From mboxrd@z Thu Jan  1 00:00:00 1970
From: Grygorii Strashko <grygorii.strashko-l0cyMroinI0@public.gmane.org>
Subject: Re: [5/5] i2c: davinci: use ICPFUNC to toggle I2C as gpio for bus
 recovery
Date: Mon, 24 Nov 2014 21:22:24 +0200
Message-ID: <54738570.8070601@ti.com>
References: <1416477788-5544-6-git-send-email-grygorii.strashko@ti.com> <20141123170400.GC4431@pengutronix.de> <54732F8E.4080105@ti.com> <54737532.1050808@milosoftware.com>
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To: Mike Looijmans <info-KQxf8TFvCoAi8rCdYzckzA@public.gmane.org>, =?windows-1252?Q?Uwe_Kleine?= =?windows-1252?Q?-K=F6nig?= <u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
Cc: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Sekhar Nori <nsekhar-l0cyMroinI0@public.gmane.org>, Kevin Hilman <khilman-1D3HCaltpLuhEniVeURVKkEOCMrvLtNR@public.gmane.org>, Santosh Shilimkar <ssantosh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Murali Karicheri <m-karicheri2-l0cyMroinI0@public.gmane.org>, Ben Gardiner <bengardiner-ScDXFp4xN3PN+rMO2ozGnw@public.gmane.org>, Mike Looijmans <milo-software-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
List-Id: linux-i2c@vger.kernel.org

On 11/24/2014 08:13 PM, Mike Looijmans wrote:
> On 24-11-2014 14:15, Grygorii Strashko wrote:
>> Hi Uwe,
>> On 11/23/2014 07:04 PM, Uwe Kleine-K=F6nig wrote:
>>> On Thu, Nov 20, 2014 at 12:03:08PM +0200, Grygorii Strashko wrote:
>>>> @@ -664,6 +759,7 @@ static int davinci_i2c_probe(struct=20
>>>> platform_device *pdev)
>>>>            if (!of_property_read_u32(pdev->dev.of_node,=20
>>>> "clock-frequency",
>>>>                &prop))
>>>>                dev->pdata->bus_freq =3D prop / 1000;
>>>> +        dev->pdata->has_pfunc =3D true;
>>> I don't understand this. Why does this ICPFUNC recovery work if the=
 bus
>>> is probed by oftree, but doesn't if not?
>> I've mentioned this in commit message:
>>   Allow platforms to indicate the presence of the ICPFUNC registers=20
>> with a has_pfunc
>>   platform data flag and enable this mode for platforms which suppor=
ts=20
>> DT (da850 and
>>   Keystone 2 are two SoCs which support DT now and they also support=
=20
>> ICPFUNC registers).
>>
>> I'll add proper comment here.
>=20
> Just thinking: What happens if you try to use the ICPFUNC registers o=
n=20
> platforms that don't support it? If the answer is "nothing bad", then=
=20
> you might as well assume that if the platform doesn't specify its own=
=20
> GPIOs, you can always try using the ICPFUNC registers to shake the I2=
C=20
> bus. Better to try and fail than to never try at all...
>=20

I think the right answer is !"nothing bad".

My intention was to enable this feature by default, because current DT-=
compatible
SoCs support it and the possibility that older SoCs will migrate to DT =
is low.
But now I think that the right way will be to add proper compatible str=
ings
and use them to detect if ICPFUNC registers are supported or not.

[...]

regards,
-grygorii