linux-kernel - RE: [PATCH V2] Quirk for IVB graphics FLR errata

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Date:	Thu, 1 Mar 2012 01:25:32 +0000
From:	"Hao, Xudong" <xudong.hao@...el.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"Kay, Allen M" <allen.m.kay@...el.com>,
	"Zhang, Xiantao" <xiantao.zhang@...el.com>
Subject: RE: [PATCH V2] Quirk for IVB graphics FLR errata

> -----Original Message-----
> From: Jesse Barnes [mailto:jbarnes@...tuousgeek.org]
> Sent: Thursday, March 01, 2012 2:32 AM
> To: Hao, Xudong
> Cc: linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org;
> kvm@...r.kernel.org; Kay, Allen M; Zhang, Xiantao
> Subject: Re: [PATCH V2] Quirk for IVB graphics FLR errata
> 
> On Wed, 29 Feb 2012 03:11:24 +0000
> "Hao, Xudong" <xudong.hao@...el.com> wrote:
> 
> > For IvyBridge Mobile platform, a system hang may occur if a
> > FLR(Function Level Reset) is asserted to internal graphics.
> >
> > This quirk patch is workaround for the IVB FLR errata issue.
> > We are disabling the FLR reset handshake between the PCH and CPU
> > display, then manually powering down the panel power sequencing and
> > resetting the PCH display.
> >
> > Signed-off-by: Xudong Hao <xudong.hao@...el.com>
> > Signed-off-by: Kay, Allen M <allen.m.kay@...el.com>
> > ---
> >  drivers/pci/quirks.c |   49
> > +++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed,
> 49
> > insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c index
> > 6476547..5223b80 100644 --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -29,6 +29,11 @@
> >  #include <asm/dma.h>	/* isa_dma_bridge_buggy */
> >  #include "pci.h"
> >
> > +#include "../gpu/drm/i915/i915_reg.h"
> 
> Ugg... this is ugly.  Should probably go near the definition of the quirk at any
> rate.
> 

OK, I'll move it just above the reset_ivb_igd function.

> > +#include <asm/tsc.h>
> > +/* 10 seconds */
> > +#define IGD_OPERATION_TIMEOUT ((cycles_t) tsc_khz*10*1000)
> > +
> 
> Same here, the asm/tsc.h can go at the top, but the timeout definition should
> go near the reset function.
> 
> May as well make it a static const cycles_t as well.
> 
Will modify it.
 
> > +#define MSG_CTL	0x45010
> > +
> > +static int reset_ivb_igd(struct pci_dev *dev, int probe) {
> > +	u8 *mmio_base;
> > +	u32 val;
> > +
> > +	if (probe)
> > +		return 0;
> > +
> > +	mmio_base = ioremap_nocache(pci_resource_start(dev, 0),
> > +				 pci_resource_len(dev, 0));
> > +	if (!mmio_base)
> > +		return -ENOMEM;
> > +
> > +	/* Work Around */
> > +	*((u32 *)(mmio_base + MSG_CTL)) = 0x00000002;
> > +	*((u32 *)(mmio_base + SOUTH_CHICKEN2)) = 0x00000005;
> > +	val = *((u32 *)(mmio_base + PCH_PP_CONTROL)) & 0xfffffffe;
> > +	*((u32 *)(mmio_base + PCH_PP_CONTROL)) = val;
> 
> These clobber existing values.  Since we're doing a reset, clobbering
> PCH_PP_CONTROL should be ok, but clobbering SOUTH_CHICKEN2 is only ok if
> the next driver that loads sets the right bits (if i915 was previously using the
> device, it would have set a couple of bits).
> 
> But again since it's it a reset that's probably ok, but you should put a comment
> indicating as much.
> 

I'll add comment here, thanks Jesse.

> > +	do {
> > +		cycles_t start_time = get_cycles();
> > +		while (1) {
> > +			val = *((u32 *)(mmio_base + PCH_PP_STATUS));
> > +			if (((val & 0x80000000) == 0)
> > +				&& ((val & 0x30000000) == 0))
> > +				break;
> > +			if (IGD_OPERATION_TIMEOUT < (get_cycles() -
> > start_time))
> > +				break;
> > +			cpu_relax();
> > +		}
> > +	} while (0);
> > +	*((u32 *)(mmio_base + 0xd0100)) = 0x00000002;
> > +
> > +	iounmap(pci_resource_start(dev, 0));
> > +	return 0;
> > +}
> > +
> >  #define PCI_DEVICE_ID_INTEL_82599_SFP_VF   0x10ed
> > +#define PCI_DEVICE_ID_INTEL_IVB_M_VGA      0x0156
> > +#define PCI_DEVICE_ID_INTEL_IVB_M2_VGA     0x0166
> >
> >  static const struct pci_dev_reset_methods pci_dev_reset_methods[] = {
> >  	{ PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82599_SFP_VF,
> >  		 reset_intel_82599_sfp_virtfn },
> > +	{ PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_IVB_M_VGA,
> > +		reset_ivb_igd },
> > +	{ PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_IVB_M2_VGA,
> > +		reset_ivb_igd },
> >  	{ PCI_VENDOR_ID_INTEL, PCI_ANY_ID,
> >  		reset_intel_generic_dev },
> >  	{ 0 }
> 
> Looks ok otherwise, thanks.
> 
> Jesse
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