diff mbox

[2/4] PCI: quirk AMD/ATI VGA cards to avoid PM reset

Message ID 20141121182414.26669.48397.stgit@gimli.home (mailing list archive)
State New, archived
Delegated to: Bjorn Helgaas
Headers show

Commit Message

Alex Williamson Nov. 21, 2014, 6:24 p.m. UTC
Some AMD/ATI GPUs report that they support PM reset (NoSoftRst-) but
initiating such a reset has no apparent affect on the device.  The
monitor remains sync'd, the framebuffer contents are retained, etc.
Callers of pci_reset_function() don't necessarily have a way to
validate whether a reset was effective, so we really want to avoid
making use of a known non-effective reset.  Returning an error in
such cases appears to be the better option.  For users like vfio-pci,
this allows the driver to escalate to the bus reset interfaces.

If a device lives on the root bus, there's really no further
escalation path, so we exempt PM reset as potentially better than
nothing.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
---

 drivers/pci/quirks.c |   21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)


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Comments

Alex Deucher Nov. 21, 2014, 7 p.m. UTC | #1
> -----Original Message-----

> From: Alex Williamson [mailto:alex.williamson@redhat.com]

> Sent: Friday, November 21, 2014 1:24 PM

> To: bhelgaas@google.com

> Cc: linux-pci@vger.kernel.org; linux-kernel@vger.kernel.org; Alex

> Williamson; Deucher, Alexander

> Subject: [PATCH 2/4] PCI: quirk AMD/ATI VGA cards to avoid PM reset

> 

> Some AMD/ATI GPUs report that they support PM reset (NoSoftRst-) but

> initiating such a reset has no apparent affect on the device.  The

> monitor remains sync'd, the framebuffer contents are retained, etc.

> Callers of pci_reset_function() don't necessarily have a way to

> validate whether a reset was effective, so we really want to avoid

> making use of a known non-effective reset.  Returning an error in

> such cases appears to be the better option.  For users like vfio-pci,

> this allows the driver to escalate to the bus reset interfaces.

> 

> If a device lives on the root bus, there's really no further

> escalation path, so we exempt PM reset as potentially better than

> nothing.

> 

> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

> Cc: Alex Deucher <alexander.deucher@amd.com>


Acked-by: Alex Deucher <alexander.deucher@amd.com>


> ---

> 

>  drivers/pci/quirks.c |   21 +++++++++++++++++++++

>  1 file changed, 21 insertions(+)

> 

> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c

> index 90acb32..561e10d 100644

> --- a/drivers/pci/quirks.c

> +++ b/drivers/pci/quirks.c

> @@ -3008,6 +3008,27 @@

> DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_REALTEK, 0x8169,

>  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_MELLANOX, PCI_ANY_ID,

>  			 quirk_broken_intx_masking);

> 

> +static void quirk_no_pm_reset(struct pci_dev *dev)

> +{

> +	/*

> +	 * A non-effective PM reset may be better than nothing

> +	 * if we can't do a bus reset

> +	 */

> +	if (!pci_is_root_bus(dev->bus))

> +		dev->dev_flags |= PCI_DEV_FLAGS_NO_PM_RESET;

> +}

> +

> +/*

> + * Some AMD/ATI GPUS (HD8570 - Oland) report supporting PM reset via

> D3->D0

> + * transition (NoSoftRst-).  This reset mechanims seems to have no effect

> + * whatsoever on the device, even retaining the framebuffer contents and

> + * monitor sync.  Advertising this support makes other layers, like VFIO

> + * assume pci_reset_function() is viable for this device.  Mark it as

> + * unavailable to skip it when testing reset methods.

> + */

> +DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_VENDOR_ID_ATI, PCI_ANY_ID,

> +			       PCI_CLASS_DISPLAY_VGA, 8,

> quirk_no_pm_reset);

> +

>  #ifdef CONFIG_ACPI

>  /*

>   * Apple: Shutdown Cactus Ridge Thunderbolt controller.
diff mbox

Patch

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 90acb32..561e10d 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3008,6 +3008,27 @@  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_REALTEK, 0x8169,
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_MELLANOX, PCI_ANY_ID,
 			 quirk_broken_intx_masking);
 
+static void quirk_no_pm_reset(struct pci_dev *dev)
+{
+	/*
+	 * A non-effective PM reset may be better than nothing
+	 * if we can't do a bus reset
+	 */
+	if (!pci_is_root_bus(dev->bus))
+		dev->dev_flags |= PCI_DEV_FLAGS_NO_PM_RESET;
+}
+
+/*
+ * Some AMD/ATI GPUS (HD8570 - Oland) report supporting PM reset via D3->D0
+ * transition (NoSoftRst-).  This reset mechanims seems to have no effect
+ * whatsoever on the device, even retaining the framebuffer contents and
+ * monitor sync.  Advertising this support makes other layers, like VFIO
+ * assume pci_reset_function() is viable for this device.  Mark it as
+ * unavailable to skip it when testing reset methods.
+ */
+DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_VENDOR_ID_ATI, PCI_ANY_ID,
+			       PCI_CLASS_DISPLAY_VGA, 8, quirk_no_pm_reset);
+
 #ifdef CONFIG_ACPI
 /*
  * Apple: Shutdown Cactus Ridge Thunderbolt controller.