[linux-cirrus] Re: 2.6.20-rcX kernel status


On Dec 22, 2006, at 10:04 AM, Cory T. Tusar wrote:

* dma

-Lennert have done a dma patch
-which drivers should use it, is addional work necessary
-how to use it ?
I2S would probably benefit. IIRC, the original Cirrus driver did use DMA for 
I2S, however there were DMA channel issues with underrun. (?)


* sound i2s

???
I've been working on this recently in conjunction with a new project. Given some of the requirements, it was easier for me to start from scratch in this instance than attempt to port the older Cirrus I2S driver. I would like to go back at some point and either a) forward port the older Cirrus driver, or b) 
use what I've started on as a basis for an ALSA driver going forward.

To do this right will probably require DMA, SSP, and FIQ support.


*ssp

never used
There're 2 (3?) different implementations currently. Would be nice if this was structured similarly to the I2C core, allowing for registration of devices 
using the core set of functionality.
I'm currently working slowly on a forward port of the cirrus i2s alsa driver, including cirrus' ssp driver. The latest cirrus changelog talks about some dma issues being fixed. I'm not sure if these fix the underrun issues, but hopefully they do: 

2006-11-02 04:04  bbian

        Changed:
dev/linux-2.6.8.1/sound/arm/ep93xx-alsa-pcm.c (1.8), "Exp", lines: +158 -276 

        Fixed bug# 37318, DMA  error messages come out when use madplay
        with ac97 driver.  Merged the fix (Buffer management.) from I2S
        driver into AC97 driver.

2006-11-02 00:58  bbian

        Changed:
                dev/linux-2.6.8.1/sound/arm/ep93xx-i2s.c (1.16), "Exp", lines: 
+5 -5

        Fixed bug# 37315, "Segmentation fault" come out when test i2s audio
        driver.  Increased DMA buffer, adjusted the period size and amount.
Let me know if I should be going about this another way before I get in too deep. 

Thanks,
Chase Douglas

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