Re: Driver mmap kernel memory

* Re: Driver mmap kernel memory
@ 2007-02-08  8:27 Micha Nelissen
  2007-02-08 11:45 ` Takashi Iwai
  0 siblings, 1 reply; 6+ messages in thread
From: Micha Nelissen @ 2007-02-08  8:27 UTC (permalink / raw)
  To: Takashi Iwai; +Cc: Alsa Development List

[-- Attachment #1: Type: text/plain, Size: 1111 bytes --]

Takashi Iwai wrote:
> At Wed, 7 Feb 2007 09:31:50 +0100,
> Micha Nelissen wrote:
>> 
>> The CPU architecture is armeb.
> 
> OK then you'd need dma_mmap_coherent() for mmapping the data.

Hmm? I'm not mmapping anything into user space, I suppose ALSA does this
?

In the driver, I access the buffer using the runtime->dma_area field.

>> I have more information now. The problem disappears if I do the
>> endian swap in the kernel driver. That means that I specify
>> SNDDRV_PCM_FMTBIT_S16_BE | SNDDRV_PCM_FMTBIT_S16_LE, instead of only
>> SNDDRV_PCM_FMTBIT_S16_BE, and I decide using the runtime->format
>> whether to swap or not.
> 
> Could you elaborate?  It sounds like a coincidence to me...

What do you want to know ? I've attached some code that shows the piece
in the kernel driver doing the checking of the buffer values
(alsa-buf-check.c). Also attached is an alsa test program that I used
(testtune.c).

Fields in my_device: p_start (= dma_area), p_cur (= current playback
pointer), p_end (= end of playback buffer); all point into dma_area.

Hope this helps,

Micha

[-- Attachment #2: alsa-buf-check.c --]
[-- Type: application/octet-stream, Size: 693 bytes --]

#if 1
				if (sample != my_device->exp_value) {
				    if (my_device->num_errors < 25) {
					int i;
					printk("error! expect=%d, got=%d, playpos=%d, wraps=%d, found @", 
					    my_device->exp_value, sample, 
					    (my_device->p_cur-my_device->playback_substream->runtime->dma_area)/sizeof(sample), 
					    my_device->num_wraps);
					for (i=0; i<32*1024; i++)
					    if (((s16*)my_device->playback_substream->runtime->dma_area)[i] == my_device->exp_value)
						printk(" %d", i);
					printk("\n");
				    } else if (my_device->num_errors == 25)
					printk("max number of sample errors reached\n");
				    my_device->num_errors++;
				}
				my_device->exp_value++;
#endif				

[-- Attachment #3: testtune.c --]
[-- Type: application/octet-stream, Size: 6997 bytes --]

#include <alsa/asoundlib.h>
#include <alsa/pcm.h>
#include <math.h>
#include <sys/time.h>

#define SWAP16(x) (((((unsigned short)x) & 0xff00) >> 8) | ((x & 0xff) << 8))

char* pcmdev = "default";

int main(int argc, char** argv)
{
        snd_pcm_hw_params_t *hwparams=NULL;
        snd_pcm_sw_params_t *swparams=NULL;
	snd_pcm_status_t* status;
	snd_pcm_t* pcm_handle;
        int dir;
        uint exact_uvalue;
        unsigned long exact_ulvalue;
	unsigned short* buf;
	struct timeval stv, ctv;
        int channels, sent, currtime, disptime, curravg, maxavg;
	int rate, format, stereo, rw, delay;
        int periods=2;
        int periodsize=500;
	int i, err, offset, numframes;

	rate = 8000;
	stereo = 0;
	rw = 1;

        if (snd_pcm_open(&pcm_handle, pcmdev, SND_PCM_STREAM_PLAYBACK,0) < 0) {
                printf("alsa_card_open_r: Error opening PCM device %s\n", pcmdev );
                return -1;
        }

        /* Allocate the snd_pcm_hw_params_t structure on the stack. */
        snd_pcm_hw_params_alloca(&hwparams);

        /* Init hwparams with full configuration space */
        if (snd_pcm_hw_params_any(pcm_handle, hwparams) < 0) {
                printf("alsa_set_params: Cannot configure this PCM device.\n");
                return -1;
        }

        if (snd_pcm_hw_params_set_access(pcm_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED) < 0) {
                printf("alsa_set_params: Error setting access.\n");
                return -1;
        }
        /* Set sample format */
        format=SND_PCM_FORMAT_S16_LE;
        if (snd_pcm_hw_params_set_format(pcm_handle, hwparams, format) < 0) {
                printf("alsa_set_params: Error setting format.\n");
                return -1;
        }
        /* Set number of channels */
        if (stereo) channels=2;
        else channels=1;
        if (snd_pcm_hw_params_set_channels(pcm_handle, hwparams, channels) < 0) {
                printf("alsa_set_params: Error setting channels.\n");
                return -1;
        }
        /* Set sample rate. If the exact rate is not supported */
        /* by the hardware, use nearest possible rate.         */
        exact_uvalue=rate;
        dir=0;
        if ((err=snd_pcm_hw_params_set_rate_near(pcm_handle, hwparams, &exact_uvalue, &dir))<0){
                printf("alsa_set_params: Error setting rate to %i:%s",rate,snd_strerror(err));
                return -1;
        }
        if (dir != 0) {
                printf("alsa_set_params: The rate %d Hz is not supported by your hardware.\n "
                "==> Using %d Hz instead.\n", rate, exact_uvalue);
        }
        /* choose greater period size when rate is high */
        periodsize=periodsize*(rate/8000);

