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Re: [PATCH] Netpoll support for Sibyte MAC

To: dsaxena@plexity.net
Subject: Re: [PATCH] Netpoll support for Sibyte MAC
From: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Date: Tue, 20 Mar 2007 17:34:01 +0300
Cc: netdev@vger.kernel.org, ralf@linux-mips.org, jeff@garzik.org, linux-mips@linux-mips.org, Manish Lachwani <mlachwani@mvista.com>
In-reply-to: <20070319224311.GA10176@plexity.net>
Organization: MontaVista Software Inc.
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20070319224311.GA10176@plexity.net>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mozilla/5.0 (X11; U; Linux i686; rv:1.7.2) Gecko/20040803
Hello.

Deepak Saxena wrote:

NETPOLL support for Sibyte MAC

Index: linux-2.6.18/drivers/net/sb1250-mac.c
===================================================================
--- linux-2.6.18.orig/drivers/net/sb1250-mac.c
+++ linux-2.6.18/drivers/net/sb1250-mac.c
@@ -1128,6 +1128,26 @@ static void sbdma_fillring(sbmacdma_t *d
        }
 }
+#ifdef CONFIG_NET_POLL_CONTROLLER
+static void sbmac_netpoll(struct net_device *netdev)
+{
+       struct sbmac_softc *sc = netdev_priv(netdev);
+       int irq = sc->sbm_dev->irq;
+
+       __raw_writeq(0, sc->sbm_imr);
+

Thinking about it again, I'm not sure that blindly writing to the chip reg. to mask interrupts is SMP-safe enough (versus disable_irq()). I know why it was done this way -- to quell the BUG emitted in the realtime mode on SMP -- because of scheduling with disabled interrupts in synchoronize_irq(), but after having spent much time on netpoll, I'm no longer sure that anything but disable_irq() is safe enough for SMP since -- otherwise there's no warranty that sbmac_intr() is not running on another CPU...

+       sbmac_intr(irq, netdev, NULL);
+
+#ifdef CONFIG_SBMAC_COALESCE
+       __raw_writeq(((M_MAC_INT_EOP_COUNT | M_MAC_INT_EOP_TIMER) << 
S_MAC_TX_CH0) |
+       ((M_MAC_INT_EOP_COUNT | M_MAC_INT_EOP_TIMER) << S_MAC_RX_CH0),
+       sc->sbm_imr);
+#else
+ __raw_writeq((M_MAC_INT_CHANNEL << S_MAC_TX_CH0) | + (M_MAC_INT_CHANNEL << S_MAC_RX_CH0), sc->sbm_imr);
+#endif
+}
+#endif

WBR, Sergei

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