[U-Boot] [PATCH v2] drivers/net/designware - fix alignment of buffer descriptors

[Alexey Brodkin]

It's important that buffer descriptors are aligned in accordance to GMAC
data bus width (32/64/128-bit). It's safe to align to 128-bit (16-bytes)
for every bus width type.

If buffer descriptor is improperly aligned GMAC discards lower bits of
provided address and as a result reads from improper location that
doesn't match expected fields.

Commit ef76025a99247cdb8f927a2c9f15400678dfb599 "net: Multiple
updates/enhancements to designware.c" introduced another structure
member "link_printed" right before buffer descriptors while "padding"
member was left untouched. This together with alignment of structure
itself to 16-byte boundary forces buffer descriptoprs always to be
4-byte aligned that causes driver complete disfunction if GMAC bus width
is 64 or 128-bit.

Proposed change makes sure all buffer descriptors are 16-byte (128-bit)
aligned.

Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com>

Compared to V1 "dw_eth_dev" structure was left aligned, because I
realized that it's address will be used as a base for all the members.
And only this way I may be sure arrays of buffer descriptors are
properly aligned.
---
 drivers/net/designware.h | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/designware.h b/drivers/net/designware.h
index d668f8f..137acb0 100644
--- a/drivers/net/designware.h
+++ b/drivers/net/designware.h
@@ -128,7 +128,7 @@ struct dmamacdescr {
 	u32 dmamac_cntl;
 	void *dmamac_addr;
 	struct dmamacdescr *dmamac_next;
-};
+} __aligned(16);
 
 /*
  * txrx_status definitions
@@ -240,8 +240,7 @@ struct dw_eth_dev {
 	u32 tx_currdescnum;
 	u32 rx_currdescnum;
 	u32 phy_configured;
-	int link_printed;
-	u32 padding;
+	u32 link_printed;
 
 	struct dmamacdescr tx_mac_descrtable[CONFIG_TX_DESCR_NUM];
 	struct dmamacdescr rx_mac_descrtable[CONFIG_RX_DESCR_NUM];
@@ -253,7 +252,7 @@ struct dw_eth_dev {
 	struct eth_dma_regs *dma_regs_p;
 
 	struct eth_device *dev;
-} __attribute__ ((aligned(8)));
+};
 
 /* Speed specific definitions */
 #define SPEED_10M		1
-- 
1.8.1.2