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From: Maxime Ripard <mripard@kernel.org>
To: Corentin Labbe <clabbe.montjoie@gmail.com>
Cc: mark.rutland@arm.com, devicetree@vger.kernel.org,
	herbert@gondor.apana.org.au, linux-sunxi@googlegroups.com,
	linux@armlinux.org.uk, linux-kernel@vger.kernel.org,
	wens@csie.org, robh+dt@kernel.org, linux-crypto@vger.kernel.org,
	davem@davemloft.net, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/9] crypto: Add Allwinner sun8i-ce Crypto Engine
Date: Mon, 9 Sep 2019 15:59:10 +0200
Message-ID: <20190909135908.vkvcuykrplhxxwtd@flea> (raw)
In-Reply-To: <20190909131906.GA12882@Red>

On Mon, Sep 09, 2019 at 03:19:06PM +0200, Corentin Labbe wrote:
> On Mon, Sep 09, 2019 at 01:38:37PM +0200, Maxime Ripard wrote:
> > On Sat, Sep 07, 2019 at 09:04:08PM +0200, Corentin Labbe wrote:
> > > > Also, I'm not sure what is the point of having the clocks names be
> > > > parameters there as well. It's constant across all the compatibles,
> > > > the only thing that isn't is the number of clocks and the module clock
> > > > rate. It's what you should have in there.
> > >
> > > Since the datasheet give some max frequency, I think I will add a
> > > max_freq and add a check to verify if the clock is in the right
> > > range
> >
> > It's a bit pointless. What are you going to do if it's not correct?
> > What are you trying to fix / report with this?
>
> I thinked to print a warning.  If someone want to play with
> overclocking for example, the driver should said that probably some
> result could be invalid.

If someone wants to play with overclocking, the crypto engine is going
to be the least of their concern.

> > > > > +int sun8i_ce_get_engine_number(struct sun8i_ce_dev *ce)
> > > > > +{
> > > > > +	return atomic_inc_return(&ce->flow) % ce->variant->maxflow;
> > > > > +}
> > > >
> > > > I'm not sure what this is supposed to be doing, but that mod there
> > > > seems pretty dangerous.
> > > >
> > > > ...
> > >
> > > This mod do a round robin on each channel.
> > > I dont see why it is dangerous.
> >
> > Well, you're using the atomic API here which is most commonly used for
> > refcounting, while you're using a mod.
> >
> > Plus, while the increment is atomic, the modulo isn't, so you can end
> > up in a case where you would be preempted between the
> > atomic_inc_return and the mod, which is dangerous.
> >
> > Again, I'm not sure what this function is doing (which is also a
> > problem in itself). I guess you should just make it clearer what it
> > does, and then we can discuss it properly.
>
> Each request need to be assigned to a channel.
> Each channel are identified by a number from 1 to 4.
>
> So this function return the channel to use, 1 then 2 then 3 then 4 then 1...
>
> Note that this is uncritical. If, due to anything, two request are
> assigned to the same channel, nothing will break.

I'm not sure why you're using the atomic API then?

Also, I guess a bitfield and find_first_bit (and a different function
name) would be more obvious to the reader.

Thanks!
Maxime

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Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-06 18:45 [PATCH 0/9] crypto: add sun8i-ce driver for Allwinner crypto engine Corentin Labbe
2019-09-06 18:45 ` [PATCH 1/9] crypto: Add allwinner subdirectory Corentin Labbe
2019-09-07  3:54   ` Maxime Ripard
2019-09-07 17:53     ` Corentin Labbe
2019-09-06 18:45 ` [PATCH 2/9] crypto: Add Allwinner sun8i-ce Crypto Engine Corentin Labbe
2019-09-07  8:19   ` Maxime Ripard
2019-09-07 19:04     ` Corentin Labbe
2019-09-09 11:38       ` Maxime Ripard
2019-09-09 13:19         ` Corentin Labbe
2019-09-09 13:59           ` Maxime Ripard [this message]
2019-09-06 18:45 ` [PATCH 3/9] dt-bindings: crypto: Add DT bindings documentation for " Corentin Labbe
2019-09-07  4:01   ` Maxime Ripard
2019-09-11 18:31     ` Corentin Labbe
2019-09-12  9:37       ` Maxime Ripard
2019-09-12 20:26         ` Chen-Yu Tsai
2019-09-12 20:33           ` Maxime Ripard
2019-09-12 20:37             ` Chen-Yu Tsai
2019-09-13 12:11               ` Maxime Ripard
2019-09-06 18:45 ` [PATCH 4/9] ARM: dts: sun8i: r40: add crypto engine node Corentin Labbe
2019-09-07  4:02   ` Maxime Ripard
2019-09-07 17:54     ` Corentin Labbe
2019-09-06 18:45 ` [PATCH 5/9] ARM: dts: sun8i: h3: Add Crypto Engine node Corentin Labbe
2019-09-06 18:45 ` [PATCH 6/9] ARM64: dts: allwinner: sun50i: Add Crypto Engine node on A64 Corentin Labbe
2019-09-07  4:02   ` Maxime Ripard
2019-09-07 17:54     ` Corentin Labbe
2019-09-06 18:45 ` [PATCH 7/9] ARM64: dts: allwinner: sun50i: Add crypto engine node on H5 Corentin Labbe
2019-09-06 18:45 ` [PATCH 8/9] ARM64: dts: allwinner: sun50i: Add Crypto Engine node on H6 Corentin Labbe
2019-09-06 18:45 ` [PATCH 9/9] sunxi_defconfig: add new crypto options Corentin Labbe
2019-09-07  4:03   ` Maxime Ripard
2019-09-07 17:55     ` Corentin Labbe
2019-09-13  8:15     ` Corentin Labbe
2019-09-13 12:10       ` Maxime Ripard

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