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Message-ID: <0605f176-5cdb-4f5b-9a6b-afa139c96732@iscas.ac.cn>
Date: Fri, 5 Sep 2025 23:45:29 +0800
From: Vivian Wang <wangruikang@...as.ac.cn>
To: Simon Horman <horms@...nel.org>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, Jakub Kicinski <kuba@...nel.org>,
Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Yixun Lan <dlan@...too.org>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Paolo Abeni <pabeni@...hat.com>, Philipp Zabel <p.zabel@...gutronix.de>,
Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
<palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Alexandre Ghiti <alex@...ti.fr>, Vadim Fedorenko
<vadim.fedorenko@...ux.dev>, Junhui Liu <junhui.liu@...moral.tech>,
Maxime Chevallier <maxime.chevallier@...tlin.com>, netdev@...r.kernel.org,
devicetree@...r.kernel.org, linux-riscv@...ts.infradead.org,
spacemit@...ts.linux.dev, linux-kernel@...r.kernel.org,
Troy Mitchell <troy.mitchell@...ux.spacemit.com>, Vivian Wang <uwu@...m.page>
Subject: Re: [PATCH net-next v9 2/5] net: spacemit: Add K1 Ethernet MAC
Hi Simon,
Thanks for the review.
(I have a question about the use of ndev->stats - see below.)
On 9/5/25 23:35, Simon Horman wrote:
> On Fri, Sep 05, 2025 at 07:09:31PM +0800, Vivian Wang wrote:
>> The Ethernet MACs found on SpacemiT K1 appears to be a custom design
>> that only superficially resembles some other embedded MACs. SpacemiT
>> refers to them as "EMAC", so let's just call the driver "k1_emac".
>>
>> Supports RGMII and RMII interfaces. Includes support for MAC hardware
>> statistics counters. PTP support is not implemented.
>>
>> Signed-off-by: Vivian Wang <wangruikang@...as.ac.cn>
>> Reviewed-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
>> Reviewed-by: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
>> Reviewed-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
>> Tested-by: Junhui Liu <junhui.liu@...moral.tech>
>> Tested-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
> ...
>
>> diff --git a/drivers/net/ethernet/spacemit/k1_emac.c b/drivers/net/ethernet/spacemit/k1_emac.c
> ...
>
>> +static void emac_init_hw(struct emac_priv *priv)
>> +{
>> + /* Destination address for 802.3x Ethernet flow control */
>> + u8 fc_dest_addr[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x01 };
>> +
>> + u32 rxirq = 0, dma = 0;
>> +
>> + regmap_set_bits(priv->regmap_apmu,
>> + priv->regmap_apmu_offset + APMU_EMAC_CTRL_REG,
>> + AXI_SINGLE_ID);
>> +
>> + /* Disable transmit and receive units */
>> + emac_wr(priv, MAC_RECEIVE_CONTROL, 0x0);
>> + emac_wr(priv, MAC_TRANSMIT_CONTROL, 0x0);
>> +
>> + /* Enable MAC address 1 filtering */
>> + emac_wr(priv, MAC_ADDRESS_CONTROL, MREGBIT_MAC_ADDRESS1_ENABLE);
>> +
>> + /* Zero initialize the multicast hash table */
>> + emac_wr(priv, MAC_MULTICAST_HASH_TABLE1, 0x0);
>> + emac_wr(priv, MAC_MULTICAST_HASH_TABLE2, 0x0);
>> + emac_wr(priv, MAC_MULTICAST_HASH_TABLE3, 0x0);
