Messages in this thread |  | | Date | Tue, 25 Nov 2025 19:05:47 +0100 | | Subject | Re: [PATCH net-next] net: stmmac: dwmac: Disable flushing frames on Rx Buffer Unavailable | | From | Maxime Chevallier <> |
| |
Hi,
On 25/11/2025 17:37, Rohan G Thomas via B4 Relay wrote: > From: Rohan G Thomas <rohan.g.thomas@altera.com> > > In Store and Forward mode, flushing frames when the receive buffer is > unavailable, can cause the MTL Rx FIFO to go out of sync. This results > in buffering of a few frames in the FIFO without triggering Rx DMA > from transferring the data to the system memory until another packet > is received. Once the issue happens, for a ping request, the packet is > forwarded to the system memory only after we receive another packet > and hece we observe a latency equivalent to the ping interval. > > 64 bytes from 192.168.2.100: seq=1 ttl=64 time=1000.344 ms > > Also, we can observe constant gmacgrp_debug register value of > 0x00000120, which indicates "Reading frame data". > > The issue is not reproducible after disabling frame flushing when Rx > buffer is unavailable. But in that case, the Rx DMA enters a suspend > state due to buffer unavailability. To resume operation, software > must write to the receive_poll_demand register after adding new > descriptors, which reactivates the Rx DMA. > > This issue is observed in the socfpga platforms which has dwmac1000 IP > like Arria 10, Cyclone V and Agilex 7. Issue is reproducible after > running iperf3 server at the DUT for UDP lower packet sizes. > > Signed-off-by: Rohan G Thomas <rohan.g.thomas@altera.com> > Reviewed-by: Matthew Gerlach <matthew.gerlach@altera.com>
I'll let others comment on the correctness of the dwmac1000 part, but still :
Tested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Maxime
> --- > drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c | 5 +++-- > drivers/net/ethernet/stmicro/stmmac/dwmac_dma.h | 1 + > drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c | 5 +++++ > drivers/net/ethernet/stmicro/stmmac/hwif.h | 3 +++ > drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 ++ > 5 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c > index 6d9b8fac3c6d0fd76733ab4a1a8cce2420fa40b4..5877fec9f6c30ed18cdcf5398816e444e0bd0091 100644 > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c > @@ -135,10 +135,10 @@ static void dwmac1000_dma_operation_mode_rx(struct stmmac_priv *priv, > > if (mode == SF_DMA_MODE) { > pr_debug("GMAC: enable RX store and forward mode\n"); > - csr6 |= DMA_CONTROL_RSF; > + csr6 |= DMA_CONTROL_RSF | DMA_CONTROL_DFF; > } else { > pr_debug("GMAC: disable RX SF mode (threshold %d)\n", mode); > - csr6 &= ~DMA_CONTROL_RSF; > + csr6 &= ~(DMA_CONTROL_RSF | DMA_CONTROL_DFF); > csr6 &= DMA_CONTROL_TC_RX_MASK; > if (mode <= 32) > csr6 |= DMA_CONTROL_RTC_32; > @@ -262,6 +262,7 @@ const struct stmmac_dma_ops dwmac1000_dma_ops = { > .dma_rx_mode = dwmac1000_dma_operation_mode_rx, > .dma_tx_mode = dwmac1000_dma_operation_mode_tx, > .enable_dma_transmission = dwmac_enable_dma_transmission, > + .enable_dma_reception = dwmac_enable_dma_reception, > .enable_dma_irq = dwmac_enable_dma_irq, > .disable_dma_irq = dwmac_disable_dma_irq, > .start_tx = dwmac_dma_start_tx, > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac_dma.h b/drivers/net/ethernet/stmicro/stmmac/dwmac_dma.h > index