Re: [PATCH 5/7] ASoC: tegra: add ac97 host driver

[Lucas Stach <dev-8ppwABl0HbeELgA04lAiVw@public.gmane.org>]

Am Donnerstag, den 20.12.2012, 13:19 -0700 schrieb Stephen Warren:
> On 12/20/2012 01:10 PM, Lucas Stach wrote:
> > Am Donnerstag, den 20.12.2012, 12:44 -0700 schrieb Stephen Warren:
> >> On 12/19/2012 04:17 PM, Lucas Stach wrote:
> >>> This adds the driver for the Tegra 2x AC97 host controller.
> 
> >>> +static void tegra20_ac97_codec_warm_reset(struct snd_ac97 *ac97)
> >>> +{
> >>> +	u32 readback;
> >>> +	unsigned long timeout;
> >>> +
> >>> +	/*
> >>> +	 * although sync line is driven by the DAC pad group warm reset using
> >>> +	 * the controller cmd is not working, have to toggle sync line
> >>> +	 * manually.
> >>> +	 */
> >>> +	gpio_request(workdata->sync_gpio, "codec-sync");
> >>
> >> Hmm. There's an AC'97 command to reset the CODEC and we don't implement
> >> it? Uggh.
> >
> > As far as I could figure from the downstream register doc there is a
> > command implemented in the host controller that's supposed to do the
> > warm reset, but in my testing it didn't work. Sadly I have not received
> > any documentation about the host controller from NVIDIA up until now, so
> > I don't now if we could make this work somehow. Bug Submission ID#:
> > 196075
> 
> What system was that bug submitted into? It's not a regular NVIDIA
> internal bug number. I'll see who I can ask about this feature...
> 
Submitted through the Tegra Registered Developer Program webpage. I got
a reply from someone saying they are looking if they can get anything
out, but haven't heard back until now.

> >>> +	ac97->sync_gpio = of_get_named_gpio(pdev->dev.of_node,
> >>> +					    "nvidia,codec-sync-gpio", 0);
> >>> +	if (!gpio_is_valid(ac97->sync_gpio)) {
> >>> +		dev_err(&pdev->dev, "no codec-sync GPIO supplied\n");
> >>> +		goto err_clk_put;
> >>> +	}
> >>
> >> I don't know what this is, so I'll ask if it's strictly required too.
> >
> > Until we manage to get the host controller warm reset command working
> > this is fixed to be the _FS line of the DAP connected to the codec, so
> > strictly required.
> 
> I'd like to investigate whether the warm reset command can be made to
> work before actually committing to a DT binding that requires this GPIO
> to be specified; the DT binding is supposed to be basically static.
> 
Ok with me. We still have plenty of time left for the 3.9 merge window
and that's what I'm targeting with those patches.