8 Jan
2008
8 Jan
'08
9:39 a.m.
At Mon, 07 Jan 2008 23:23:02 -0800, Tobin Davis wrote:
On Tue, 2008-01-08 at 08:11 +0100, Takashi Iwai wrote:
At Mon, 07 Jan 2008 10:00:20 -0800, Tobin Davis wrote: > > On Mon, 2008-01-07 at 11:59 +0100, Takashi Iwai wrote: > > At Thu, 03 Jan 2008 15:34:05 -0800, > Tobin Davis wrote: > > > > Summary: hda_intel.c use gcap register to determine number of streams > > supported by southbridge. > > > > This patch removes hardcoded values for the number of streams supported > > by the southbridge in most chipsets, and reads these values from the > > chipset directly. Most systems are hardwired for 4 streams in each > > direction, but newer chipsets change that capability. > > > > > > Signed off by Tobin Davis <tdavis@dsl-only.net> > > [2 hda-gcap.patch <text/x-patch; UTF-8 (7bit)>] > > diff -r 1227a1c12325 pci/hda/hda_intel.c > > --- a/pci/hda/hda_intel.c Mon Dec 24 14:40:56 2007 +0100 > > +++ b/pci/hda/hda_intel.c Thu Jan 03 15:27:10 2008 -0800 > > @@ -1709,12 +1709,13 @@ static int __devinit azx_create(struct s > > { > > struct azx *chip; > > int err; > > + unsigned short gcap; > > static struct snd_device_ops ops = { > > .dev_free = azx_dev_free, > > }; > > > > *rchip = NULL; > > - > > + > > err = pci_enable_device(pci); > > if (err < 0) > > return err; > > @@ -1790,10 +1791,19 @@ static int __devinit azx_create(struct s > > chip->capture_index_offset = ATIHDMI_CAPTURE_INDEX; > > break; > > default: > > - chip->playback_streams = ICH6_NUM_PLAYBACK; > > - chip->capture_streams = ICH6_NUM_CAPTURE; > > - chip->playback_index_offset = ICH6_PLAYBACK_INDEX; > > - chip->capture_index_offset = ICH6_CAPTURE_INDEX; > > + /* read number of streams from GCAP register instead of using > > + * hardcoded value > > + */ > > + gcap = azx_readw(chip, GCAP); > > + if(!gcap) { > > + snd_printk(KERN_ERR "Device has no streams \n"); > > + goto errout; > > + }; > > I think it's safer to assign old ICH6_* values in this case (just to > be sure) after a warning message. > > Actually, this should never have been hardcoded in the first place. The HDA > PRM (April 2005) states that the value returned is hardwired to 4 streams in > the ICH6/7 southbridge of the Intel chipset. By hardcoding the values in the > driver, we don't allow changes to future (hint - real soon) chipsets. This > just cleans up this bit of code that has been around since this code was > created. If I had the other systems in the case statement to test, I'm sure > we could do away with the case statement entirely, just by reading the values > instead of second guessing them. If the chipsets follow the spec, this method > should work all around. Well, I wasn't clear about the comment above. I meant the constant values can be used as fallbacks in case these values can't be read, instead of returning error and quit. This would avoid regressions, at least. > > + chip->playback_streams = (gcap&(0xF<<12))>>12; > > + chip->capture_streams = (gcap&(0xF<<8))>>8; > > + chip->playback_index_offset = (gcap&(0xF<<12))>>12; > > + chip->capture_index_offset = 0; > > I'm not entirely convinced of this method for the index_offsets, but it works > on tested systems here. I'll review the PRM for more guidance. It should be fine as is. A stream can be assigned freely regardless the I/O direction on ICH (and others too). So, basically it's always: capture_index_offset = 0; playback_index_offset = capture_streams;This isn't entirely true, at least based on the ATIHDMI code in the previous case statement.
ATIHDMI has no capture. Thus the above is OK.
It would be interesting to see what GCAP returns for the two cases (ATIHDMI, and ULI). If they could be used by this, we could do away with the switch entirely (except maybe as a fallback).
Yes, but it's not so important at this stage unless they release new (incompatible) hardwares.
Takashi