From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Hofman Subject: Re: MIDI on ice1724 - real-time kernel problem Date: Wed, 30 Apr 2008 22:07:42 +0200 Message-ID: <4818D18E.5040409@insite.cz> References: <480E495B.20607@insite.cz> <480F189A.7030500@insite.cz> <480F99B8.3010408@insite.cz> <4810F1FA.4020300@insite.cz> <481182EB.1010800@insite.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mailserver.bobrnet.net (bobrnet.cust.inethome.cz [88.146.180.6]) by alsa0.perex.cz (Postfix) with ESMTP id 0D0F32476F for ; Wed, 30 Apr 2008 22:07:49 +0200 (CEST) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Takashi Iwai Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org Takashi Iwai wrote: > At Fri, 25 Apr 2008 09:06:19 +0200, > Pavel Hofman wrote: >> Takashi Iwai wrote: >>>> I do not know the reason for MPU401_INFO_NO_ACK. You removed it from the >>>> original patch, but without it I always get the input/output error. >>> Ah, thanks, I overlooked it. >>> Fixed now. >> Takashi, thanks, but the patch I sent you sets MPU401_INFO_INPUT and >> MPU401_INFO_OUTPUT flags too. They enable the actual input/output >> methods in mpu401_uart.c. > > They aren't needed if you create full-duplex streams. > Could you check whether the latest code still causes any errors? 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. 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. My HW: ancient AMD Duron 900MHz. The interrupt flood occurs no matter whether the MIDI input is connected to my MIDI keyboard or not. Thanks a lot to anyone for suggestions. Pavel.