From: Thierry Reding treding@nvidia.com
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 ---
Changes in v3: - Remove cache-line size warning if dcache is disabled
drivers/net/rtl8169.c | 71 +++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 60 insertions(+), 11 deletions(-)
diff --git a/drivers/net/rtl8169.c b/drivers/net/rtl8169.c index fc8c31e..cd26c36 100644 --- a/drivers/net/rtl8169.c +++ b/drivers/net/rtl8169.c @@ -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 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 @@ -418,34 +418,71 @@ match: }
/* + * 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. */
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++; }