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* 8250_dma.c - DMA Engine API support for 8250.c
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* Copyright (C) 2013 Intel Corporation
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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#include <linux/tty.h>
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#include <linux/tty_flip.h>
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#include <linux/serial_reg.h>
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#include <linux/dma-mapping.h>
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static void __dma_tx_complete(void *param)
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struct uart_8250_port *p = param;
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struct uart_8250_dma *dma = p->dma;
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struct circ_buf *xmit = &p->port.state->xmit;
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dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
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UART_XMIT_SIZE, DMA_TO_DEVICE);
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xmit->tail += dma->tx_size;
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xmit->tail &= UART_XMIT_SIZE - 1;
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p->port.icount.tx += dma->tx_size;
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if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
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uart_write_wakeup(&p->port);
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if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port))
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static void __dma_rx_complete(void *param)
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struct uart_8250_port *p = param;
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struct uart_8250_dma *dma = p->dma;
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struct tty_port *tty_port = &p->port.state->port;
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struct dma_tx_state state;
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dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,
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dma->rx_size, DMA_FROM_DEVICE);
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dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
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dmaengine_terminate_all(dma->rxchan);
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count = dma->rx_size - state.residue;
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tty_insert_flip_string(tty_port, dma->rx_buf, count);
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p->port.icount.rx += count;
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tty_flip_buffer_push(tty_port);
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int serial8250_tx_dma(struct uart_8250_port *p)
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struct uart_8250_dma *dma = p->dma;
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struct circ_buf *xmit = &p->port.state->xmit;
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struct dma_async_tx_descriptor *desc;
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if (uart_tx_stopped(&p->port) || dma->tx_running ||
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uart_circ_empty(xmit))
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dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
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desc = dmaengine_prep_slave_single(dma->txchan,
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dma->tx_addr + xmit->tail,
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dma->tx_size, DMA_MEM_TO_DEV,
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DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
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desc->callback = __dma_tx_complete;
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desc->callback_param = p;
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dma->tx_cookie = dmaengine_submit(desc);
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dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
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UART_XMIT_SIZE, DMA_TO_DEVICE);
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dma_async_issue_pending(dma->txchan);
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EXPORT_SYMBOL_GPL(serial8250_tx_dma);
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int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
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struct uart_8250_dma *dma = p->dma;
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struct dma_async_tx_descriptor *desc;
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struct dma_tx_state state;
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dma_status = dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
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switch (iir & 0x3f) {
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/* 8250_core handles errors and break interrupts */
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case UART_IIR_RX_TIMEOUT:
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* If RCVR FIFO trigger level was not reached, complete the
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* transfer and let 8250_core copy the remaining data.
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if (dma_status == DMA_IN_PROGRESS) {
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dmaengine_pause(dma->rxchan);
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__dma_rx_complete(p);
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desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
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dma->rx_size, DMA_DEV_TO_MEM,
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DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
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desc->callback = __dma_rx_complete;
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desc->callback_param = p;
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dma->rx_cookie = dmaengine_submit(desc);
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dma_sync_single_for_device(dma->rxchan->device->dev, dma->rx_addr,
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dma->rx_size, DMA_FROM_DEVICE);
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dma_async_issue_pending(dma->rxchan);
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EXPORT_SYMBOL_GPL(serial8250_rx_dma);
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int serial8250_request_dma(struct uart_8250_port *p)
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struct uart_8250_dma *dma = p->dma;
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/* Default slave configuration parameters */
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dma->rxconf.direction = DMA_DEV_TO_MEM;
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dma->rxconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
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dma->rxconf.src_addr = p->port.mapbase + UART_RX;
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dma->txconf.direction = DMA_MEM_TO_DEV;
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dma->txconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
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dma->txconf.dst_addr = p->port.mapbase + UART_TX;
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dma_cap_set(DMA_SLAVE, mask);
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/* Get a channel for RX */
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dma->rxchan = dma_request_slave_channel_compat(mask,
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dma->fn, dma->rx_param,
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dmaengine_slave_config(dma->rxchan, &dma->rxconf);
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/* Get a channel for TX */
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dma->txchan = dma_request_slave_channel_compat(mask,
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dma->fn, dma->tx_param,
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dma_release_channel(dma->rxchan);
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dmaengine_slave_config(dma->txchan, &dma->txconf);
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dma->rx_size = PAGE_SIZE;
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dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size,
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&dma->rx_addr, GFP_KERNEL);
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dma_release_channel(dma->rxchan);
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dma_release_channel(dma->txchan);
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dma->tx_addr = dma_map_single(dma->txchan->device->dev,
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p->port.state->xmit.buf,
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dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");
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EXPORT_SYMBOL_GPL(serial8250_request_dma);
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void serial8250_release_dma(struct uart_8250_port *p)
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struct uart_8250_dma *dma = p->dma;
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/* Release RX resources */
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dmaengine_terminate_all(dma->rxchan);
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dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf,
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dma_release_channel(dma->rxchan);
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/* Release TX resources */
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dmaengine_terminate_all(dma->txchan);
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dma_unmap_single(dma->txchan->device->dev, dma->tx_addr,
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UART_XMIT_SIZE, DMA_TO_DEVICE);
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dma_release_channel(dma->txchan);
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dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
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EXPORT_SYMBOL_GPL(serial8250_release_dma);