From: <Parthiban.Veerasooran@microchip.com>
To: <andrew@lunn.ch>
Cc: <davem@davemloft.net>, <edumazet@google.com>, <kuba@kernel.org>,
<pabeni@redhat.com>, <horms@kernel.org>, <saeedm@nvidia.com>,
<anthony.l.nguyen@intel.com>, <netdev@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <corbet@lwn.net>,
<linux-doc@vger.kernel.org>, <robh+dt@kernel.org>,
<krzysztof.kozlowski+dt@linaro.org>, <conor+dt@kernel.org>,
<devicetree@vger.kernel.org>, <Horatiu.Vultur@microchip.com>,
<ruanjinjie@huawei.com>, <Steen.Hegelund@microchip.com>,
<vladimir.oltean@nxp.com>, <UNGLinuxDriver@microchip.com>,
<Thorsten.Kummermehr@microchip.com>, <Pier.Beruto@onsemi.com>,
<Selvamani.Rajagopal@onsemi.com>, <Nicolas.Ferre@microchip.com>,
<benjamin.bigler@bernformulastudent.ch>
Subject: Re: [PATCH net-next v3 08/12] net: ethernet: oa_tc6: implement transmit path to transfer tx ethernet frames
Date: Tue, 19 Mar 2024 12:54:30 +0000 [thread overview]
Message-ID: <f9d8a18c-b1fe-450c-a5ca-d91f96793a04@microchip.com> (raw)
In-Reply-To: <208fb61b-4740-46bf-8c70-29ab59cbb965@lunn.ch>
Hi Andrew,
On 07/03/24 10:38 pm, Andrew Lunn wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
>> @@ -55,6 +77,14 @@
>> (OA_TC6_CTRL_MAX_REGISTERS *\
>> OA_TC6_CTRL_REG_VALUE_SIZE) +\
>> OA_TC6_CTRL_IGNORED_SIZE)
>> +#define OA_TC6_CHUNK_PAYLOAD_SIZE 64
>> +#define OA_TC6_DATA_HEADER_SIZE 4
>> +#define OA_TC6_CHUNK_SIZE (OA_TC6_DATA_HEADER_SIZE +\
>> + OA_TC6_CHUNK_PAYLOAD_SIZE)
>> +#define OA_TC6_TX_SKB_QUEUE_SIZE 100
>
> So you keep up to 100 packets in a queue. If use assume typical MTU
> size packets, that is 1,238,400 bits. At 10Mbps, that is 120ms of
> traffic. That is quite a lot of latency when a high priority packet is
> added to the tail of the queue and needs to wait for all the other
> packets to be sent first.
>
> Chunks are 64 bytes. So in practice, you only ever need two
> packets. You need to be able to fill a chunk with the final part of
> one packet, and the beginning of the next. So i would try using a much
> smaller queue size. That will allow Linux queue disciplines to give
> you the high priority packets first which you send with low latency.
Thanks for the detailed explanation. If I understand you correctly,
1. The tx skb queue size (OA_TC6_TX_SKB_QUEUE_SIZE) should be 2 to avoid
the latency when a high priority packet added.
2. Need to implement the handling part of the below case,
In case if one packet ends in a chunk and that chunk still having some
space left to accommodate some bytes from the next packet if available
from network layer.
Will implement in the next version.
>
>> +static void oa_tc6_add_tx_skb_to_spi_buf(struct oa_tc6 *tc6)
>> +{
>> + enum oa_tc6_data_start_valid_info start_valid = OA_TC6_DATA_START_INVALID;
>> + enum oa_tc6_data_end_valid_info end_valid = OA_TC6_DATA_END_INVALID;
>> + __be32 *tx_buf = tc6->spi_data_tx_buf + tc6->spi_data_tx_buf_offset;
>> + u16 remaining_length = tc6->tx_skb->len - tc6->tx_skb_offset;
>> + u8 *tx_skb_data = tc6->tx_skb->data + tc6->tx_skb_offset;
>> + u8 end_byte_offset = 0;
>> + u16 length_to_copy;
>> +
>> + /* Set start valid if the current tx chunk contains the start of the tx
>> + * ethernet frame.
