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authorFlorian Fainelli <f.fainelli@gmail.com>2018-03-14 00:45:07 +0300
committerDavid S. Miller <davem@davemloft.net>2018-03-16 18:16:55 +0300
commit484d802d0f2f29c335563fcac2a8facf174a1bbc (patch)
treeb1a971b0b45f5a99c1ebd93a15fea0ad0d00600d /drivers/net/ethernet/broadcom/bcmsysport.h
parent2cc683e88c0c993ac3721d9b702cb0630abe2879 (diff)
downloadlinux-484d802d0f2f29c335563fcac2a8facf174a1bbc.tar.xz
net: systemport: Rewrite __bcm_sysport_tx_reclaim()
There is no need for complex checking between the last consumed index and current consumed index, a simple subtraction will do. This also eliminates the possibility of a permanent transmit queue stall under the following conditions: - one CPU bursts ring->size worth of traffic (up to 256 buffers), to the point where we run out of free descriptors, so we stop the transmit queue at the end of bcm_sysport_xmit() - because of our locking, we have the transmit process disable interrupts which means we can be blocking the TX reclamation process - when TX reclamation finally runs, we will be computing the difference between ring->c_index (last consumed index by SW) and what the HW reports through its register - this register is masked with (ring->size - 1) = 0xff, which will lead to stripping the upper bits of the index (register is 16-bits wide) - we will be computing last_tx_cn as 0, which means there is no work to be done, and we never wake-up the transmit queue, leaving it permanently disabled A practical example is e.g: ring->c_index aka last_c_index = 12, we pushed 256 entries, HW consumer index = 268, we mask it with 0xff = 12, so last_tx_cn == 0, nothing happens. Fixes: 80105befdb4b ("net: systemport: add Broadcom SYSTEMPORT Ethernet MAC driver") Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ethernet/broadcom/bcmsysport.h')
-rw-r--r--drivers/net/ethernet/broadcom/bcmsysport.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/net/ethernet/broadcom/bcmsysport.h b/drivers/net/ethernet/broadcom/bcmsysport.h
index f5a984c1c986..19c91c76e327 100644
--- a/drivers/net/ethernet/broadcom/bcmsysport.h
+++ b/drivers/net/ethernet/broadcom/bcmsysport.h
@@ -706,7 +706,7 @@ struct bcm_sysport_tx_ring {
unsigned int desc_count; /* Number of descriptors */
unsigned int curr_desc; /* Current descriptor */
unsigned int c_index; /* Last consumer index */
- unsigned int p_index; /* Current producer index */
+ unsigned int clean_index; /* Current clean index */
struct bcm_sysport_cb *cbs; /* Transmit control blocks */
struct dma_desc *desc_cpu; /* CPU view of the descriptor */
struct bcm_sysport_priv *priv; /* private context backpointer */