linux-kernel - Re: [SPAM] [PATCH v2 04/11] i2c: nomadik: simplify IRQ masking logic

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Message-Id: <CZKVC09R7VQB.3DEDAIWIICORV@bootlin.com>
Date: Mon, 04 Mar 2024 10:46:26 +0100
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Andi Shyti" <andi.shyti@...nel.org>
Cc: "Linus Walleij" <linus.walleij@...aro.org>, "Rob Herring"
 <robh+dt@...nel.org>, "Krzysztof Kozlowski"
 <krzysztof.kozlowski+dt@...aro.org>, "Conor Dooley" <conor+dt@...nel.org>,
 "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
 <linux-arm-kernel@...ts.infradead.org>, <linux-i2c@...r.kernel.org>,
 <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
 <linux-mips@...r.kernel.org>, "Gregory Clement"
 <gregory.clement@...tlin.com>, "Vladimir Kondratiev"
 <vladimir.kondratiev@...ileye.com>, "Thomas Petazzoni"
 <thomas.petazzoni@...tlin.com>, "Tawfik Bayouk"
 <tawfik.bayouk@...ileye.com>
Subject: Re: [SPAM] [PATCH v2 04/11] i2c: nomadik: simplify IRQ masking
 logic

Hello,

On Sat Mar 2, 2024 at 1:39 AM CET, Andi Shyti wrote:
> On Thu, Feb 29, 2024 at 07:10:52PM +0100, Théo Lebrun wrote:
> > IRQ_MASK and I2C_CLEAR_ALL_INTS are redundant. One masks the top three
>
> if I2C_CLEAR_ALL_INTS is redundant why don't you remove it?

I understand this is unclear. What I meant by redundant is that they are
redundant from one another; one overlaps the other. I'll give a better
commit description for v3. Something like:

   IRQ_MASK and I2C_CLEAR_ALL_INTS both mask available interrupts.
   IRQ_MASK removes top options (bits 29-31). I2C_CLEAR_ALL_INTS
   removes reserved options including top bits. Keep the latter.

   31  29  27  25  23  21  19  17  15  13  11  09  07  05  03  01
     30  28  26  24  22  20  18  16  14  12  10  08  06  04  02  00
   --- IRQ_MASK: --------------------------------------------------
          1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
    0 0 0
   --- I2C_CLEAR_ALL_INTS: ----------------------------------------
          1     1 1       1 1 1 1 1                   1 1 1 1 1 1 1
    0 0 0   0 0     0 0 0           0 0 0 0 0 0 0 0 0

    Notice I2C_CLEAR_ALL_INTS is more restrictive than IRQ_MASK.

Is that better?

> > bits off as reserved, the other one masks the reserved IRQs inside the
> > u32. Get rid of IRQ_MASK and only use the most restrictive mask.
>
> Why is IRQ_MASK redundant? What happens if you write in the
> reserved bits?

The wording wasn't correct. Have I answered your
question from the above?

Thanks Andi,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com