>> + */
>> + if (!tc6->tx_skb_offset)
>> + start_valid = OA_TC6_DATA_START_VALID;
>> +
>> + /* If the remaining tx skb length is more than the chunk payload size of
>> + * 64 bytes then copy only 64 bytes and leave the ongoing tx skb for
>> + * next tx chunk.
>> + */
>> + length_to_copy = min_t(u16, remaining_length, OA_TC6_CHUNK_PAYLOAD_SIZE);
>> +
>> + /* Copy the tx skb data to the tx chunk payload buffer */
>> + memcpy(tx_buf + 1, tx_skb_data, length_to_copy);
>> + tc6->tx_skb_offset += length_to_copy;
>
> You probably need a call to skb_linearize() somewhere. You assume the
> packet data is contiguous. It can in fact be split into multiple
> segments. skb_linearize() will convert it to a single buffer.
Ah ok. Then probably I have to add the below code in the
oa_tc6_start_xmit() function before adding the skb into the transmit queue.
if (skb_linearize(skb)) {
dev_kfree_skb_any(skb);
tc6->netdev->stats.tx_dropped++;
return NETDEV_TX_OK;
}
>
>> +static int oa_tc6_try_spi_transfer(struct oa_tc6 *tc6)
>> +{
>> + int ret;
>> +
>> + while (true) {
>> + u16 spi_length = 0;
>> +
>> + tc6->spi_data_tx_buf_offset = 0;
>> +
>> + if (tc6->tx_skb || !skb_queue_empty(&tc6->tx_skb_q))
>> + spi_length = oa_tc6_prepare_spi_tx_buf_for_tx_skbs(tc6);
>> +
>> + if (spi_length == 0)
>> + break;
>> +
>> + ret = oa_tc6_spi_transfer(tc6, OA_TC6_DATA_HEADER, spi_length);
>> + if (ret) {
>> + netdev_err(tc6->netdev,
>> + "SPI data transfer failed. Restart the system: %d\n",
>> + ret);
>
> What does Restart the system mean?
Hmm, actually if SPI transfer failed then it can be hardware failure or
poor SPI connection. Now I realize that just restarting the system will
not help. I will remove "Restart the system:" as it is not the correct info.
>
>> +static int oa_tc6_spi_thread_handler(void *data)
>> +{
>> + struct oa_tc6 *tc6 = data;
>> + int ret;
>> +
>> + while (likely(!kthread_should_stop())) {
>> + /* This kthread will be waken up if there is a tx skb */
>> + wait_event_interruptible(tc6->spi_wq,
>> + !skb_queue_empty(&tc6->tx_skb_q) ||
>> + kthread_should_stop());
>> + ret = oa_tc6_try_spi_transfer(tc6);
>
> Shouldn't you check why you have been woken up? It seems more logical
> to test here for kthread_should_stop() rather than have
> oa_tc6_try_spi_transfer() handle there is not actually a packet to be
> sent.
Ok, then I will add the below code before the oa_tc6_try_spi_transfer().
