linux-kernel - Re: [PATCH v2] net: ethernet: mtk_eth

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Message-ID: <aE6cyHC39IV27PcF@lore-desk>
Date: Sun, 15 Jun 2025 12:13:28 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: "Frank Wunderlich (linux)" <linux@...web.de>
Cc: Daniel Golle <daniel@...rotopia.org>, Felix Fietkau <nbd@....name>,
	Sean Wang <sean.wang@...iatek.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Frank Wunderlich <frank-w@...lic-files.de>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, Simon Horman <horms@...nel.org>
Subject: Re: [PATCH v2] net: ethernet: mtk_eth_soc: support named IRQs

> Am 2025-06-15 10:57, schrieb Lorenzo Bianconi:
> > > From: Frank Wunderlich <frank-w@...lic-files.de>
> > > 
> > > Add named interrupts and keep index based fallback for exiting
> > > devicetrees.
> > > 
> > > Currently only rx and tx IRQs are defined to be used with mt7988, but
> > > later extended with RSS/LRO support.
> > > 
> > > Signed-off-by: Frank Wunderlich <frank-w@...lic-files.de>
> > > Reviewed-by: Simon Horman <horms@...nel.org>
> > 
> > Hi Frank,
> > 
> > I guess my comments on v1 apply even in v2. Can you please take a look?

sure

> 
> adding your comments (and mine as context) from v1 here:
> 
> Am 2025-06-15 10:57, schrieb Lorenzo Bianconi:
> > > From: Frank Wunderlich <frank-w@...lic-files.de>
> 
> > > I had to leave flow compatible with this:
> > > 
> > > <https://github.com/frank-w/BPI-Router-Linux/blob/bd7e1983b9f0a69cf47cc9b9631138910d6c1d72/drivers/net/ethernet/mediatek/mtk_eth_soc.c#L5176>
> > 
> > I guess the best would be to start from 0 even here (and wherever it is
> > necessary) and avoid reading current irq[0] since it is not actually
> > used for
> > !shared_int devices (e.g. MT7988).  Agree?
> > 
> > > 
> > > Here the irqs are taken from index 1 and 2 for
> > >  registration (!shared_int else only 0). So i avoided changing the
> > >  index,but yes index 0 is unset at this time.
> > > 
> > > I guess the irq0 is not really used here...
> > > I tested the code on bpi-r4 and have traffic
> > >  rx+tx and no crash.
> > >  imho this field is not used on !shared_int
> > >  because other irq-handlers are used and
> > >  assigned in position above.
> > 
> > agree. I have not reviewed the code in detail, but this is why
> > I think we can avoid reading it.
> 
> i areee, but imho it should be a separate patch because these are 2
> different changes

I am fine to have it in a separate patch but I would prefer to have this patch
in the same series, I think it is more clear.

> 
> > > It looks like the irq[0] is read before...there is a
> > >  message printed for mediatek frame engine
> > >  which uses index 0 and shows an irq 102 on
> > >  index way and 0 on named version...but the
> > >  102 in index way is not visible in /proc/interrupts.
> > > So imho this message is misleading.
> > > 
> > > Intention for this patch is that irq 0 and 3 on
> > >  mt7988 (sdk) are reserved (0 is skipped on
> > > !shared_int and 3 never read) and should imho
> > >  not listed in devicetree. For further cleaner
> > >  devicetrees (with only needed irqs) and to
> > >  extend additional irqs for rss/lro imho irq
> > >  names make it better readable.
> > 
> > Same here, if you are not listing them in the device tree, you can
> > remove them
> > in the driver too (and adjust the code to keep the backward
> > compatibility).
> 
> afaik i have no SHARED_INT board (only mt7621, mt7628) so changing the
> index-logic will require testing on such boards too.

I think the change will not heavily impact SHARED_INT devices.

Regards,
Lorenzo

> 
> i looked a bit into it and see mt7623 and mt7622 have 3 IRQs defined
> (!SHARED_INT) and i'm not 100% sure if the first is also skipped (as far as
> i understood code it should always be skipped).
> 
> In the end i would change the irq-index part in separate patch once this is
> accepted to have clean changes and not mixing index with names (at least to
> allow a revert of second in case of regression).
> 
> Am 2025-06-15 11:26, schrieb Daniel Golle:
> > In addition to Lorenzo's comment to reduce the array to the actually
> > used
> > IRQs, I think it would be nice to introduce precompiler macros for the
> > irq
> > array index, ie. once the array is reduce to size 2 it could be
> > something
> > like
> > 
> > #define MTK_ETH_IRQ_SHARED 0
> > #define MTK_ETH_IRQ_TX 0
> > #define MTK_ETH_IRQ_RX 1
> > #define __MTK_ETH_IRQ_MAX MTK_ETH_IRQ_RX
> > 
> > That would make all the IRQ code more readable than having to deal with
> > numerical values.
> 
> makes sense, i will take this into the second patch.
> 
> I hope you can agree my thoughts about not mixing these 2 parts :)
> 
> regards Frank

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