d1c149f7a3dd9e472b237101666e11878707f0f2..054ecb20ce3f68bce5da3efaf36acf33e430d3f0 100644 > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac_dma.h > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac_dma.h > @@ -169,6 +169,7 @@ static inline u32 dma_chan_base_addr(u32 base, u32 chan) > #define NUM_DWMAC4_DMA_REGS 27 > > void dwmac_enable_dma_transmission(void __iomem *ioaddr, u32 chan); > +void dwmac_enable_dma_reception(void __iomem *ioaddr, u32 chan); > void dwmac_enable_dma_irq(struct stmmac_priv *priv, void __iomem *ioaddr, > u32 chan, bool rx, bool tx); > void dwmac_disable_dma_irq(struct stmmac_priv *priv, void __iomem *ioaddr, > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c b/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c > index 467f1a05747ecf0be5b9f3392cd3d2049d676c21..97a803d68e3a2f120beaa7c3254748cf404236df 100644 > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c > @@ -33,6 +33,11 @@ void dwmac_enable_dma_transmission(void __iomem *ioaddr, u32 chan) > writel(1, ioaddr + DMA_CHAN_XMT_POLL_DEMAND(chan)); > } > > +void dwmac_enable_dma_reception(void __iomem *ioaddr, u32 chan) > +{ > + writel(1, ioaddr + DMA_CHAN_RCV_POLL_DEMAND(chan)); > +} > + > void dwmac_enable_dma_irq(struct stmmac_priv *priv, void __iomem *ioaddr, > u32 chan, bool rx, bool tx) > { > diff --git a/drivers/net/ethernet/stmicro/stmmac/hwif.h b/drivers/net/ethernet/stmicro/stmmac/hwif.h > index f257ce4b6c66e0bbd3180d54ac7f5be934153a6b..df6e8a567b1f646f83effbb38d8e53441a6f6150 100644 > --- a/drivers/net/ethernet/stmicro/stmmac/hwif.h > +++ b/drivers/net/ethernet/stmicro/stmmac/hwif.h > @@ -201,6 +201,7 @@ struct stmmac_dma_ops { > void (*dma_diagnostic_fr)(struct stmmac_extra_stats *x, > void __iomem *ioaddr); > void (*enable_dma_transmission)(void __iomem *ioaddr, u32 chan); > + void (*enable_dma_reception)(void __iomem *ioaddr, u32 chan); > void (*enable_dma_irq)(struct stmmac_priv *priv, void __iomem *ioaddr, > u32 chan, bool rx, bool tx); > void (*disable_dma_irq)(struct stmmac_priv *priv, void __iomem *ioaddr, > @@ -261,6 +262,8 @@ struct stmmac_dma_ops { > stmmac_do_void_callback(__priv, dma, dma_diagnostic_fr, __args) > #define stmmac_enable_dma_transmission(__priv, __args...) \ > stmmac_do_void_callback(__priv, dma, enable_dma_transmission, __args) > +#define stmmac_enable_dma_reception(__priv, __args...) \ > + stmmac_do_void_callback(__priv, dma, enable_dma_reception, __args) > #define stmmac_enable_dma_irq(__priv, __args...) \ > stmmac_do_void_callback(__priv, dma, enable_dma_irq, __priv, __args) > #define stmmac_disable_dma_irq(__priv, __args...) \ > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > index 6cacedb2c9b3fefdd4c9ec8ba98d389443d21ebd..1ecca60baf74286da7f156b4c3c835b3cbabf1ba 100644 > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > @@ -4973,6 +4973,8 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv, u32 queue) > rx_q->rx_tail_addr = rx_q->dma_rx_phy + > (rx_q->dirty_rx * sizeof(struct dma_desc)); > stmmac_set_rx_tail_ptr(priv, priv->ioaddr, rx_q->rx_tail_addr, queue); > + /* Wake up Rx DMA from the suspend state if required */ > + stmmac_enable_dma_reception(priv, priv->ioaddr, queue); > } > > static unsigned int stmmac_rx_buf1_len(struct stmmac_priv *priv, > > --- > base-commit: e3daf0e7fe9758613bec324fd606ed9caa187f74 > change-id: 20251125-a10_ext_fix-5951805b9906 > > Best regards,
|  |