if (kthread_should_stop())
break;
Best regards,
Parthiban V
>
> Andrew
>
next prev parent reply other threads:[~2024-03-19 12:55 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-06 8:50 [PATCH net-next v3 00/12] Add support for OPEN Alliance 10BASE-T1x MACPHY Serial Interface Parthiban Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 01/12] Documentation: networking: add OPEN Alliance 10BASE-T1x MAC-PHY serial interface Parthiban Veerasooran
2024-03-06 13:23 ` Andrew Lunn
2024-03-07 6:29 ` Parthiban.Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 02/12] net: ethernet: oa_tc6: implement register write operation Parthiban Veerasooran
2024-03-06 13:40 ` Andrew Lunn
2024-03-07 6:46 ` Parthiban.Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 03/12] net: ethernet: oa_tc6: implement register read operation Parthiban Veerasooran
2024-03-07 0:19 ` Andrew Lunn
2024-03-07 7:04 ` Parthiban.Veerasooran
2024-03-07 13:22 ` Andrew Lunn
2024-03-08 7:12 ` Parthiban.Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 04/12] net: ethernet: oa_tc6: implement software reset Parthiban Veerasooran
2024-03-07 0:35 ` Andrew Lunn
2024-03-07 7:39 ` Parthiban.Veerasooran
2024-03-07 13:24 ` Andrew Lunn
2024-03-08 8:25 ` Parthiban.Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 05/12] net: ethernet: oa_tc6: implement error interrupts unmasking Parthiban Veerasooran
2024-03-07 0:43 ` Andrew Lunn
2024-03-07 8:28 ` Parthiban.Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 06/12] net: ethernet: oa_tc6: implement internal PHY initialization Parthiban Veerasooran
2024-03-07 1:13 ` Andrew Lunn
2024-03-07 14:41 ` Parthiban.Veerasooran
2024-03-07 16:36 ` Andrew Lunn
2024-03-08 12:05 ` Parthiban.Veerasooran
2024-03-08 13:33 ` Andrew Lunn
2024-03-18 11:01 ` Parthiban.Veerasooran
2024-04-12 10:43 ` Parthiban.Veerasooran
2024-04-15 13:15 ` Andrew Lunn
2024-04-16 11:02 ` Parthiban.Veerasooran
2024-04-16 18:18 ` Andrew Lunn
2024-04-17 8:55 ` Parthiban.Veerasooran
2024-03-21 18:49 ` Selvamani Rajagopal
2024-03-22 5:50 ` Parthiban.Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 07/12] net: ethernet: oa_tc6: enable open alliance tc6 data communication Parthiban Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 08/12] net: ethernet: oa_tc6: implement transmit path to transfer tx ethernet frames Parthiban Veerasooran
2024-03-07 17:08 ` Andrew Lunn
2024-03-19 12:54 ` Parthiban.Veerasooran [this message]
2024-03-19 13:19 ` Andrew Lunn
2024-03-20 10:43 ` Parthiban.Veerasooran
2024-03-21 19:04 ` Selvamani Rajagopal
2024-03-21 19:42 ` Andrew Lunn
2024-03-22 18:31 ` Selvamani Rajagopal
2024-03-06 8:50 ` [PATCH net-next v3 09/12] net: ethernet: oa_tc6: implement receive path to receive rx " Parthiban Veerasooran
2024-03-08 0:14 ` Andrew Lunn
2024-03-19 12:54 ` Parthiban.Veerasooran
2024-03-19 13:20 ` Andrew Lunn
2024-03-20 5:55 ` Parthiban.Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 10/12] net: ethernet: oa_tc6: implement mac-phy interrupt Parthiban Veerasooran
2024-03-06 23:42 ` Woojung.Huh
2024-03-07 10:16 ` Parthiban.Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 11/12] microchip: lan865x: add driver support for Microchip's LAN865X MAC-PHY Parthiban Veerasooran
2024-03-06 23:44 ` Woojung.Huh
2024-03-07 9:13 ` Parthiban.Veerasooran
2024-03-06 8:50 ` [PATCH net-next v3 12/12] dt-bindings: net: add Microchip's LAN865X 10BASE-T1S MACPHY Parthiban Veerasooran
2024-03-06 18:16 ` Conor Dooley
2024-03-06 18:48 ` Andrew Lunn
2024-03-06 19:01 ` Conor Dooley
2024-03-20 8:40 ` Parthiban.Veerasooran
2024-03-20 9:53 ` Krzysztof Kozlowski
2024-03-21 8:38 ` Parthiban.Veerasooran
2024-03-21 8:40 ` Krzysztof Kozlowski
2024-03-21 12:00 ` Parthiban.Veerasooran
2024-03-21 15:34 ` Conor Dooley
2024-03-22 6:25 ` Parthiban.Veerasooran
2024-03-22 7:03 ` Krzysztof Kozlowski
2024-03-22 8:28 ` Parthiban.Veerasooran
2024-03-23 10:24 ` Krzysztof Kozlowski
2024-03-25 7:10 ` Parthiban.Veerasooran
2024-03-25 7:10 ` Parthiban.Veerasooran
2024-03-22 18:08 ` Conor Dooley
2024-03-25 7:12 ` Parthiban.Veerasooran
2024-03-20 8:40 ` Parthiban.Veerasooran
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