From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.tipi-net.de (mail.tipi-net.de [194.13.80.246]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2F581347C5; Sun, 19 Jul 2026 10:53:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=194.13.80.246 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784458416; cv=none; b=dXi/qWo+s53Pf+ggMWfX6xgAKuWe9PmdrJmPk7FJmAA1SHqdhS2edEWk//VyIrEb45XvrdOoJ5dsC4//fSH+XkX0jVv39skJRUzlI9y5t/2B/6q2m07+fLD4Ie3+sMbe+47i8TE+LlRGDmDqk+1vxc9MHgULbDXrA9TsYzzcITU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784458416; c=relaxed/simple; bh=YGEazFIrGT/VpeToepKfs778xpaRjiZ9+Sva2iioD+Y=; h=MIME-Version:Date:From:To:Cc:Subject:In-Reply-To:References: Message-ID:Content-Type; b=reRm4KO/AT5s+qW3VuiL9itkcnsXS2j7mDUb3VDVnbluJ3zaniV/bD8ilDXRkBXRRDplAcQYerqLsGHmXeludm4tOlsM0wYURa87M9+jX31Mt/bc3d/IGpEzkCDCTG1Ex4TLXty+2FTFcF6N7fEdxxc/pfCedPyMXOgwh346WWY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tipi-net.de; spf=pass smtp.mailfrom=tipi-net.de; dkim=pass (2048-bit key) header.d=tipi-net.de header.i=@tipi-net.de header.b=AEvqezzC; arc=none smtp.client-ip=194.13.80.246 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tipi-net.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=tipi-net.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=tipi-net.de header.i=@tipi-net.de header.b="AEvqezzC" Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 9E72DA0292; Sun, 19 Jul 2026 12:53:31 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tipi-net.de; s=dkim; t=1784458412; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=YF9fV7bCEO9HdEc94h+7cPm3p4Ue0YkXnFcoaE08TDk=; b=AEvqezzCPLo2bM7S2YOo01pOCKlaIR7Y7TuIV/PrYA2vPO4KTXnc6Pf0QfKUNCB5eneA+n xdkMBa1+s2V1T1G+tWRx3iFlPMlKzRBEocWxLi/XKs6OTqH7ndDZHuW9JNZ+HnfInafKHS w1zhCBftWPA6HY576YrkRVriY8JmzXKqrSAXa49QUEmpqCC5mDVf6NpmA5aceOT7bOMk2x Rbu4GJdmCWXMu2kWC7JAjqSFy0g9VDAof2AUSsZhRHTs5DlFRbwuOq951s+xytstY9HnUJ QKsNNfkXDjSFgiHO1DipEsqyfhmGy6vFJTcSbGOtrqaOHlR9yOQayK2y+EqyoQ== Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Sun, 19 Jul 2026 12:53:31 +0200 From: Nicolai Buchwitz To: =?UTF-8?Q?Th=C3=A9o_Lebrun?= Cc: Conor Dooley , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Richard Cochran , Russell King , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Nicolas Ferre , Claudiu Beznea , Paolo Valerio , Vladimir Kondratiev , Gregory CLEMENT , =?UTF-8?Q?Beno=C3=AEt_Monin?= , Tawfik Bayouk , Thomas Petazzoni , Maxime Chevallier Subject: Re: [PATCH net-next v4 14/15] net: macb: use context swapping in .set_ringparam() In-Reply-To: <20260717-macb-context-v4-14-0acbe7f10cdb@bootlin.com> References: <20260717-macb-context-v4-0-0acbe7f10cdb@bootlin.com> <20260717-macb-context-v4-14-0acbe7f10cdb@bootlin.com> Message-ID: X-Sender: nb@tipi-net.de Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Last-TLS-Session-Version: TLSv1.3 Hi Théo On 17.7.2026 21:48, Théo Lebrun wrote: > ethtool_ops.set_ringparam() is implemented using the primitive close / > update ring size / reopen sequence. Under memory pressure this does not > fly: we free our buffers at close and cannot reallocate new ones at > open. Also, it triggers a slow PHY reinit. > > Instead, exploit the new context mechanism and improve our sequence to: > - allocate a new context (including buffers) first > - if it fails, early return without any impact to the interface > - stop interface > - update global state (bp, netdev, etc) > - pass buffer pointers to the hardware > - start interface > - free old context. > > The HW disable sequence is inspired by macb_reset_hw() but avoids > (1) setting NCR bit CLRSTAT and (2) clearing register PBUFRXCUT. > > The HW re-enable sequence is inspired by macb_mac_link_up(), skipping > over register writes which would be redundant (because values have not > changed). > > The generic context swapping parts are isolated into helper functions > macb_context_swap_start|end(), reusable by other operations > (change_mtu, > set_channels, etc). > > Introduce a new locking primitive (mac_cfg_lock mutex) to serialise > swap > with phylink MAC callbacks. Avoid stopping phylink to avoid a slow PHY > retrain. Those callbacks grab phydev->lock if it exists so we could > imagine grabbing that from the swap op, but phydev->lock doesn't exist > in the SFP case. > > AT91 EMAC is handled differently as their buffer management is separate > and they don't do NAPI. We refuse them (-EBUSY) to avoid implementing > context swapping for them. > > Signed-off-by: Théo Lebrun > --- > drivers/net/ethernet/cadence/macb.h | 5 + > drivers/net/ethernet/cadence/macb_main.c | 162 > +++++++++++++++++++++++++++++-- > 2 files changed, 158 insertions(+), 9 deletions(-) > > diff --git a/drivers/net/ethernet/cadence/macb.h > b/drivers/net/ethernet/cadence/macb.h > index ac2f2d8065d7..93e513cf1fbb 100644 > --- a/drivers/net/ethernet/cadence/macb.h > +++ b/drivers/net/ethernet/cadence/macb.h > @@ -1361,6 +1361,8 @@ struct macb { > struct macb_queue queues[MACB_MAX_QUEUES]; > > spinlock_t lock; > + /* Serializes context swap against phylink MAC callbacks. */ > + struct mutex mac_cfg_lock; > struct clk *pclk; > struct clk *hclk; > struct clk *tx_clk; > @@ -1421,6 +1423,9 @@ struct macb { > struct delayed_work tx_lpi_work; > u32 tx_lpi_timer; > > + /* ISR must not drive NAPI & BH mechanisms. Protected by bp->lock. */ > + bool ctx_swap; > + > u32 rx_intr_mask; > > struct macb_pm_data pm_data; > diff --git a/drivers/net/ethernet/cadence/macb_main.c > b/drivers/net/ethernet/cadence/macb_main.c > index c832b6c1b98c..5792647eb0a6 100644 > --- a/drivers/net/ethernet/cadence/macb_main.c > +++ b/drivers/net/ethernet/cadence/macb_main.c > [...] > + > + for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) { > + /* Must be done before NAPI is disabled. */ > + cancel_work_sync(&queue->tx_error_task); > + > + napi_disable(&queue->napi_rx); > + napi_disable(&queue->napi_tx); > + netdev_tx_reset_queue(netdev_get_tx_queue(bp->netdev, q)); > + } > + > + /* Must be done after napi_tx is disabled. */ > + cancel_delayed_work_sync(&bp->tx_lpi_work); > + > + /* Can finally disable software Tx; need to wait until napi_tx and > + * tx_error_task cannot be scheduled as either might wakeup Tx. > + */ > + netif_tx_disable(bp->netdev); Shouldn't netdev_tx_reset_queue() come after netif_tx_disable()? Tx is still running here, so an xmit right after the reset adds bytes to the DQL that never get completed (macb_free() frees the old skbs without netdev_tx_completed_queue()). Not sure, but that could leave the queue stopped by BQL forever? > [...] Thanks Nicolai