Hi, I have been working on developing alsa driver for wm8974 codec on i.mx27 platform. The wm8974 codec is connected to i.mx27 via SSI1 port. And the OS kernel is linux-2.6.19.2.By now, the driver modules can be successfully built and installed/loaded into kernel. I tested the driver playback function with a wav file (8KHz, 16-bit, mono) recorded by Audacity on my laptop.The playback of this wave file on my laptop lasts about 51 seconds. But when I play it (via aplay) on the mx27 platform, the playback time lasts about 34 seconds, and the playback speed is quite faster than the normal speed and the speaker output sounds like being compressed. In my driver, wm8974 works in I2S master mode and mx27 ssi1 is configured as I2S slave. The configuration of wm9874 audio interface register is 0x10, which set wm8974 as I2S master, word length is 16bits, normal bclk and frame clock polarity. The configuration of mx27 ssi1 transmission channel is as follows(using ssi api from kernel 2.6.19.2): ssi_tx_shift_direction(ssi, 0); // MSB first shift ssi_tx_clock_polarity(ssi, 0); // clock on RISING edge ssi_tx_frame_sync_active(ssi, 1);// frame sync LOW active ssi_tx_early_frame_sync(ssi, 1);//init frame sync one bit before data ssi_tx_frame_sync_length(ssi, 0); //one word length frame ssi_tx_bit0(ssi, 1); // shifting w.r.t. bit 0 of TXSR ssi_tx_word_length(ssi, 0x7); //16bit WL ssi_tx_frame_rate(ssi, 2); // DC[4:0] non-zero ssi_tx_clock_direction(ssi, 0); // external bit clock ssi_tx_frame_direction(ssi, 0); // external frame sync ssi_tx_clock_divide_by_two(ssi, 0); ssi_tx_clock_prescaler(ssi, 0); ssi_tx_fifo_empty_watermark(ssi, 0, TX_WATERMARK);//TX_WATERMARK=4 ssi_tx_fifo_enable(ssi, 0, 1); // tx fifo0 enable ssi_transmit_enable(ssi, 1); // transmit section enable ssi_interrupt_enable(ssi, ssi_tx_dma_interrupt_enable); // enable tx dma ssi_interrupt_enable(ssi, ssi_tx_fifo_0_empty); ssi_interrupt_enable(ssi, ssi_tx_fifo_1_empty); ssi_i2s_mode(ssi, 2); //i2s slave Here I'm not very sure about the setting of frame rate and frame sync length. Is the above setting right? But even I set frame rate to 1, it does not make any difference. What's the possible reason causing the incorrect faster playback speed? Any suggestion is appreciated. Regards, Jie Jiang _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
