Re: [PATCH 1/4] i2c: imx: check busy bit when START/STOP

Richard Zhao
2009-10-02T08:17:09Z

On Fri, Oct 2, 2009 at 3:26 PM, Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> wrote:
> On Fri, Oct 02, 2009 at 08:57:04AM +0800, Richard Zhao wrote:
>> On Fri, Oct 2, 2009 at 12:37 AM, Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> wrote:
>> >> > Ah, so 'make the driver work on i.MX51' is a good statement which should
>> >> > be part of the commit message.
>> >> Well, maybe I can mention it.
>> >> But I think the good point is to present what you modified, not the side effect.
>> >
>> > It is not the side effect but the intention :) As no code is changed without a
>> > need, the reason really should be in the patch description.
>> No, it's not intention. I'm just trying to make the controller work in
>> a right way. Without this patch, maybe some other fast cpus have
>> problem too. I just tested mx31 and mx51. I will add "Without this
>> patch, i2c on some fast SoCs (for example imx51) will not work". Is it
>> ok for you?
>
> Please remember that we do not have i.MX51 support in mainline, so this
> is irrelevant atm.
So I don't need to meantion mx51? "Without this patch, i2c on some
fast SoCs will not work" is all right?
>
>> >
>> >> Yes. But I don't have multi-master system. So I can't say that.
>> >> The code is just taken from Freescale latest code. Without it, It
>> >> could also cause a device error. I forget the details.  Anyway, it
>> >> doesn't make anything wrong.
>> >
>> > Do you know where the details are explained?
>> No, I don't. I don't have device in hand now. If you have, could you
>> please help do a simple test?
>> Use hw to simulate multi-master system. Before execute xfer, you first
>> pull down SDA, then pull down SDC. It simulates a START. and execute
>> xfer to see whether IBB is set?
>
> No, we won't do any tests on hardware.
>
> At the moment we have a driver which is not multi master capable.
> Looking at the datasheet the change you do seems not enough to change
> this. So we should take a patch which changes something from which you
> think it might be needed? And you don't even have the details at hand?
>
> No.
Ok, It seems I have no reason to keep the busy wait before START.
Wolfram, do you agree to remove the busy wait? I saw you submmited the
original driver.
Let get away from multi-master. There's nearly no multi-master i2c bus
system in reality.

Thanks
Richard
>
> Sascha
>
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