Bartlomiej,

On Wed, Jan 3, 2018 at 3:47 PM, Bartlomiej Zolnierkiewicz
[off-list ref] wrote:

On Thursday, December 21, 2017 11:07:56 PM Mathieu Malaterre wrote:

quoted

When the linux kernel is build with (typical kernel ship with Debian
installer):

CONFIG_FB_OF=y
CONFIG_VT_HW_CONSOLE_BINDING=y
CONFIG_FB_RADEON=m

The offb driver takes precedence over module radeonfb. It is then
impossible to load the module, error reported is:

[   96.551486] radeonfb 0000:00:10.0: enabling device (0006 -> 0007)
[   96.551526] radeonfb 0000:00:10.0: BAR 0: can't reserve [mem 0x98000000-0x9fffffff pref]
[   96.551531] radeonfb (0000:00:10.0): cannot request region 0.
[   96.551545] radeonfb: probe of 0000:00:10.0 failed with error -16

This patch reproduce the behavior of the module radeon, so as to make it
possible to load radeonfb when offb is first loaded.

It should be noticed that `offb_destroy` is never called which explain the
need to skip error detection on the radeon side.

This still needs to be explained more, from my last mail:

"The last put_fb_info() on fb_info should call ->fb_destroy
(offb_destroy in our case) and remove_conflicting_framebuffers()
is calling put_fb_info() so there is some extra reference on
fb_info somewhere preventing it from going away.

Please look into fixing this."

I am not familiar with the fb stuff internals but here is what I see:

# modprobe radeonfb

leads to:

[   52.058546] bus: 'pci': add driver radeonfb
[   52.058588] bus: 'pci': driver_probe_device: matched device
0000:00:10.0 with driver radeonfb
[   52.058595] bus: 'pci': really_probe: probing driver radeonfb with
device 0000:00:10.0
[   52.058608] devices_kset: Moving 0000:00:10.0 to end of list
[   52.058613] radeonfb_pci_register BEGIN
[   52.058634] radeonfb 0000:00:10.0: enabling device (0006 -> 0007)
<at this point radeon_kick_out_firmware_fb is called>
[   52.058666] checking generic (9c008000 96000) vs hw (98000000 8000000)
[   52.058667] fb: switching to radeonfb from OFfb ATY,RockHo
[   52.058844] Console: switching to colour dummy device 80x25
[   52.058860] device: 'fb0': device_unregister
[   52.058956] PM: Removing info for No Bus:fb0
[   52.059014] device: 'fb0': device_create_release
<a call to do_unregister_framebuffer is done>
<put_fb_info is done with a count=2 and dev=NULL>
[   52.059048] device: 'vtcon1': device_unregister
[   52.059076] PM: Removing info for No Bus:vtcon1
[   52.059091] device: 'vtcon1': device_create_release
[   52.059107] radeonfb 0000:00:10.0: BAR 0: can't reserve [mem
0x98000000-0x9fffffff pref]
[   52.256151] aper_base: 98000000 MC_FB_LOC to: 9bff9800, MC_AGP_LOC
to: ffffa000
[   52.256157] radeonfb (0000:00:10.0): Found 32768k of DDR 64 bits
wide videoram

I can confirm that offb_destroy is never called (not sure exactly
why), but in any case the call to radeon_kick_out_firmware_fb happen
much earlier, at least before the put_fb_info.

Could you describe a bit more the chain of calls you were thinking of ?

quoted

Signed-off-by: Mathieu Malaterre <redacted>
Link: https://bugs.debian.org/826629#57
Link: https://bugzilla.kernel.org/show_bug.cgi?id9741
Suggested-by: Lennart Sorensen <redacted>
---
v2: Only fails when CONFIG_PCC is not set
v3: Only fails when CONFIG_FB_OF is not set, CONFIG_PCC was too broad. Since the conflicts in region is due to OFfb explicitly refers to it.

It seems that there may still be configurations when this is
incorrect -> when offb drives primary (non-radeon) card and radeonfb
drives secondary (radeon) card..

quoted

 drivers/video/fbdev/aty/radeon_base.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/video/fbdev/aty/radeon_base.c b/drivers/video/fbdev/aty/radeon_base.c
index 4d77daeecf99..221879196531 100644
--- a/drivers/video/fbdev/aty/radeon_base.c
+++ b/drivers/video/fbdev/aty/radeon_base.c

@@ -2259,6 +2259,22 @@ static const struct bin_attribute edid2_attr = {
      .read   = radeon_show_edid2,
 };

+static int radeon_kick_out_firmware_fb(struct pci_dev *pdev)
+{
+     struct apertures_struct *ap;
+
+     ap = alloc_apertures(1);
+     if (!ap)
+             return -ENOMEM;
+
+     ap->ranges[0].base = pci_resource_start(pdev, 0);
+     ap->ranges[0].size = pci_resource_len(pdev, 0);
+
+     remove_conflicting_framebuffers(ap, KBUILD_MODNAME, false);
+     kfree(ap);
+
+     return 0;
+}

 static int radeonfb_pci_register(struct pci_dev *pdev,
                               const struct pci_device_id *ent)

@@ -2312,19 +2328,27 @@ static int radeonfb_pci_register(struct pci_dev *pdev,
      rinfo->fb_base_phys = pci_resource_start (pdev, 0);
      rinfo->mmio_base_phys = pci_resource_start (pdev, 2);

+     ret = radeon_kick_out_firmware_fb(pdev);
+     if (ret)
+             return ret;
+
      /* request the mem regions */
      ret = pci_request_region(pdev, 0, "radeonfb framebuffer");
      if (ret < 0) {
+#ifndef CONFIG_FB_OF
              printk( KERN_ERR "radeonfb (%s): cannot request region 0.\n",
                      pci_name(rinfo->pdev));
              goto err_release_fb;
+#endif
      }

      ret = pci_request_region(pdev, 2, "radeonfb mmio");
      if (ret < 0) {
+#ifndef CONFIG_FB_OF
              printk( KERN_ERR "radeonfb (%s): cannot request region 2.\n",
                      pci_name(rinfo->pdev));
              goto err_release_pci0;
+#endif
      }

      /* map the regions */

@@ -2509,10 +2533,12 @@ static int radeonfb_pci_register(struct pci_dev *pdev,
      iounmap(rinfo->mmio_base);
 err_release_pci2:
      pci_release_region(pdev, 2);
+#ifndef CONFIG_FB_OF
 err_release_pci0:
      pci_release_region(pdev, 0);
 err_release_fb:
         framebuffer_release(info);
+#endif
 err_disable:
 err_out:
      return ret;

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

Thanks,
-M