Messages in this thread | | | From | Kai-Heng Feng <> | Date | Thu, 12 May 2022 10:55:50 +0800 | Subject | Re: [Intel-wired-lan] [PATCH 2/2] igb: Make DMA faster when CPU is active on the PCIe link |
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Hi Paul,
On Wed, May 11, 2022 at 8:49 PM Paul Menzel <pmenzel@molgen.mpg.de> wrote: > > Dear Kai-Hang, > > > Thank you for the patch. > > > Am 11.05.22 um 14:28 schrieb Kai-Heng Feng: > > We found Intel I210 can only achieve ~750Mbps Tx speed on some > > platforms. The RR2DCDELAY shows around 0x2xxx DMA delay, which will be > > Please give an example platform, where it works and where it does not.
The platform is about but not yet hit the market yet, so I can't disclose it. They are Intel Alder Lake based.
> > How did you test transfer speed?
Iperf.
> > > significantly lower when 1) ASPM is disabled or 2) SoC package c-state > > stays above PC3. When the RR2DCDELAY is around 0x1xxx the Tx speed can > > reach to ~950Mbps. > > > > According to the I210 datasheet "8.26.1 PCIe Misc. Register - PCIEMISC", > > "DMA Idle Indication" doesn't seem to tie to DMA coalesce anymore, so > > set it to 1b for "DMA is considered idle when there is no Rx or Tx AND > > when there are no TLPs indicating that CPU is active detected on the > > PCIe link (such as the host executes CSR or Configuration register read > > or write operation)" and performing Tx should also fall under "active > > CPU on PCIe link" case. > > > > In addition to that, commit b6e0c419f040 ("igb: Move DMA Coalescing init > > code to separate function.") seems to wrongly changed from enabling > > E1000_PCIEMISC_LX_DECISION to disabling it, also fix that. > > Please split this into a separate commit with Fixes tag, and maybe the > commit author in Cc.
I don't see the need to split to separate commit as both require the same change.
I will add the "Fixes" tag once the igb maintainers reviewed the patch.
Kai-Heng
> > > Kind regards, > > Paul > > > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com> > > --- > > drivers/net/ethernet/intel/igb/igb_main.c | 12 +++++------- > > 1 file changed, 5 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c > > index 34b33b21e0dcd..eca797dded429 100644 > > --- a/drivers/net/ethernet/intel/igb/igb_main.c > > +++ b/drivers/net/ethernet/intel/igb/igb_main.c > > @@ -9897,11 +9897,10 @@ static void igb_init_dmac(struct igb_adapter *adapter, u32 pba) > > struct e1000_hw *hw = &adapter->hw; > > u32 dmac_thr; > > u16 hwm; > > + u32 reg; > > > > if (hw->mac.type > e1000_82580) { > > if (adapter->flags & IGB_FLAG_DMAC) { > > - u32 reg; > > - > > /* force threshold to 0. */ > > wr32(E1000_DMCTXTH, 0); > > > > @@ -9934,7 +9933,6 @@ static void igb_init_dmac(struct igb_adapter *adapter, u32 pba) > > /* Disable BMC-to-OS Watchdog Enable */ > > if (hw->mac.type != e1000_i354) > > reg &= ~E1000_DMACR_DC_BMC2OSW_EN; > > - > > wr32(E1000_DMACR, reg); > > > > /* no lower threshold to disable > > @@ -9951,12 +9949,12 @@ static void igb_init_dmac(struct igb_adapter *adapter, u32 pba) > > */ > > wr32(E1000_DMCTXTH, (IGB_MIN_TXPBSIZE - > > (IGB_TX_BUF_4096 + adapter->max_frame_size)) >> 6); > > + } > > > > - /* make low power state decision controlled > > - * by DMA coal > > - */ > > + if (hw->mac.type >= e1000_i210 || > > + (adapter->flags & IGB_FLAG_DMAC)) { > > reg = rd32(E1000_PCIEMISC); > > - reg &= ~E1000_PCIEMISC_LX_DECISION; > > + reg |= E1000_PCIEMISC_LX_DECISION; > > wr32(E1000_PCIEMISC, reg); > > } /* endif adapter->dmac is not disabled */ > > } else if (hw->mac.type == e1000_82580) {
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