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

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Date: Thu, 08 Feb 2024 16:08:00 +0100
From: Kurt Kanzenbach <kurt@...utronix.de>
To: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
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, Maciej Fijalkowski wrote:
> 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?

Yeah, they are ignored.

Thanks,
Kurt

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