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From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Codrin.Ciubotariu@microchip.com
Cc: wsa@kernel.org, linux-i2c@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, robh+dt@kernel.org,
	Ludovic.Desroches@microchip.com, Nicolas.Ferre@microchip.com,
	alexandre.belloni@bootlin.com, kamel.bouhara@bootlin.com
Subject: Re: [RFC PATCH 1/4] dt-binding: i2c: add generic properties for GPIO bus recovery
Date: Mon, 27 Jul 2020 11:50:29 +0100
Message-ID: <20200727105029.GI1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <b3a04528-0053-16bf-f092-147685298ced@microchip.com>

On Mon, Jul 27, 2020 at 10:44:57AM +0000, Codrin.Ciubotariu@microchip.com wrote:
> On 24.07.2020 23:52, Russell King - ARM Linux admin wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > On Fri, Jul 24, 2020 at 09:39:13PM +0200, Wolfram Sang wrote:
> >> On Sun, Jul 05, 2020 at 11:19:18PM +0200, Wolfram Sang wrote:
> >>>
> >>>> +- pinctrl
> >>>> + add extra pinctrl to configure SCL/SDA pins to GPIO function for bus
> >>>> + recovery, call it "gpio" or "recovery" state
> >>>
> >>> I think we should stick with "gpio" only. That is what at91 and imx have
> >>> in their bindings. pxa uses "recovery" as a pinctrl state name but I
> >>> can't find any further use or documentation of that. PXA is not fully
> >>> converted to the best of my knowledge, so maybe it is no problem for PXA
> >>> to switch to "gpio", too? We should ask Russell King (cced).
> > 
> > Fully converted to what?  The generic handling where the i2c core layer
> > handles everything to do with recovery, including the switch between
> > modes?
> > 
> > i2c-pxa _intentionally_ carefully handles the switch between i2c mode and
> > GPIO mode, and I don't see a generic driver doing that to avoid causing
> > any additional glitches on the bus.  Given the use case that this recovery
> > is targetted at, avoiding glitches is very important to keep.
> 
> Why is it not possbile to handle glitches in a generic way? I guess it 
> depends on the pinctl, but we could treat a worst-case scenario to 
> assure the switch between states is done properly.

Please look at how i2c-pxa switches between the two, and decide whether
the generic implementation can do the same.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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  reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-19 14:19 [RFC PATCH 0/4] i2c: core: add generic " Codrin Ciubotariu
2020-06-19 14:19 ` [RFC PATCH 1/4] dt-binding: i2c: add generic properties for " Codrin Ciubotariu
2020-07-05 21:19   ` Wolfram Sang
2020-07-24 19:39     ` Wolfram Sang
2020-07-24 20:52       ` Russell King - ARM Linux admin
2020-07-27 10:44         ` Codrin.Ciubotariu
2020-07-27 10:50           ` Russell King - ARM Linux admin [this message]
2020-07-30  9:00             ` Codrin.Ciubotariu
2020-08-03 14:16               ` Russell King - ARM Linux admin
2020-08-03 16:42                 ` Codrin.Ciubotariu
2020-07-15 19:21   ` Rob Herring
2020-06-19 14:19 ` [RFC PATCH 2/4] i2c: core: add generic I2C GPIO recovery Codrin Ciubotariu
2020-08-02 16:54   ` Wolfram Sang
2020-08-03 13:27     ` Codrin.Ciubotariu
2020-08-03 16:49       ` wsa
2020-06-19 14:19 ` [RFC PATCH 3/4] i2c: core: treat EPROBE_DEFER when acquiring SCL/SDA GPIOs Codrin Ciubotariu
2020-08-02 17:05   ` Wolfram Sang
2020-08-03 15:33     ` Codrin.Ciubotariu
2020-08-03 16:59       ` wsa
2020-06-19 14:19 ` [RFC PATCH 4/4] i2c: at91: Move to generic GPIO bus recovery Codrin Ciubotariu
2020-08-02 17:08   ` Wolfram Sang
2020-08-03 15:42     ` Codrin.Ciubotariu
2020-08-03 16:59       ` wsa
2020-08-26  6:14       ` Wolfram Sang
2020-09-04  8:55         ` Codrin.Ciubotariu
2020-09-04  9:20           ` Wolfram Sang
2020-07-05 21:09 ` [RFC PATCH 0/4] i2c: core: add " Wolfram Sang

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