forked from Minki/linux
05b2723387
Rework the way the DMA buffer is handled and IRQs are generated. ALSA uses a ring-buffer of multiple periods. Each period is supposed to corrispond to one IRQ. The existing driver was generating one interrupt per ring-buffer, as opposed to per period. This meant that as soon as the IRQ was generated, the hardware was already starting to re-write the beginning of the buffer. Since the DMA happens on a per-line basis, there was only a narrow window to copy the data out before the buffer was overwritten. The cx88 core RISC program generator is modified so that it can set the IRQ and counter flags to count every X lines of DMA transfer. This way we can generate an interrupt every period instead of every full ring-buffer. Right now only period of one line are supported, but it should be possible to support longer periods. Note that a WRITE instruction generates an IRQ when it starts, not when the transfer is finished. Thus to generate an IRQ when line X is done, one must set the IRQ flag on the instruction that starts line X+1, not the one that ends line X. Change the line size so that there are four lines in the SRAM FIFO. If there are not four lines, the analog output from the cx88's internal DACs is full of clicks and pops. Try to handle FIFO sync errors. Sometimes the chip generates many of these errors before audio data starts. Up to 50 sync errors will be ignored and the counter reset. Have the IRQ handler save the RISC counter to the chip struct, and then have the pointer callback use this to calculate the pointer position. We could read the counter from the pointer callback, but sometimes the sync errors on start up cause the counter to go crazy. ALSA sees this and thinks there has been an overrun. The IRQ hander can avoid saving the counter position on sync errors. The chip "opened" flag wasn't necessary. ALSA won't try to open the same substream multiple times. Probably this code was cut&pasted from the bt87x driver, which has multiple sub-streams for one chip. Do error checking for the videobuf mapping functions. snd_card_cx88_runtime_free() is useless and can be deleted. Signed-off-by: Trent Piepho <xyzzy@speakeasy.org> Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org> |
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| .. | ||
| cx88-alsa.c | ||
| cx88-blackbird.c | ||
| cx88-cards.c | ||
| cx88-core.c | ||
| cx88-dvb.c | ||
| cx88-i2c.c | ||
| cx88-input.c | ||
| cx88-mpeg.c | ||
| cx88-reg.h | ||
| cx88-tvaudio.c | ||
| cx88-vbi.c | ||
| cx88-video.c | ||
| cx88-vp3054-i2c.c | ||
| cx88-vp3054-i2c.h | ||
| cx88.h | ||
| Kconfig | ||
| Makefile | ||