Commit 2d7c7939 authored by Ben Hutchings's avatar Ben Hutchings Committed by David S. Miller
Browse files

ethtool: Correct description of 'max_coalesced_frames' fields 



The current descriptions state that these fields specify 'How many
packets to delay ... after a packet ...' which implies that the
hardware should wait for (max_coalesced_frames + 1) completions before
generating an interrupt.  It is also stated that setting both this
field and the corresponding 'coalesce_usecs' field to 0 is invalid.
Together, this implies that the hardware must always be configured
to delay a completion IRQ for at least 1 usec or 1 more completion.

I believe that the addition of 1 is not intended, and David Miller
confirms that the original implementation (in tg3) does not do this.
Clarify the descriptions of these fields to avoid this interpretation.

Signed-off-by: default avatarBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 725b361b

include/linux/ethtool.h

+13 −13
Original line number Diff line number Diff line
@@ -122,8 +122,8 @@ struct ethtool_eeprom { 
 * @cmd: ETHTOOL_{G,S}COALESCE

 * @rx_coalesce_usecs: How many usecs to delay an RX interrupt after

 *	a packet arrives.  If 0, only @rx_max_coalesced_frames is used.

 * @rx_max_coalesced_frames: How many packets to delay an RX interrupt

 *	after a packet arrives.  If 0, only @rx_coalesce_usecs is used.

 * @rx_max_coalesced_frames: Maximum number of packets to receive

 *	before an RX interrupt.  If 0, only @rx_coalesce_usecs is used.

 * @rx_coalesce_usecs_irq: Same as @rx_coalesce_usecs, except that

 *	this value applies while an IRQ is being serviced by the host.

 * @rx_max_coalesced_frames_irq: Same as @rx_max_coalesced_frames,
@@ -132,8 +132,8 @@ struct ethtool_eeprom { 
 * @tx_coalesce_usecs: How many usecs to delay a TX interrupt after

 *	a packet is sent.  If 0, only @tx_max_coalesced_frames

 *	is used.

 * @tx_max_coalesced_frames: How many packets to delay a TX interrupt

 *	after a packet is sent.  If 0, only @tx_coalesce_usecs is

 * @tx_max_coalesced_frames: Maximum number of packets to be sent

 *	before a TX interrupt.  If 0, only @tx_coalesce_usecs is

 *     used.

 * @tx_coalesce_usecs_irq: Same as @tx_coalesce_usecs, except that

 *	this value applies while an IRQ is being serviced by the host.
@@ -149,21 +149,21 @@ struct ethtool_eeprom { 
 * @pkt_rate_low: Threshold for low packet rate (packets per second).

 * @rx_coalesce_usecs_low: How many usecs to delay an RX interrupt after

 *	a packet arrives, when the packet rate is below @pkt_rate_low.

 * @rx_max_coalesced_frames_low: How many packets to delay an RX interrupt

 *	after a packet arrives, when the packet rate is below @pkt_rate_low.

 * @rx_max_coalesced_frames_low: Maximum number of packets to be received

 *	before an RX interrupt, when the packet rate is below @pkt_rate_low.

 * @tx_coalesce_usecs_low: How many usecs to delay a TX interrupt after

 *	a packet is sent, when the packet rate is below @pkt_rate_low.

 * @tx_max_coalesced_frames_low: How many packets to delay a TX interrupt

 *	after a packet is sent, when the packet rate is below @pkt_rate_low.

 * @tx_max_coalesced_frames_low: Maximum nuumber of packets to be sent before

 *	a TX interrupt, when the packet rate is below @pkt_rate_low.

 * @pkt_rate_high: Threshold for high packet rate (packets per second).

 * @rx_coalesce_usecs_high: How many usecs to delay an RX interrupt after

 *	a packet arrives, when the packet rate is above @pkt_rate_high.

 * @rx_max_coalesced_frames_high: How many packets to delay an RX interrupt

 *	after a packet arrives, when the packet rate is above @pkt_rate_high.

 * @rx_max_coalesced_frames_high: Maximum number of packets to be received

 *	before an RX interrupt, when the packet rate is above @pkt_rate_high.

 * @tx_coalesce_usecs_high: How many usecs to delay a TX interrupt after

 *	a packet is sent, when the packet rate is above @pkt_rate_high.

 * @tx_max_coalesced_frames_high: How many packets to delay a TX interrupt

 *	after a packet is sent, when the packet rate is above @pkt_rate_high.

 * @tx_max_coalesced_frames_high: Maximum number of packets to be sent before

 *	a TX interrupt, when the packet rate is above @pkt_rate_high.

 * @rate_sample_interval: How often to do adaptive coalescing packet rate

 *	sampling, measured in seconds.  Must not be zero.

 *

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