net/designware: reorder struct dw_eth_dev to pack more efficiently.

On Thu, 2014-05-08 at 22:26 +0100, Ian Campbell wrote:
> The {r,t}xbuffs fields also need to be aligned. Previously this was done
> implicitly because they immediately followed the descriptor tables. Make this
> explicit and also move to the head of the struct.

Looks like I managed to not actually commit the move of the field to the
head of the struct! v3.1 follows....

Ian.

8<------------

>From 2937ba01841887317f6792709ed57cb86b5fc0cd Mon Sep 17 00:00:00 2001
From: Ian Campbell <ijc@hellion.org.uk>
Date: Thu, 1 May 2014 19:45:15 +0100
Subject: [PATCH] net/designware: reorder struct dw_eth_dev to pack more
 efficiently.

The {tx,rx}_mac_descrtable fields are aligned to ARCH_DMA_MINALIGN, which could
be 256 or even larger. That means there is a potentially huge hole in the
struct before those fields, so move them to the front where they are better
packed.

Moving them to the front also helps ensure that so long as dw_eth_dev is
properly aligned (which it is since "net/designware: ensure device private data
is DMA aligned.") the {tx,rx}_mac_descrtable will be too, or at least avoids
having to worry too much about compiler specifics.

The {r,t}xbuffs fields also need to be aligned. Previously this was done
implicitly because they immediately followed the descriptor tables. Make this
explicit and also move to the head of the struct.

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Tested-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Reviewed-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>

diff --git a/drivers/net/designware.h b/drivers/net/designware.h
index 382b0c7f0a66c2a9dd4dab562a13f16f780e2bda..de2fdcb1f2fb77c685d816b5fc102767e8433106 100644 (file)
--- a/drivers/net/designware.h
+++ b/drivers/net/designware.h
@@ -215,15 +215,14 @@ struct dmamacdescr {
 #endif
 
 struct dw_eth_dev {
-       u32 interface;
-       u32 tx_currdescnum;
-       u32 rx_currdescnum;
-
        struct dmamacdescr tx_mac_descrtable[CONFIG_TX_DESCR_NUM];
        struct dmamacdescr rx_mac_descrtable[CONFIG_RX_DESCR_NUM];
+       char txbuffs[TX_TOTAL_BUFSIZE] __aligned(ARCH_DMA_MINALIGN);
+       char rxbuffs[RX_TOTAL_BUFSIZE] __aligned(ARCH_DMA_MINALIGN);
 
-       char txbuffs[TX_TOTAL_BUFSIZE];
-       char rxbuffs[RX_TOTAL_BUFSIZE];
+       u32 interface;
+       u32 tx_currdescnum;
+       u32 rx_currdescnum;
 
        struct eth_mac_regs *mac_regs_p;
        struct eth_dma_regs *dma_regs_p;