RE: [PATCH] Set PCIE maxpayload for card during hotplug insertion

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> -----Original Message-----
> From: Kenji Kaneshige [mailto:kaneshige.kenji@xxxxxxxxxxxxxx]
> Sent: Thursday, March 24, 2011 8:07 PM
> To: Hargrave, Jordan
> Cc: linux-hotplug@xxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx;
> jbarnes@xxxxxxxxxxxxxxxx
> Subject: Re: [PATCH] Set PCIE maxpayload for card during hotplug
> insertion
> 
> (2011/03/25 7:21), Jordan Hargrave wrote:
> > Reference: http://marc.info/?l=linux-hotplug&m=128932324625063&w=2
> >
> > The following patch sets the MaxPayload setting to match the parent
> reading when inserting
> > a PCIE card into a hotplug slot.  On our system, the upstream bridge
> is set to 256, but when
> > inserting a card, the card setting defaults to 128.  As soon as I/O
> is performed to the card
> > it starts receiving errors since the payload size is too small.
> >
> > Signed-off-by: Jordan_Hargrave@xxxxxxxx
> >
> > ---
> >   drivers/pci/hotplug/pcihp_slot.c |   45
> ++++++++++++++++++++++++++++++++++++++
> >   1 files changed, 45 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/pci/hotplug/pcihp_slot.c
> b/drivers/pci/hotplug/pcihp_slot.c
> > index 80b461c..912d55b 100644
> > --- a/drivers/pci/hotplug/pcihp_slot.c
> > +++ b/drivers/pci/hotplug/pcihp_slot.c
> > @@ -158,6 +158,47 @@ static void program_hpp_type2(struct pci_dev
> *dev, struct hpp_type2 *hpp)
> >   	 */
> >   }
> >
> > +/* Program PCIE MaxPayload setting on device: ensure parent
> maxpayload<= device */
> > +static int pci_set_payload(struct pci_dev *dev)
> > +{
> > +	int pos, ppos;
> > +	u16 pctl, psz;
> > +	u16 dctl, dsz, dcap, dmax;
> > +	struct pci_dev *parent;
> > +
> > +	parent = dev->bus->self;
> > +	pos = pci_find_capability(dev, PCI_CAP_ID_EXP);
> > +	if (!pos)
> > +		return 0;
> 
> You can use pci_pcie_cap(), which just returns dev->pcie_cap, instead
> of pci_find_capability().
> 
> > +
> > +	/* Read Device MaxPayload capability and setting */
> > +	pci_read_config_word(dev, pos + PCI_EXP_DEVCTL,&dctl);
> > +	pci_read_config_word(dev, pos + PCI_EXP_DEVCAP,&dcap);
> > +	dsz = (dctl&  PCI_EXP_DEVCTL_PAYLOAD)>>  5;
> > +	dmax = (dcap&  PCI_EXP_DEVCAP_PAYLOAD);
> > +
> > +	/* Read Parent MaxPayload setting */
> > +	ppos = pci_find_capability(parent, PCI_CAP_ID_EXP);
> > +	if (!ppos)
> > +		return 0;
> 
> Ditto.
> 
> > +	pci_read_config_word(parent, ppos + PCI_EXP_DEVCTL,&pctl);
> > +	psz = (pctl&   PCI_EXP_DEVCTL_PAYLOAD)>>  5;
> > +
> > +	/* If parent payload>  device max payload ->  error
> > +	 * If parent payload>  device payload ->  set speed
> > +	 * If parent payload<= device payload ->  do nothing
> > +	 */
> > +	if (psz>  dmax)
> > +		return -1;
> > +	else if (psz>  dsz) {
> 
> Maybe just "if" (not "else if") here is easier to read.
> 
> > +		dev_info(&dev->dev, "Setting MaxPayload to %d\n", 128<<
> psz);
> > +		pci_write_config_word(dev, pos + PCI_EXP_DEVCTL,
> > +				      (dctl&  ~PCI_EXP_DEVCTL_PAYLOAD) +
> > +				      (psz<<  5));
> 
> What about
> 
> 	dctrl = (dctrl & ~PCI_EXP_DEVCTL_PAYLOAD) | (psz << 5);
> 	pci_write_config_word(dev, pos + PCI_EXP_DEVCTL, dctrl);
> 
> ?
> 
> Regards,
> Kenji Kaneshige

Signed-off-by: Jordan Hargrave <Jordan_Hargrave@xxxxxxxx>
---
 drivers/pci/hotplug/pcihp_slot.c |   44 ++++++++++++++++++++++++++++++++++++++
 1 files changed, 44 insertions(+), 0 deletions(-)

diff --git a/drivers/pci/hotplug/pcihp_slot.c b/drivers/pci/hotplug/pcihp_slot.c
index 80b461c..3b628c5 100644
--- a/drivers/pci/hotplug/pcihp_slot.c
+++ b/drivers/pci/hotplug/pcihp_slot.c
@@ -158,6 +158,46 @@ static void program_hpp_type2(struct pci_dev *dev, struct hpp_type2 *hpp)
 	 */
 }
 
+/* Program PCIE MaxPayload setting on device: ensure parent maxpayload 
+<= device */ static int pci_set_payload(struct pci_dev *dev) {
+	int pos, ppos;
+	u16 pctl, psz;
+	u16 dctl, dsz, dcap, dmax;
+	struct pci_dev *parent;
+
+	parent = dev->bus->self;
+	pos = pci_pcie_cap(dev);
+	if (!pos)
+		return 0;
+
+	/* Read Device MaxPayload capability and setting */
+	pci_read_config_word(dev, pos + PCI_EXP_DEVCTL, &dctl);
+	pci_read_config_word(dev, pos + PCI_EXP_DEVCAP, &dcap);
+	dsz = (dctl & PCI_EXP_DEVCTL_PAYLOAD) >> 5;
+	dmax = (dcap & PCI_EXP_DEVCAP_PAYLOAD);
+
+	/* Read Parent MaxPayload setting */
+	ppos = pci_pcie_cap(parent);
+	if (!ppos)
+		return 0;
+	pci_read_config_word(parent, ppos + PCI_EXP_DEVCTL, &pctl);
+	psz = (pctl &  PCI_EXP_DEVCTL_PAYLOAD) >> 5;
+
+	/* If parent payload > device max payload -> error
+	 * If parent payload > device payload -> set speed
+	 * If parent payload <= device payload -> do nothing
+	 */
+	if (psz > dmax)
+		return -1;
+	if (psz > dsz) {
+		dev_info(&dev->dev, "Setting MaxPayload to %d\n", 128 << psz);
+		dctl = (dctl & ~PCI_EXP_DEVCTL_PAYLOAD) + (psz << 5);
+		pci_write_config_word(dev, pos + PCI_EXP_DEVCTL, dctl);
+	}
+	return 0;
+}
+
 void pci_configure_slot(struct pci_dev *dev)  {
 	struct pci_dev *cdev;
@@ -169,6 +209,10 @@ void pci_configure_slot(struct pci_dev *dev)
 			(dev->class >> 8) == PCI_CLASS_BRIDGE_PCI)))
 		return;
 
+	ret = pci_set_payload(dev);
+	if (ret)
+		dev_warn(&dev->dev, "could not set device max payload\n");
+
 	memset(&hpp, 0, sizeof(hpp));
 	ret = pci_get_hp_params(dev, &hpp);
 	if (ret)
--
1.7.4.1

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