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net: rtl8169: Use non-cached memory if available

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To work around potential issues with explicit cache maintenance of the
RX and TX descriptor rings, allocate them from a pool of uncached memory
if the architecture supports it.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>
This commit is contained in:
Thierry Reding 2014-12-09 22:25:26 -07:00 committed by Tom Warren
parent dad3ba0f0b
commit d58acdcbfb
1 changed files with 60 additions and 11 deletions
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71
drivers/net/rtl8169.c
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@ -41,6 +41,7 @@
* Modified to use le32_to_cpu and cpu_to_le32 properly
*/
#include <common.h>
#include <errno.h>
#include <malloc.h>
#include <net.h>
#include <netdev.h>
@ -290,16 +291,15 @@ struct RxDesc {
* cases the driver will likely fail because the CPU needs to flush the cache
* when requeuing RX buffers, therefore descriptors written by the hardware
* may be discarded.
*
* This can be fixed by defining CONFIG_SYS_NONCACHED_MEMORY which will cause
* the driver to allocate descriptors from a pool of non-cached memory.
*/
#if RTL8169_DESC_SIZE < ARCH_DMA_MINALIGN
#if !defined(CONFIG_SYS_NONCACHED_MEMORY) && !defined(CONFIG_SYS_DCACHE_OFF)
#warning cache-line size is larger than descriptor size
#endif
/* Define the TX Descriptor */
DEFINE_ALIGN_BUFFER(struct TxDesc, tx_ring, NUM_TX_DESC, RTL8169_ALIGN);
/* Define the RX Descriptor */
DEFINE_ALIGN_BUFFER(struct RxDesc, rx_ring, NUM_RX_DESC, RTL8169_ALIGN);
#endif
/*
* Create a static buffer of size RX_BUF_SZ for each TX Descriptor. All
@ -417,6 +417,35 @@ match:
return 0;
}
/*
* TX and RX descriptors are 16 bytes. This causes problems with the cache
* maintenance on CPUs where the cache-line size exceeds the size of these
* descriptors. What will happen is that when the driver receives a packet
* it will be immediately requeued for the hardware to reuse. The CPU will
* therefore need to flush the cache-line containing the descriptor, which
* will cause all other descriptors in the same cache-line to be flushed
* along with it. If one of those descriptors had been written to by the
* device those changes (and the associated packet) will be lost.
*
* To work around this, we make use of non-cached memory if available. If
* descriptors are mapped uncached there's no need to manually flush them
* or invalidate them.
*
* Note that this only applies to descriptors. The packet data buffers do
* not have the same constraints since they are 1536 bytes large, so they
* are unlikely to share cache-lines.
*/
static void *rtl_alloc_descs(unsigned int num)
{
size_t size = num * RTL8169_DESC_SIZE;
#ifdef CONFIG_SYS_NONCACHED_MEMORY
return (void *)noncached_alloc(size, RTL8169_ALIGN);
#else
return memalign(RTL8169_ALIGN, size);
#endif
}
/*
* Cache maintenance functions. These are simple wrappers around the more
* general purpose flush_cache() and invalidate_dcache_range() functions.
@ -424,28 +453,36 @@ match:
static void rtl_inval_rx_desc(struct RxDesc *desc)
{
#ifndef CONFIG_SYS_NONCACHED_MEMORY
unsigned long start = (unsigned long)desc & ~(ARCH_DMA_MINALIGN - 1);
unsigned long end = ALIGN(start + sizeof(*desc), ARCH_DMA_MINALIGN);
invalidate_dcache_range(start, end);
#endif
}
static void rtl_flush_rx_desc(struct RxDesc *desc)
{
#ifndef CONFIG_SYS_NONCACHED_MEMORY
flush_cache((unsigned long)desc, sizeof(*desc));
#endif
}
static void rtl_inval_tx_desc(struct TxDesc *desc)
{
#ifndef CONFIG_SYS_NONCACHED_MEMORY
unsigned long start = (unsigned long)desc & ~(ARCH_DMA_MINALIGN - 1);
unsigned long end = ALIGN(start + sizeof(*desc), ARCH_DMA_MINALIGN);
invalidate_dcache_range(start, end);
#endif
}
static void rtl_flush_tx_desc(struct TxDesc *desc)
{
#ifndef CONFIG_SYS_NONCACHED_MEMORY
flush_cache((unsigned long)desc, sizeof(*desc));
#endif
}
static void rtl_inval_buffer(void *buf, size_t size)
@ -912,10 +949,16 @@ static int rtl_init(struct eth_device *dev, bd_t *bis)
#endif
}
tpc->TxDescArray = tx_ring;
tpc->RxDescArray = rx_ring;
return 1;
tpc->RxDescArray = rtl_alloc_descs(NUM_RX_DESC);
if (!tpc->RxDescArray)
return -ENOMEM;
tpc->TxDescArray = rtl_alloc_descs(NUM_TX_DESC);
if (!tpc->TxDescArray)
return -ENOMEM;
return 0;
}
int rtl8169_initialize(bd_t *bis)
@ -929,6 +972,7 @@ int rtl8169_initialize(bd_t *bis)
while(1){
unsigned int region;
u16 device;
int err;
/* Find RTL8169 */
if ((devno = pci_find_devices(supported, idx++)) < 0)
@ -967,9 +1011,14 @@ int rtl8169_initialize(bd_t *bis)
dev->send = rtl_send;
dev->recv = rtl_recv;
eth_register (dev);
err = rtl_init(dev, bis);
if (err < 0) {
printf(pr_fmt("failed to initialize card: %d\n"), err);
free(dev);
continue;
}
rtl_init(dev, bis);
eth_register (dev);
card_number++;
}