Re: [PATCH net-next 3/3] net: xilinx: axienet: Add statistics support

Sean Anderson
2024-06-14T20:54:18Z

On 6/14/24 12:30, Simon Horman wrote:
> On Mon, Jun 10, 2024 at 07:10:22PM -0400, Sean Anderson wrote:
>> Add support for reading the statistics counters, if they are enabled.
>> The counters may be 64-bit, but we can't detect this as there's no
>> ability bit for it and the counters are read-only. Therefore, we assume
>> the counters are 32-bits. To ensure we don't miss an overflow, we need
>> to read all counters at regular intervals, configurable with
>> stats-block-usecs. This should be often enough to ensure the bytes
>> counters don't wrap at 2.5 Gbit/s.
>>
>> Another complication is that the counters may be reset when the device
>> is reset (depending on configuration). To ensure the counters persist
>> across link up/down (including suspend/resume), we maintain our own
>> 64-bit versions along with the last counter value we saw. Because we
>> might wait up to 100 ms for the reset to complete, we use a mutex to
>> protect writing hw_stats. We can't sleep in ndo_get_stats64, so we use a
>> u64_stats_sync to protect readers.
>>
>> We can't use the byte counters for either get_stats64 or
>> get_eth_mac_stats. This is because the byte counters include everything
>> in the frame (destination address to FCS, inclusive). But
>> rtnl_link_stats64 wants bytes excluding the FCS, and
>> ethtool_eth_mac_stats wants to exclude the L2 overhead (addresses and
>> length/type).
>>
>> Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
>> ---
>>
>> drivers/net/ethernet/xilinx/xilinx_axienet.h | 81 ++++++
>> .../net/ethernet/xilinx/xilinx_axienet_main.c | 267 +++++++++++++++++-
>> 2 files changed, 345 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet.h b/drivers/net/ethernet/xilinx/xilinx_axienet.h
>
> ...
>
>> @@ -434,6 +502,11 @@ struct skbuf_dma_descriptor {
>> * @tx_packets: TX packet count for statistics
>> * @tx_bytes: TX byte count for statistics
>> * @tx_stat_sync: Synchronization object for TX stats
>> + * @hw_last_counter: Last-seen value of each statistic
>> + * @hw_stats: Interface statistics periodically updated from hardware counters
>> + * @hw_stats_sync: Synchronization object for @hw_stats
>
> nit: s/hw_stats_sync/hw_stat_sync/
>
> Flagged by kernel-doc -none

I think I will rename the member instead.

--Sean

>> + * @stats_lock: Lock for writing @hw_stats and @hw_last_counter
>> + * @stats_work: Work for reading the hardware statistics counters
>> * @dma_err_task: Work structure to process Axi DMA errors
>> * @tx_irq: Axidma TX IRQ number
>> * @rx_irq: Axidma RX IRQ number
>> @@ -452,6 +525,7 @@ struct skbuf_dma_descriptor {
>> * @coalesce_usec_rx: IRQ coalesce delay for RX
>> * @coalesce_count_tx: Store the irq coalesce on TX side.
>> * @coalesce_usec_tx: IRQ coalesce delay for TX
>> + * @coalesce_usec_stats: Delay between hardware statistics refreshes
>> * @use_dmaengine: flag to check dmaengine framework usage.
>> * @tx_chan: TX DMA channel.
>> * @rx_chan: RX DMA channel.
>> @@ -505,6 +579,12 @@ struct axienet_local {
>> u64_stats_t tx_bytes;
>> struct u64_stats_sync tx_stat_sync;
>>
>> + u32 hw_last_counter[STAT_COUNT];
>> + u64_stats_t hw_stats[STAT_COUNT];
>> + struct u64_stats_sync hw_stat_sync;
>> + struct mutex stats_lock;
>> + struct delayed_work stats_work;
>> +
>> struct work_struct dma_err_task;
>>
>> int tx_irq;
>
> ...