linux-kernel - Re: [PATCH] ASoC: fsl_sai: Add isr to deal with error flag

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Message-ID: <20140327035726.GA16359@MrMyself>
Date:	Thu, 27 Mar 2014 11:57:27 +0800
From:	Nicolin Chen <Guangyu.Chen@...escale.com>
To:	Xiubo Li-B47053 <Li.Xiubo@...escale.com>
CC:	"broonie@...nel.org" <broonie@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>
Subject: Re: [PATCH] ASoC: fsl_sai: Add isr to deal with error flag

On Thu, Mar 27, 2014 at 12:06:53PM +0800, Xiubo Li-B47053 wrote:
> > > > > > > > +	if (xcsr & FSL_SAI_CSR_FWF)
> > > > > > > > +		dev_dbg(dev, "isr: Enabled transmit FIFO is empty\n");
> > > > > > > > +
> > > > > > > > +	if (xcsr & FSL_SAI_CSR_FRF)
> > > > > > > > +		dev_dbg(dev, "isr: Transmit FIFO watermark has been
> > > > reached\n");
> > > > > > > > +
> > > > > > >
> > > > > > > While are these ones really needed to clear manually ?
> > > > > >
> > > > > > The reference manual doesn't mention about the requirement. So SAI
> > should
> > > > do
> > > > > > the self-clearance.
> > > > >
> > > > > Yes, I do think we should let it do the self-clearance, and shouldn't
> > > > interfere
> > > > > of them...
> > > >
> > > > SAI is supposed to ignore the interference, isn't it?
> > > >
> > >
> > > Maybe, but I'm not very sure.
> > > And these bits are all writable and readable.
> > 
> > Double-confirmed? Because FWF and FRF should be read-only bits.
> > 
> 
> So let's just ignore the clearance of these bits in isr().
> 
> +++++
> SAI Transmit Control Register (I2S1_TCSR) : 32 : R/W : 0000_0000h

I'm talking about FWF and FRF bits, not TCSR as a register.

> -----
> 
> I have checked in the Vybrid and LS1 SoC datasheets, and they are all the
> Same as above, and nothing else.
> 
> Have I missed ?

What i.MX IC team told me is SAI ignores what we do to FWF and FRF, so you
don't need to worry about it at all unless Vybrid makes them writable, in
which case we may also need to clear these bits and confirm with Vybrid IC
team if they're also W1C.


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