netdev - Re: [PATCH net-next] net: stmmac: Simplify mtl IRQ status checking

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Date: Thu, 8 Feb 2024 15:52:27 +0100
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Kurt Kanzenbach <kurt@...utronix.de>
CC: Alexandre Torgue <alexandre.torgue@...s.st.com>, Jose Abreu
	<joabreu@...opsys.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, Maxime Coquelin <mcoquelin.stm32@...il.com>, "Yannick
 Vignon" <yannick.vignon@....com>, Sebastian Andrzej Siewior
	<bigeasy@...utronix.de>, <netdev@...r.kernel.org>,
	<linux-stm32@...md-mailman.stormreply.com>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH net-next] net: stmmac: Simplify mtl IRQ status checking

On Thu, Feb 08, 2024 at 03:32:30PM +0100, Kurt Kanzenbach wrote:
> On Thu Feb 08 2024, Maciej Fijalkowski wrote:
> > On Thu, Feb 08, 2024 at 11:35:25AM +0100, Kurt Kanzenbach wrote:
> >> Commit 8a7cb245cf28 ("net: stmmac: Do not enable RX FIFO overflow
> >> interrupts") disabled the RX FIFO overflow interrupts. However, it left the
> >> status variable around, but never checks it.
> >> 
> >> As stmmac_host_mtl_irq_status() returns only 0 now, the code can be
> >> simplified.
> >> 
> >> Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
> >> ---
> >>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 6 ++----
> >>  1 file changed, 2 insertions(+), 4 deletions(-)
> >> 
> >> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >> index 04d817dc5899..10ce2f272b62 100644
> >> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >> @@ -6036,10 +6036,8 @@ static void stmmac_common_interrupt(struct stmmac_priv *priv)
> >>  				priv->tx_path_in_lpi_mode = false;
> >>  		}
> >>  
> >> -		for (queue = 0; queue < queues_count; queue++) {
> >> -			status = stmmac_host_mtl_irq_status(priv, priv->hw,
> >> -							    queue);
> >> -		}
> >> +		for (queue = 0; queue < queues_count; queue++)
> >> +			stmmac_host_mtl_irq_status(priv, priv->hw, queue);
> >
> > Hey Kurt,
> >
> > looks to me that all of the current callbacks just return 0 so why not
> > make them return void instead?
> 
> Well, there are two callbacks of this in dwmac4 and dwxgmac2. Both of
> them still have the code for handling the overflow interrupt (and then
> returning != 0). However, as of commit 8a7cb245cf28 the interrupt
> shouldn't fire. So yes, it could be changed to void along with some
> code removal. But, maybe i'm missing something.

Hmm, ok, my 'quick' glance over the code was too quick :) I missed
overflow encoding to ret within callbacks, sorry. But it seems that even
though they can return nonzero values they would be ignored, correct?

> 
> Thanks,
> Kurt