummycon.c b/drivers/video/console/dummycon.c
index b63860f7beab..40bec8d64b0a 100644
--- a/drivers/video/console/dummycon.c
+++ b/drivers/video/console/dummycon.c

@@ -77,3 +77,4 @@ const struct consw dummy_con = {
     .con_set_palette = DUMMY,
     .con_scrolldelta = DUMMY,
 };
+EXPORT_SYMBOL_GPL(dummy_con);

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 9d8feac67637..84acd6223dc5 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c

@@ -1440,5 +1440,6 @@ const struct consw vga_con = {
        .con_build_attr = vgacon_build_attr,
        .con_invert_region = vgacon_invert_region,
 };
+EXPORT_SYMBOL(vga_con);

 MODULE_LICENSE("GPL");
--

1.8.1.4

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-- 
Jani Nikula, Intel Open Source Technology Center