>> + emac_wr(priv, MAC_MULTICAST_HASH_TABLE4, 0x0);
>> +
>> + /* Configure thresholds */
>> + emac_wr(priv, MAC_TRANSMIT_FIFO_ALMOST_FULL, DEFAULT_TX_ALMOST_FULL);
>> + emac_wr(priv, MAC_TRANSMIT_PACKET_START_THRESHOLD,
>> + DEFAULT_TX_THRESHOLD);
>> + emac_wr(priv, MAC_RECEIVE_PACKET_START_THRESHOLD, DEFAULT_RX_THRESHOLD);
>> +
>> + /* Configure flow control (enabled in emac_adjust_link() later) */
>> + emac_set_mac_addr_reg(priv, fc_dest_addr, MAC_FC_SOURCE_ADDRESS_HIGH);
>> + emac_wr(priv, MAC_FC_PAUSE_HIGH_THRESHOLD, DEFAULT_FC_FIFO_HIGH);
>> + emac_wr(priv, MAC_FC_HIGH_PAUSE_TIME, DEFAULT_FC_PAUSE_TIME);
>> + emac_wr(priv, MAC_FC_PAUSE_LOW_THRESHOLD, 0);
>> +
>> + /* RX IRQ mitigation */
>> + rxirq = EMAC_RX_FRAMES & MREGBIT_RECEIVE_IRQ_FRAME_COUNTER_MASK;
>> + rxirq |= (EMAC_RX_COAL_TIMEOUT
>> + << MREGBIT_RECEIVE_IRQ_TIMEOUT_COUNTER_SHIFT) &
>> + MREGBIT_RECEIVE_IRQ_TIMEOUT_COUNTER_MASK;
> Probably this driver can benefit from using FIELD_PREP and FIELD_GET
> in a number of places. In this case I think it would mean that
> MREGBIT_RECEIVE_IRQ_TIMEOUT_COUNTER_SHIFT can be removed entirely.
That looks useful. There's a few more uses of *_SHIFT in this driver,
and I think I can get them all to use FIELD_PREP. I'll change those in
the next version.
>> +
>> + rxirq |= MREGBIT_RECEIVE_IRQ_MITIGATION_ENABLE;
>> + emac_wr(priv, DMA_RECEIVE_IRQ_MITIGATION_CTRL, rxirq);
> ...
>
>> +/* Returns number of packets received */
>> +static int emac_rx_clean_desc(struct emac_priv *priv, int budget)
>> +{
>> + struct net_device *ndev = priv->ndev;
>> + struct emac_rx_desc_buffer *rx_buf;
>> + struct emac_desc_ring *rx_ring;
>> + struct sk_buff *skb = NULL;
>> + struct emac_desc *rx_desc;
>> + u32 got = 0, skb_len, i;
>> + int status;
>> +
>> + rx_ring = &priv->rx_ring;
>> +
>> + i = rx_ring->tail;
>> +
>> + while (budget--) {
>> + rx_desc = &((struct emac_desc *)rx_ring->desc_addr)[i];
>> +
>> + /* Stop checking if rx_desc still owned by DMA */
>> + if (READ_ONCE(rx_desc->desc0) & RX_DESC_0_OWN)
>> + break;
>> +
>> + dma_rmb();
>> +
>> + rx_buf = &rx_ring->rx_desc_buf[i];
>> +
>> + if (!rx_buf->skb)
>> + break;
>> +
>> + got++;
>> +
>> + dma_unmap_single(&priv->pdev->dev, rx_buf->dma_addr,
>> + rx_buf->dma_len, DMA_FROM_DEVICE);
>> +
>> + status = emac_rx_frame_status(priv, rx_desc);
>> + if (unlikely(status == RX_FRAME_DISCARD)) {
>> + ndev->stats.rx_dropped++;
> As per the comment in struct net-device,
> ndev->stats should not be used in modern drivers.
>
> Probably you want to implement NETDEV_PCPU_STAT_TSTATS.
>
> Sorry for not mentioning this in an earlier review of
> stats in this driver.
>
On a closer look, these counters in ndev->stats seems to be redundant
with the hardware-tracked statistics, so maybe I should just not bother
with updating ndev->stats. Does that make sense?
Thanks,
Vivian "dramforever" Wang
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