31a171328e
This patch provides mostly a copy of serial8250_tx_dma() + __dma_tx_complete() with the following extensions: - DMA bug At least on AM335x the following problem exists: Even if the TX FIFO is empty and a TX transfer is programmed (and started) the UART does not trigger the DMA transfer. After $TRESHOLD number of bytes have been written to the FIFO manually the UART reevaluates the whole situation and decides that now there is enough room in the FIFO and so the transfer begins. This problem has not been seen on DRA7 or beagle board xm (OMAP3). I am not sure if this is UART-IP core specific or DMA engine. The workaround is to use a threshold of one byte, program the DMA transfer minus one byte and then to put the first byte into the FIFO to kick start the transfer. - support for runtime PM RPM is enabled on start_tx(). We can't disable RPM on DMA complete callback because there is still data in the FIFO which is being sent. We have to wait until the FIFO is empty before we disable it. For this to happen we fake a TX sent error and enable THRI. Once the FIFO is empty we receive an interrupt and since the TTY-buffer is still empty we "put RPM" via __stop_tx(). Should it been filed then in the start_tx() path we should program the DMA transfer and remove the error flag and the THRI bit. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| .. | ||
| asm-generic | ||
| drm | ||
| linux | ||
| misc | ||
| mtd | ||
| rdma | ||
| scsi | ||
| sound | ||
| video | ||
| xen | ||
| Kbuild | ||