linux-kernel - Re: [Patch v2] apple-gmux: lock iGP IO to protect from vgaarb changes

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Message-ID: <20150307011546.0050279d@neptune.home>
Date:	Sat, 7 Mar 2015 01:15:46 +0100
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	Darren Hart <dvhart@...radead.org>
Cc:	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	Petri Hodju <petrihodju@...oo.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Matthew Garrett <matthew.garrett@...ula.com>
Subject: Re: [Patch v2] apple-gmux: lock iGP IO to protect from vgaarb
 changes

On Fri, 06 March 2015 Darren Hart <dvhart@...radead.org> wrote:
> On Thu, Mar 05, 2015 at 11:20:38PM +0100, Bruno Prémont wrote:
> > As GMUX depends on IO for iGP to be enabled and active, lock the IO at
> > vgaarb level. This should prevent GPU driver for dGPU to disable IO for
> > iGP while it tries to own legacy VGA IO.
> > 
> > This fixes usage of backlight control combined with closed nvidia
> > driver on some Apple dual-GPU (intel/nvidia) systems.
> > 
> > On those systems loading nvidia driver disables intel IO decoding,
> > disabling the gmux backlight controls as a side effect.
> > Prior to commits moving boot_vga from (optional) efifb to less optional
> > vgaarb this mis-behavior could be avoided by using right kernel config
> > (efifb enabled but vgaarb disabled).
> > 
> > This patch explicitly does not try to trigger vgaarb changes in order
> > to avoid confusing already running graphics drivers. If IO has been
> > mis-configured by vgaarb gmux will thus fail to probe.
> > It is expected to load/probe gmux prior to graphics drivers.
> > 
> > Fixes: ce027dac592c0ada241ce0f95ae65856828ac450 # nvidia interaction
> > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=86121
> > Reported-by: Petri Hodju <petrihodju@...oo.com>
> > Tested-by: Petri Hodju <petrihodju@...oo.com>
> > Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> > Cc: Matthew Garrett <matthew.garrett@...ula.com>
> > Signed-off-by: Bruno Prémont <bonbons@...ux-vserver.org>
> > ---
> > Respinning, fixing Darren's nit.
> > 
> > Changes since v1:
> > - Dropped repeat of gmux in pr_info/pr_err calls
> > - Mention PCI device we tried to lock IO for in case of error

Hi Darren,

> Hi Bruno,
> 
> I don't know if this is on your end or mine (I've not seen this before). Saving
> off your patch (through mutt like I do everything else) to a file and applying
> works, build works, and git show and visual inspection look correct.
> 
> However, checkpatch sees a lot of =3D instead of just =, and complains bitterly.
> 
> Can you check this patch (from the list) and let me know what you find?

That smells like `Content-Transfer-Encoding: quoted-printable` not being
understood by check-patch when operating on a raw mail.
No idea if mutt can recode the mail to plain 8-bit/UTF-8 when saving...
patch from patch-utils might have the same issues with it while git-am is
fine (as it handles mail-patches including charset and other headers).

I'm sending the mail via claws-mail which might encode it more
conservatively than e.g. git-send-email. I can see if there's an option
to prefer 8-bit over quoted-printable though.

Bruno


> ERROR: patch seems to be corrupt (line wrapped?)
> #93: FILE: drivers/platform/x86/apple-gmux.c:27:
> =20
> 
> ERROR: spaces required around that '=' (ctx:WxV)
> #108: FILE: drivers/platform/x86/apple-gmux.c:421:
> +	struct pci_dev *pdev =3D NULL;
>  	                     ^
> 
> WARNING: Missing a blank line after declarations
> #109: FILE: drivers/platform/x86/apple-gmux.c:422:
> +	struct pci_dev *pdev =3D NULL;
> +	while ((pdev =3D pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, pdev))) {
> 
> ERROR: spaces required around that '=' (ctx:WxV)
> #109: FILE: drivers/platform/x86/apple-gmux.c:422:
> +	while ((pdev =3D pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, pdev))) {
>  	             ^
> 
> ERROR: spaces required around that '=' (ctx:WxV)
> #130: FILE: drivers/platform/x86/apple-gmux.c:447:
> +	struct pci_dev *pdev =3D NULL;
>  	                     ^
> 
> ERROR: spaces required around that '=' (ctx:WxV)
> #155: FILE: drivers/platform/x86/apple-gmux.c:510:
> +	pdev =3D gmux_find_pdev();
>  	     ^
> 
> ERROR: spaces required around that '=' (ctx:WxV)
> #160: FILE: drivers/platform/x86/apple-gmux.c:515:
> +		ret =3D -EBUSY;
>  		    ^
> 
> ERROR: need consistent spacing around '-' (ctx:WxV)
> #160: FILE: drivers/platform/x86/apple-gmux.c:515:
> +		ret =3D -EBUSY;
>  		        ^
> 
> ERROR: spaces required around that '=' (ctx:WxV)
> #164: FILE: drivers/platform/x86/apple-gmux.c:519:
> +	gmux_data->pdev =3D pdev;
>  	                ^
> 
> total: 8 errors, 1 warnings, 96 lines checked
> 
> /home/dvhart/apple.patch has style problems, please review.
> 
> If any of these errors are false positives, please report
> them to the maintainer, see CHECKPATCH in MAINTAINERS.
> 
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