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Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock

From Pavel Machek <pavel@ucw.cz>
Newsgroups linux.kernel
Subject Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock
Date 2016-12-19 11:10 +0100
Message-ID <sQ33k-6mo-5@gated-at.bofh.it> (permalink)
References (5 earlier) <sOLBw-2r7-17@gated-at.bofh.it> <sOLUR-2xu-7@gated-at.bofh.it> <sOMQW-38F-19@gated-at.bofh.it> <sPr7H-4aS-1@gated-at.bofh.it> <sPxmO-8sN-7@gated-at.bofh.it>
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Hi!

> Lino, have you considered via-rhine.c since its "move work from irq to
> workqueue context" changes that started in
> 7ab87ff4c770eed71e3777936299292739fcd0fe [*] ?
> 
> It's a shameless plug - originated in r8169.c - but it should be rather
> close to what the sxgbe and friends require. Thought / opinion ?
> 
> [*] Including fixes/changes in:
> - 3a5a883a8a663b930908cae4abe5ec913b9b2fd2
> - e1efa87241272104d6a12c8b9fcdc4f62634d447
> - 810f19bcb862f8889b27e0c9d9eceac9593925dd
> - e45af497950a89459a0c4b13ffd91e1729fffef4
> - a926592f5e4e900f3fa903298c4619a131e60963
> - 559bcac35facfed49ab4f408e162971612dcfdf3

Considering the memory barriers... is something like this neccessary
in the via-rhine?

AFAICT... we need a barrier after making sure that descriptor is no
longer owned by DMA (to make sure we don't get stale data in rest of
descriptor)... and we need a barrier before giving the descriptor to
the dma, to make sure DMA engine sees the complete update....?

Thanks,
								Pavel

diff --git a/drivers/net/ethernet/via/via-rhine.c b/drivers/net/ethernet/via/via-rhine.c
index ba5c542..3806e72 100644
--- a/drivers/net/ethernet/via/via-rhine.c
+++ b/drivers/net/ethernet/via/via-rhine.c
@@ -1952,6 +1952,7 @@ static void rhine_tx(struct net_device *dev)
 			  entry, txstatus);
 		if (txstatus & DescOwn)
 			break;
+		dma_rmb();
 		skb = rp->tx_skbuff[entry];
 		if (txstatus & 0x8000) {
 			netif_dbg(rp, tx_done, dev,
@@ -2061,6 +2062,7 @@ static int rhine_rx(struct net_device *dev, int limit)
 
 		if (desc_status & DescOwn)
 			break;
+		dma_rmb();
 
 		netif_dbg(rp, rx_status, dev, "%s() status %08x\n", __func__,
 			  desc_status);
@@ -2146,6 +2148,7 @@ static int rhine_rx(struct net_device *dev, int limit)
 			u64_stats_update_end(&rp->rx_stats.syncp);
 		}
 give_descriptor_to_nic:
+		dma_wmb();
 		desc->rx_status = cpu_to_le32(DescOwn);
 		entry = (++rp->cur_rx) % RX_RING_SIZE;
 	}

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Pavel Machek <pavel@ucw.cz> - 2016-12-11 21:20 +0100
  Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Lino Sanfilippo <LinoSanfilippo@gmx.de> - 2016-12-15 20:30 +0100
    Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Pavel Machek <pavel@ucw.cz> - 2016-12-15 22:20 +0100
      Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Lino Sanfilippo <LinoSanfilippo@gmx.de> - 2016-12-15 22:40 +0100
        Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Lino Sanfilippo <LinoSanfilippo@gmx.de> - 2016-12-15 23:40 +0100
          Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Pavel Machek <pavel@ucw.cz> - 2016-12-17 18:40 +0100
            Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Francois Romieu <romieu@fr.zoreil.com> - 2016-12-18 01:20 +0100
              Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Lino Sanfilippo <LinoSanfilippo@gmx.de> - 2016-12-18 17:20 +0100
                Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Pavel Machek <pavel@ucw.cz> - 2016-12-18 18:30 +0100
                Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Pavel Machek <pavel@ucw.cz> - 2016-12-18 19:40 +0100
                Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Lino Sanfilippo <LinoSanfilippo@gmx.de> - 2016-12-19 23:50 +0100
                Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Pavel Machek <pavel@ucw.cz> - 2016-12-18 21:20 +0100
              Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Pavel Machek <pavel@ucw.cz> - 2016-12-19 11:10 +0100
                Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Francois Romieu <romieu@fr.zoreil.com> - 2016-12-20 01:10 +0100

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