Anatolij Gustschin a646bd7f08 dma: ipu_idmac: do not lose valid received data in the irq handler ... Currently when two or more buffers are queued by the camera driver and so the double buffering is enabled in the idmac, we lose one frame comming from CSI since the reporting of arrival of the first frame is deferred by the DMAIC_7_EOF interrupt handler and reporting of the arrival of the last frame is not done at all. So when requesting N frames from the image sensor we actually receive N - 1 frames in user space. The reason for this behaviour is that the DMAIC_7_EOF interrupt handler misleadingly assumes that the CUR_BUF flag is pointing to the buffer used by the IDMAC. Actually it is not the case since the CUR_BUF flag will be flipped by the FSU when the FSU is sending the <TASK>_NEW_FRM_RDY signal when new frame data is delivered by the CSI. When sending this singal, FSU updates the DMA_CUR_BUF and the DMA_BUFx_RDY flags: the DMA_CUR_BUF is flipped, the DMA_BUFx_RDY is cleared, indicating that the frame data is beeing written by the IDMAC to the pointed buffer. DMA_BUFx_RDY is supposed to be set to the ready state again by the MCU, when it has handled the received data. DMAIC_7_CUR_BUF flag won't be flipped here by the IPU, so waiting for this event in the EOF interrupt handler is wrong. Actually there is no spurious interrupt as described in the comments, this is the valid DMAIC_7_EOF interrupt indicating reception of the frame from CSI. The patch removes code that waits for flipping of the DMAIC_7_CUR_BUF flag in the DMAIC_7_EOF interrupt handler. As the comment in the current code denotes, this waiting doesn't help anyway. As a result of this removal the reporting of the first arrived frame is not deferred to the time of arrival of the next frame and the drivers software flag 'ichan->active_buffer' is in sync with DMAIC_7_CUR_BUF flag, so the reception of all requested frames works. This has been verified on the hardware which is triggering the image sensor by the programmable state machine, allowing to obtain exact number of frames. On this hardware we do not tolerate losing frames. This patch also removes resetting the DMA_BUFx_RDY flags of all channels in ipu_disable_channel() since transfers on other DMA channels might be triggered by other running tasks and the buffers should always be ready for data sending or reception. Signed-off-by: Anatolij Gustschin <agust@denx.de> Reviewed-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Tested-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Dan Williams <dan.j.williams@intel.com>		2011-02-14 02:28:16 -08:00
..
ipu_idmac.c	dma: ipu_idmac: do not lose valid received data in the irq handler	2011-02-14 02:28:16 -08:00
ipu_intern.h
ipu_irq.c	dma: improve section assignment in i.MX31 IPU DMA driver	2009-03-25 09:13:24 -07:00
Makefile