firewire: ohci: fix up configuration of TI chips

On TI chips (OHCI-Lynx and later), enable link enhancements features
that TI recommends to be used.  None of these are required for proper
operation, but they are safe and nice to have.

In theory, these bits should have been set by default, but in practice,
some BIOS/EEPROM writers apparently do not read the datasheet, or get
spooked by names like "unfair".
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/ohci.c

@@ -2431,7 +2431,7 @@ static int __devinit pci_probe(struct pci_dev *dev,
 			       const struct pci_device_id *ent)
 {
 	struct fw_ohci *ohci;
-	u32 bus_options, max_receive, link_speed, version;
+	u32 bus_options, max_receive, link_speed, version, link_enh;
 	u64 guid;
 	int i, err, n_ir, n_it;
 	size_t size;
@@ -2484,6 +2484,23 @@ static int __devinit pci_probe(struct pci_dev *dev,
 	if (param_quirks)
 		ohci->quirks = param_quirks;
 
+	/* TI OHCI-Lynx and compatible: set recommended configuration bits. */
+	if (dev->vendor == PCI_VENDOR_ID_TI) {
+		pci_read_config_dword(dev, PCI_CFG_TI_LinkEnh, &link_enh);
+
+		/* adjust latency of ATx FIFO: use 1.7 KB threshold */
+		link_enh &= ~TI_LinkEnh_atx_thresh_mask;
+		link_enh |= TI_LinkEnh_atx_thresh_1_7K;
+
+		/* use priority arbitration for asynchronous responses */
+		link_enh |= TI_LinkEnh_enab_unfair;
+
+		/* required for aPhyEnhanceEnable to work */
+		link_enh |= TI_LinkEnh_enab_accel;
+
+		pci_write_config_dword(dev, PCI_CFG_TI_LinkEnh, link_enh);
+	}
+
 	ar_context_init(&ohci->ar_request_ctx, ohci,
 			OHCI1394_AsReqRcvContextControlSet);
 

drivers/firewire/ohci.h

@@ -154,4 +154,12 @@
 
 #define OHCI1394_phy_tcode		0xe
 
+/* TI extensions */
+
+#define PCI_CFG_TI_LinkEnh		0xf4
+#define  TI_LinkEnh_enab_accel		0x00000002
+#define  TI_LinkEnh_enab_unfair		0x00000080
+#define  TI_LinkEnh_atx_thresh_mask	0x00003000
+#define  TI_LinkEnh_atx_thresh_1_7K	0x00001000
+
 #endif /* _FIREWIRE_OHCI_H */