Takashi Iwai wrote:
At Sat, 03 May 2008 21:12:02 +0200, Pavel Hofman wrote:
Takashi Iwai wrote:
At Wed, 30 Apr 2008 22:07:42 +0200, Pavel Hofman wrote:
Takashi Iwai wrote:
At Fri, 25 Apr 2008 09:06:19 +0200, Pavel Hofman wrote:
The code works fine on standard kernel.
But in the RT kernel of Ubuntu 7.10 (2.6.22-14-rt, 1000HZ compared to 250HZ of the -generic kernel), MIDI interrupts get thrown continuously, hogging CPU with the IRQXX "process".
When playing 44.1kHz audio with buffer size of 32768, snd_vt1724_interrupt is called every 185ms. With the buffer size of 4096, it is every 23ms. So far so good.
But when I try to output some midi, the routine gets called every 24us (i.e. 1000 times faster). Comparing the time difference between my several debug printk's in snd_vt1724_interrupt (approx. 5us between each printk record a few lines of code apart) and between each call of the method (24us), I thought there would be a loop somewhere in the interrupt handler calling code. But /proc/interrupts really shows over 40k interrupts a second for ICE1724.
Changing the watermarks up to 0x1f makes no difference.
That looks bad.
Masking the MIDI interrupts works, snd_vt1724_interrupt is called only during VT1724_IRQ_MTPCM interrupts, with the MIDI status bits MPU_TX/MPU_RX set when reading/writing with amidi.
Hm, is it TX or RX, or in both cases? Could you check which one (TX or RX) causes this?
Both reading (amidi -p hw:0 -d) and writing (amidi -p hw:0 -S F0411042110C000000000074FF0411042110C000000) starts the TX interrupt flood (irq status: 0x20) immediately. Upon opening input as well as output the method snd_mpu401_do_reset is called - is perhaps the culprit somewhere there?
Possibly. It write 0x00 to data at the beginning in snd_mpu401_uart_cmd(). What happens if you remove it?
Unfortunately nothing, no change.
Actually, when does the MPU_TX interrupt get thrown? Upon exhausting some output buffer? I understand interrupts for DMA, but mpu uart does not use DMA, right?
Thanks a lot for help, I am not giving up :)
Pavel.