Re: [PATCH net-next] net: stmmac: fpe: Keep pmac always enabled
From: Nazle Asmade, Muhammad Nazim Amirul
Date: Tue Jul 28 2026 - 22:49:23 EST
On 28/7/2026 3:18 pm, Nazle Asmade, Muhammad Nazim Amirul wrote:
> On 27/7/2026 4:11 pm, Maxime Chevallier wrote:
>> Hi,
>>
>> On 7/27/26 07:13, muhammad.nazim.amirul.nazle.asmade@xxxxxxxxxx wrote:
>>> From: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@xxxxxxxxxx>
>>>
>>> The preemptive MAC in DWMAC is always enabled, meaning DWMAC is always
>>> ready to receive preemptive mPackets. Keep pmac_enabled true at init
>>> time and reject attempts to disable it via ethtool set_mm.
>>>
>>> The FPE residual queue (fprq) controls which Rx queue receives residual
>>> preemptive mPackets from the pmac. Move its configuration from
>>> stmmac_fpe_configure_tx() to stmmac_fpe_configure_pmac() where it
>>> logically belongs.
>>>
>>> Also add a missing return in stmmac_fpe_init() so that the pmac_enabled
>>> initialization is not reached on hardware where FPE is not supported by
>>> the driver.
>>
>> Can you split this up into individual patches, one for the
>> stmmac_set_mm() and
>> stmmac_fpe_init() to validate that we keep pmac on, one for the
>> missing return,
>> and one for the pmac configuration in the right fonction ?
>
> sure will split as per your suggestion>
>> Also one comment bellow :>
>>> Signed-off-by: Rohan G Thomas <rohan.g.thomas@xxxxxxxxxx>
>>> Signed-off-by: Nazim Amirul
>>> <muhammad.nazim.amirul.nazle.asmade@xxxxxxxxxx>
>>> ---
>>> .../ethernet/stmicro/stmmac/stmmac_ethtool.c | 7 ++++
>>> .../net/ethernet/stmicro/stmmac/stmmac_fpe.c | 34 ++++++++++++-------
>>> 2 files changed, 29 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c b/
>>> drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
>>> index 92585d27ab88..8ebdd249e5c8 100644
>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
>>> @@ -1064,6 +1064,13 @@ static int stmmac_set_mm(struct net_device
>>> *ndev, struct ethtool_mm_cfg *cfg,
>>> if (err)
>>> return err;
>>> + if (!priv->dma_cap.fpesel)
>>> + return -EOPNOTSUPP;
>>> +
>>> + /* DWMAC always have preemptible MAC enabled */
>>> + if (!cfg->pmac_enabled)
>>> + return -EINVAL;
>>> +
>>> stmmac_fpe_set_add_frag_size(priv, frag_size);
>>> ethtool_mmsv_set_mm(&priv->fpe_cfg.mmsv, cfg);
>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c b/
>>> drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
>>> index c54c70224351..2bfa84ad04a6 100644
>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_fpe.c
>>> @@ -47,20 +47,13 @@ static void stmmac_fpe_configure_tx(struct
>>> ethtool_mmsv *mmsv, bool tx_enable)
>>> struct stmmac_fpe_cfg *cfg = container_of(mmsv, struct
>>> stmmac_fpe_cfg, mmsv);
>>> struct stmmac_priv *priv = container_of(cfg, struct
>>> stmmac_priv, fpe_cfg);
>>> const struct stmmac_fpe_reg *reg = cfg->reg;
>>> - u32 num_rxq = priv->plat->rx_queues_to_use;
>>> void __iomem *ioaddr = priv->ioaddr;
>>> - u32 value;
>>> - if (tx_enable) {
>>> + if (tx_enable)
>>> cfg->fpe_csr = STMMAC_MAC_FPE_CTRL_STS_EFPE;
>>> - value = readl(ioaddr + reg->rxq_ctrl1_reg);
>>> - value &= ~reg->fprq_mask;
>>> - /* Keep this SHIFT, FIELD_PREP() expects a constant mask :-/ */
>>> - value |= (num_rxq - 1) << __ffs(reg->fprq_mask);
>>> - writel(value, ioaddr + reg->rxq_ctrl1_reg);
>>> - } else {
>>> + else
>>> cfg->fpe_csr = 0;
>>> - }
>>> +
>>> writel(cfg->fpe_csr, ioaddr + reg->mac_fpe_reg);
>>> }
>>> @@ -68,10 +61,11 @@ static void stmmac_fpe_configure_pmac(struct
>>> ethtool_mmsv *mmsv, bool pmac_enabl
>>> {
>>> struct stmmac_fpe_cfg *cfg = container_of(mmsv, struct
>>> stmmac_fpe_cfg, mmsv);
>>> struct stmmac_priv *priv = container_of(cfg, struct
>>> stmmac_priv, fpe_cfg);
>>> + u32 num_rxq = priv->plat->rx_queues_to_use;
>>> const struct stmmac_fpe_reg *reg = cfg->reg;
>>> void __iomem *ioaddr = priv->ioaddr;
>>> unsigned long flags;
>>> - u32 value;
>>> + u32 value, value_2;
>>> spin_lock_irqsave(&priv->hw->irq_ctrl_lock, flags);
>>> value = readl(ioaddr + reg->int_en_reg);
>>> @@ -83,6 +77,14 @@ static void stmmac_fpe_configure_pmac(struct
>>> ethtool_mmsv *mmsv, bool pmac_enabl
>>> value |= reg->int_en_bit;
>>> }
>>> + /* Frame Preemption Residue Queue is the Rx Queue to which
>>> + * residual preemptive mPackets must be forwarded from the
>>> pmac.
>>> + */
>>> + value_2 = readl(ioaddr + reg->rxq_ctrl1_reg);
>>> + value_2 &= ~reg->fprq_mask;
>>> + /* Keep this SHIFT, FIELD_PREP() expects a constant mask :-/ */
>>
>> you can use u32_replace_bits for non constant expr :
> will update and repost it, Thanks Maxime!>
>> https://nam10.safelinks.protection.outlook.com/?
>> url=https%3A%2F%2Felixir.bootlin.com%2Flinux%2Fv7.2-
>> rc4%2Fsource%2Finclude%2Flinux%2Fbitfield.h%23L236&data=05%7C02%7Cmuhammad.nazim.amirul.nazle.asmade%40altera.com%7Ccc409a6e8ac34d18f82d08deebb6b578%7Cfbd72e03d4a54110adce614d51f2077a%7C0%7C0%7C639207367157805862%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=blOrVXSlgOqDnVPdnNnLXXdrIhz9iVeb98SAp2kI3AQ%3D&reserved=0
>>
>> (it's autogenerated and not documented, hence very hard to find IMO)
>>
>> Maxime
>
Hi Maxime,
You may refer to the lore below,
https://lore.kernel.org/all/20260729015247.25774-1-muhammad.nazim.amirul.nazle.asmade@xxxxxxxxxx/
Hope this is the expectation, Thanks!