netdev - [PATCH 1/2] sfc: Remove requirement to set tx-usecs-irq for shared channels when modifying coalescing parameters

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Date:	Wed, 31 Aug 2011 10:52:36 +0100
From:	Ripduman Sohan <ripduman.sohan@...cam.ac.uk>
To:	linux-net-drivers@...arflare.com, shodgson@...arflare.com,
	bhutchings@...arflare.com
Cc:	netdev@...r.kernel.org,
	Ripduman Sohan <ripduman.sohan@...cam.ac.uk>
Subject: [PATCH 1/2] sfc: Remove requirement to set tx-usecs-irq for shared channels when modifying coalescing parameters

Shared TX/RX channels possess a single channel timer controlled by the
rx-usecs-irq parameter.  Changing coalescing parameters required
explicitly setting the tx-usecs-irq parameter to 0.  Ethtool (to HEAD
of tree) does not do this and instead retrieves and re-submits the
current tx-usecs-irq value resulting in an unsupported operation
error.  I found this behaviour counter-intuitive and was only able to
work out correct moderation parameters by studying the driver code.

This patch relaxes the requirement to set tx-usecs-irq to 0 by only
erring if the presented tx-usecs-irq value differs from the current
value.  I acknowledge, however, that there may be existing scripts
relying on the old behaviour and so this condition is only triggered
if a value for tx-usecs-irq is actually presented.
---
 drivers/net/sfc/efx.c     |    6 +++---
 drivers/net/sfc/efx.h     |    1 +
 drivers/net/sfc/ethtool.c |    4 +++-
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index faca764..9a313cd 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -1556,7 +1556,7 @@ static void efx_remove_all(struct efx_nic *efx)
  *
  **************************************************************************/
 
-static unsigned irq_mod_ticks(int usecs, int resolution)
+unsigned efx_irq_mod_ticks(int usecs, int resolution)
 {
 	if (usecs <= 0)
 		return 0; /* cannot receive interrupts ahead of time :-) */
@@ -1570,8 +1570,8 @@ void efx_init_irq_moderation(struct efx_nic *efx, int tx_usecs, int rx_usecs,
 			     bool rx_adaptive)
 {
 	struct efx_channel *channel;
-	unsigned tx_ticks = irq_mod_ticks(tx_usecs, EFX_IRQ_MOD_RESOLUTION);
-	unsigned rx_ticks = irq_mod_ticks(rx_usecs, EFX_IRQ_MOD_RESOLUTION);
+	unsigned tx_ticks = efx_irq_mod_ticks(tx_usecs, EFX_IRQ_MOD_RESOLUTION);
+	unsigned rx_ticks = efx_irq_mod_ticks(rx_usecs, EFX_IRQ_MOD_RESOLUTION);
 
 	EFX_ASSERT_RESET_SERIALISED(efx);
 
diff --git a/drivers/net/sfc/efx.h b/drivers/net/sfc/efx.h
index b0d1209..ddfcc7e 100644
--- a/drivers/net/sfc/efx.h
+++ b/drivers/net/sfc/efx.h
@@ -113,6 +113,7 @@ extern int efx_reset_up(struct efx_nic *efx, enum reset_type method, bool ok);
 extern void efx_schedule_reset(struct efx_nic *efx, enum reset_type type);
 extern void efx_init_irq_moderation(struct efx_nic *efx, int tx_usecs,
 				    int rx_usecs, bool rx_adaptive);
+extern unsigned efx_irq_mod_ticks(int usecs, int resolution);
 
 /* Dummy PHY ops for PHY drivers */
 extern int efx_port_dummy_op_int(struct efx_nic *efx);
diff --git a/drivers/net/sfc/ethtool.c b/drivers/net/sfc/ethtool.c
index bc4643a..0a52447 100644
--- a/drivers/net/sfc/ethtool.c
+++ b/drivers/net/sfc/ethtool.c
@@ -644,7 +644,9 @@ static int efx_ethtool_set_coalesce(struct net_device *net_dev,
 	efx_for_each_channel(channel, efx) {
 		if (efx_channel_has_rx_queue(channel) &&
 		    efx_channel_has_tx_queues(channel) &&
-		    tx_usecs) {
+		    tx_usecs &&
+		    efx_irq_mod_ticks(tx_usecs, EFX_IRQ_MOD_RESOLUTION) !=
+		    channel->irq_moderation) {
 			netif_err(efx, drv, efx->net_dev, "Channel is shared. "
 				  "Only RX coalescing may be set\n");
 			return -EOPNOTSUPP;
-- 
1.7.1

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