        /* Set buffer size (in frames). The resulting latency is given by */
        /* latency = periodsize * periods / (rate * bytes_per_frame)     */
        /* set period size */
        exact_ulvalue=periodsize;
        dir=0;
        if (snd_pcm_hw_params_set_period_size_near(pcm_handle, hwparams, &exact_ulvalue, &dir) < 0) {
                printf("alsa_set_params: Error setting period size.\n");
                return -1;
        }
        if (dir != 0) {
                printf("alsa_set_params: The period size %d is not supported by your hardware.\n "
                "==> Using %d instead.\n", periodsize, (int)exact_ulvalue);
        }
        periodsize=exact_ulvalue;
        /* Set number of periods. Periods used to be called fragments. */
        exact_uvalue=periods;
        dir=0;
        if (snd_pcm_hw_params_set_periods_near(pcm_handle, hwparams, &exact_uvalue, &dir) < 0) {
                printf("alsa_set_params: Error setting periods.\n");
                return -1;
        }
        if (dir != 0) {
                printf("alsa_set_params: The number of periods %d is not supported by your hardware.\n "
                "==> Using %d instead.\n", periods, exact_uvalue);
        }
        /* Apply HW parameter settings to */
        /* PCM device and prepare device  */
        if ((err=snd_pcm_hw_params(pcm_handle, hwparams)) < 0) {
                printf("alsa_set_params: Error setting HW params:%s",snd_strerror(err));
                return -1;
        }
        /*prepare sw params */
        if (rw){
                snd_pcm_sw_params_alloca(&swparams);
                snd_pcm_sw_params_current(pcm_handle, swparams);
                if ((err=snd_pcm_sw_params_set_start_threshold(pcm_handle, swparams,periods*periodsize ))<0){
                        printf("alsa_set_params: Error setting start threshold:%s",snd_strerror(err));
                        return -1;
                }
                if ((err=snd_pcm_sw_params(pcm_handle, swparams))<0){
                        printf("alsa_set_params: Error setting SW params:%s",snd_strerror(err));
                        return -1;
                }
        }

	numframes = 64*1024;
	buf = malloc(numframes*sizeof(buf[0]));
	for (i = 0; i < numframes; i++){
		buf[i] = i;
		buf[i] = SWAP16(buf[i]);
	}

	gettimeofday(&stv, NULL);
	sent = 0;
	disptime = 0;
	maxavg = 0;
	offset = 0;
	snd_pcm_status_alloca(&status);
	do {
		err = snd_pcm_writei(pcm_handle, buf+offset, numframes-offset);
		//usleep(1000000);
		gettimeofday(&ctv, NULL);
		printf("T: %ld.%08ld bytes written=%3d ", 
		    ctv.tv_sec - stv.tv_sec - (ctv.tv_usec < stv.tv_usec ? 1 : 0), 
		    ctv.tv_usec - stv.tv_usec + (ctv.tv_usec < stv.tv_usec ? 1000000 : 0), err);
		if (err > 0) {
			sent += err;
			currtime = (ctv.tv_sec - stv.tv_sec);// * 1000 + (ctv.tv_usec - stv.tv_usec) / 1000;
			//if (ctv.tv_usec < stv.tv_usec)
			//	currtime += 1000;
			if (currtime > 0) {
				curravg = sent/currtime;
				if (curravg > maxavg)
					maxavg = curravg;
			}
			if (currtime > disptime) {
				//fprintf(stderr, "Playing rate: %5d samples/sec     \r", maxavg);
				disptime++;
				maxavg = 0;
			} 
		}
		if (err == -EAGAIN) {
			printf("overrun! waiting until buffer empty ");
			if (snd_pcm_wait(pcm_handle, 2000) == 0) {
			    printf("timed out! hw broken?\n");
			    break;
			}
		} else if (err == -EPIPE) {
			printf("underrun! ");
			snd_pcm_prepare(pcm_handle);
		} else if (err < 0) {
			printf("error %d: %s ", err, snd_strerror(err));
		} else if (err >= 0 && err < numframes) {
			offset += err;
		}
		if (snd_pcm_status(pcm_handle, status) < 0)
			printf("error getting status! ");
		delay = snd_pcm_status_get_delay(status);
		printf("delay=%4d ", delay);
		if (delay > 0 && delay < 640) {
			// speed up
			sent -= 320;
			printf("artificial speedup! ");
		}
		if (offset == numframes)
			offset = 0;
		ctv.tv_sec = stv.tv_sec + sent / rate - ctv.tv_sec;
		ctv.tv_usec = stv.tv_usec + (sent % rate) * 1000 / rate * 1000 - ctv.tv_usec;
		if (ctv.tv_usec < 0)
			ctv.tv_usec = 0;
		else if (ctv.tv_usec > 1000000) {
			ctv.tv_sec++;
			ctv.tv_usec -= 1000000;
		}
		printf("sleeping %ld.%06ld seconds\n", ctv.tv_sec, ctv.tv_usec);
		//select(0, NULL, NULL, NULL, &ctv);
	} while (1);

	return 0;
}

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