linux-kernel - Re: [PATCH v3] Fix loading of module radeonfb on PowerMac

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Date:   Wed, 03 Jan 2018 15:47:35 +0100
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     Mathieu Malaterre <malat@...ian.org>
Cc:     Tomi Valkeinen <tomi.valkeinen@...com>,
        Lennart Sorensen <lsorense@...lub.uwaterloo.ca>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] Fix loading of module radeonfb on PowerMac


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

> Signed-off-by: Mathieu Malaterre <malat@...ian.org>
> Link: https://bugs.debian.org/826629#57
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=119741
> Suggested-by: Lennart Sorensen <lsorense@...lub.uwaterloo.ca>
> ---
> 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..

>  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