[v2] ethtool: igb: dump RR2DCDELAY register
diff mbox series

Message ID 20190715105933.40924-1-dedekind1@gmail.com
State Accepted
Delegated to: John Linville
Headers show
Series
  • [v2] ethtool: igb: dump RR2DCDELAY register
Related show

Commit Message

Artem Bityutskiy July 15, 2019, 10:59 a.m. UTC
From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

Decode 'RR2DCDELAY' register which Linux kernel provides starting from version
5.3. The corresponding commit in the Linux kernel is:
    cd502a7f7c9c igb: add RR2DCDELAY to ethtool registers dump

The RR2DCDELAY register is present in I210 and I211 Intel Gigabit Ethernet
chips and it stands for "Read Request To Data Completion Delay". Here is how
this register is described in the I210 datasheet:

"This field captures the maximum PCIe split time in 16 ns units, which is the
maximum delay between the read request to the first data completion. This is
giving an estimation of the PCIe round trip time."

In practice, this register can be used to measure the time it takes the NIC to
read data from the host memory.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
---
 igb.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Changelog:
v2: Fixed a typo in the commentary.
v1: Initial pach version.

Comments

Michal Kubecek July 15, 2019, 7:26 p.m. UTC | #1
On Mon, Jul 15, 2019 at 01:59:33PM +0300, Artem Bityutskiy wrote:
> From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
> 
> Decode 'RR2DCDELAY' register which Linux kernel provides starting from version
> 5.3. The corresponding commit in the Linux kernel is:
>     cd502a7f7c9c igb: add RR2DCDELAY to ethtool registers dump
> 
> The RR2DCDELAY register is present in I210 and I211 Intel Gigabit Ethernet
> chips and it stands for "Read Request To Data Completion Delay". Here is how
> this register is described in the I210 datasheet:
> 
> "This field captures the maximum PCIe split time in 16 ns units, which is the
> maximum delay between the read request to the first data completion. This is
> giving an estimation of the PCIe round trip time."
> 
> In practice, this register can be used to measure the time it takes the NIC to
> read data from the host memory.
> 
> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
> ---
>  igb.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> Changelog:
> v2: Fixed a typo in the commentary.
> v1: Initial pach version.
> 
> 
> diff --git a/igb.c b/igb.c
> index e0ccef9..cb24877 100644
> --- a/igb.c
> +++ b/igb.c
> @@ -859,6 +859,18 @@ igb_dump_regs(struct ethtool_drvinfo *info, struct ethtool_regs *regs)
>  		"0x03430: TDFPC       (Tx data FIFO packet count)      0x%08X\n",
>  		regs_buff[550]);
>  
> +	/*
> +	 * Starting from kernel version 5.3 the registers dump buffer grew from
> +	 * 739 4-byte words to 740 words, and word 740 contains the RR2DCDELAY
> +	 * register.
> +	 */
> +	if (regs->len < 740)
> +		return 0;
> +
> +	fprintf(stdout,
> +		"0x05BF4: RR2DCDELAY  (Max. DMA read delay)            0x%08X\n",
> +		regs_buff[739]);
> +
>  	return 0;
>  }
>  

Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
John W. Linville July 26, 2019, 3:26 p.m. UTC | #2
On Mon, Jul 15, 2019 at 01:59:33PM +0300, Artem Bityutskiy wrote:
> From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
> 
> Decode 'RR2DCDELAY' register which Linux kernel provides starting from version
> 5.3. The corresponding commit in the Linux kernel is:
>     cd502a7f7c9c igb: add RR2DCDELAY to ethtool registers dump
> 
> The RR2DCDELAY register is present in I210 and I211 Intel Gigabit Ethernet
> chips and it stands for "Read Request To Data Completion Delay". Here is how
> this register is described in the I210 datasheet:
> 
> "This field captures the maximum PCIe split time in 16 ns units, which is the
> maximum delay between the read request to the first data completion. This is
> giving an estimation of the PCIe round trip time."
> 
> In practice, this register can be used to measure the time it takes the NIC to
> read data from the host memory.
> 
> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

Queued for next release -- thanks!

John

Patch
diff mbox series

diff --git a/igb.c b/igb.c
index e0ccef9..cb24877 100644
--- a/igb.c
+++ b/igb.c
@@ -859,6 +859,18 @@  igb_dump_regs(struct ethtool_drvinfo *info, struct ethtool_regs *regs)
 		"0x03430: TDFPC       (Tx data FIFO packet count)      0x%08X\n",
 		regs_buff[550]);
 
+	/*
+	 * Starting from kernel version 5.3 the registers dump buffer grew from
+	 * 739 4-byte words to 740 words, and word 740 contains the RR2DCDELAY
+	 * register.
+	 */
+	if (regs->len < 740)
+		return 0;
+
+	fprintf(stdout,
+		"0x05BF4: RR2DCDELAY  (Max. DMA read delay)            0x%08X\n",
+		regs_buff[739]);
+
 	return 0;
 }