ath5k: fix requested allocated RX skb size for DMA
PATCH 1/1 ath5k: fix requested allocated RX skb size for DMA
When we dev_alloc_skb() our RX buffers we were asking for them to be of size:
sc->rxbufsize + sc->common.cachelsz - 1
but when mapping processor virtual memeory for access by the hardware we were only giving it the sc->rxbufsize, therefore always preventing the device from accessing the fully allocated skb.
This patch fixes the disparity. It is unclear to me if there are other consequences to having this mismatch other than perhaps never allowing the device to use the full capacity of the allocated skb.
--- drivers/net/wireless/ath/ath5k/base.c | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-)
drivers/net/wireless/ath/ath5k/base.c +5 -3
@@ -1157,17 +1157,18 @@ struct sk_buff *ath5k_rx_skb_alloc(struct ath5k_softc *sc, dma_addr_t *skb_addr)* fake physical layer header at the start. */ skb =ath_rxbuf_alloc (&sc->common, - sc->rxbufsize + sc->common.cachelsz -1 , + sc->rxbufsize,GFP_ATOMIC );if (!skb) {ATH5K_ERR (sc,"can't alloc skbuff of size %u\n" , - sc->rxbufsize + sc->common.cachelsz -1 ); + sc->rxbufsize);return NULL ; } *skb_addr =pci_map_single (sc->pdev, skb->data, sc->rxbufsize,PCI_DMA_FROMDEVICE ); +if (unlikely (pci_dma_mapping_error (sc->pdev, *skb_addr))) {ATH5K_ERR (sc,"%s: DMA mapping failed\n" , __func__);dev_kfree_skb (skb);
@@ -1607,9 +1608,10 @@ ath5k_rx_start(struct ath5k_softc *sc)int ret; sc->rxbufsize =roundup (IEEE80211_MAX_LEN , sc->common.cachelsz); + sc->rxbufsize += sc->common.cachelsz -1 ;ATH5K_DBG (sc,ATH5K_DEBUG_RESET ,"cachelsz %u rxbufsize %u\n" , - sc->common.cachelsz, sc->rxbufsize); + sc->common.cachelsz, sc->rxbufsize);spin_lock_bh (&sc->rxbuflock); sc->rxlink =NULL ;
Signature · 1 line
1.6.3.3
PATCH 1/1 ath5k: fix requested allocated RX skb size for DMA
drivers/net/wireless/ath/ath5k/base.c struct sk_buff *ath5k_rx_skb_alloc(struct ath5k_softc *sc, dma_addr_t *skb_addr) · line 1160
Quoted 7 lines · Luis R. Rodriguez
drivers/net/wireless/ath/ath5k/base.c +0
-1@@ -1157,17 +1157,18 @@ struct sk_buff *ath5k_rx_skb_alloc(struct ath5k_softc *sc, dma_addr_t *skb_addr)* fake physical layer header at the start. */ skb = ath_rxbuf_alloc(&sc->common, - sc->rxbufsize + sc->common.cachelsz - 1,
What was the exact purpose of this? My guess is that we should map starting at a next cache line boundary and put this aligned address to the device instead?
PATCH 1/1 ath5k: fix requested allocated RX skb size for DMA
Quoted 12 lines · Jiri Slaby
Quoted 7 lines · Luis R. Rodriguez
drivers/net/wireless/ath/ath5k/base.c +0
-0@@ -1157,17 +1157,18 @@ struct sk_buff *ath5k_rx_skb_alloc(struct ath5k_softc *sc, dma_addr_t *skb_addr)? ? ? ?* fake physical layer header at the start.
? ? ? ?*/
? ? ? skb = ath_rxbuf_alloc(&sc->common,
- ? ? ? ? ? ? ? ? ? ? ? ? ?sc->rxbufsize+sc->common.cachelsz- 1,What was the exact purpose of this? My guess is that we should map starting at a next cache line boundary and put this aligned address to the device instead?
I've heard two theories:
1) AR5210 *required* it otherwise bad we would get bad data
2) Performance considerations
I've tried checking internally but haven't found out yet the exact answer and this seems purely historical. I poked Sam Leffler to see if he recalls. But as we the 0x41 reset which I removed it seems to be best to leave unless we can be 100% sure we can remove this.
Luis
PATCH 1/1 ath5k: fix requested allocated RX skb size for DMA
Quoted 9 lines · Luis R. Rodriguez
Quoted 3 lines · Jiri Slaby
What was the exact purpose of this? My guess is that we should map starting at a next cache line boundary and put this aligned address to the device instead?
I've heard two theories:
1) AR5210 *required* it otherwise bad we would get bad data
2) Performance considerations
PATCH 1/1 ath5k: fix requested allocated RX skb size for DMA
John please ignore this patch, its busted, as Bob noted on IRC.
Luis