[PATCH net-next 1/2] net: sgi: ioc3-eth: apply the DMA attributes only to 64-bit addresses

[Imre Kaloz <kaloz@kernel.org>]

A Bridge 64-bit direct-mapped DMA address carries the target widget and
the DMA attributes. An address in the 2GB 32-bit direct window carries
neither, so attributes OR-ed onto one aim it at widget 0, and every
receive raises a PCI error.

Apply them, and the RX barrier's upper address bits, only to 64-bit
addresses. IP27 and IP30 give the IOC3 64-bit addresses; behind an
XBridge or PIC it can use the window.

Signed-off-by: Imre Kaloz <kaloz@kernel.org>
---
Previously posted as 25/53 of the IP35 series v2: https://lore.kernel.org/all/cover.1791890466.git.kaloz@kernel.org/

 drivers/net/ethernet/sgi/ioc3-eth.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/sgi/ioc3-eth.c b/drivers/net/ethernet/sgi/ioc3-eth.c
index 009f37105eaf..25139cf5ff62 100644
--- a/drivers/net/ethernet/sgi/ioc3-eth.c
+++ b/drivers/net/ethernet/sgi/ioc3-eth.c
@@ -152,19 +152,37 @@ static inline int ioc3_alloc_skb(struct ioc3_private *ip, struct sk_buff **skb,
 }
 
 #ifdef CONFIG_PCI_XTALK_BRIDGE
+/* A Bridge 64-bit direct-mapped DMA address carries the target widget in
+ * bits 63:60 and the DMA attributes below it.  An address in the 32-bit
+ * direct window carries neither, so attributes OR-ed onto one form a
+ * 64-bit address aimed at widget 0.
+ */
 static inline unsigned long ioc3_map(dma_addr_t addr, unsigned long attr)
 {
+	if (!(addr & PCI64_ATTR_TARG_MASK))
+		return addr;
+
 	return (addr & ~PCI64_ATTR_BAR) | attr;
 }
 
-#define ERBAR_VAL	(ERBAR_BARRIER_BIT << ERBAR_RXBARR_SHIFT)
+/* The RX barrier's upper address bits follow the same form. */
+static inline u32 ioc3_erbar(dma_addr_t addr)
+{
+	if (!(addr & PCI64_ATTR_TARG_MASK))
+		return 0;
+
+	return ERBAR_BARRIER_BIT << ERBAR_RXBARR_SHIFT;
+}
 #else
 static inline unsigned long ioc3_map(dma_addr_t addr, unsigned long attr)
 {
 	return addr;
 }
 
-#define ERBAR_VAL	0
+static inline u32 ioc3_erbar(dma_addr_t addr)
+{
+	return 0;
+}
 #endif
 
 static int ioc3eth_nvmem_match(struct device *dev, const void *data)
@@ -727,7 +745,7 @@ static void ioc3_init(struct net_device *dev)
 	readl(&regs->emcr);
 
 	/* Misc registers  */
-	writel(ERBAR_VAL, &regs->erbar);
+	writel(ioc3_erbar(ip->rxr_dma), &regs->erbar);
 	readl(&regs->etcdc);			/* Clear on read */
 	writel(15, &regs->ercsr);		/* RX low watermark  */
 	writel(0, &regs->ertr);			/* Interrupt immediately */
-- 
2.47.3