[PATCH 5/5] atmel_serial: Add DMA support
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From: Haavard Skinnemoen on 18 Dec 2007 12:10 From: Chip Coldwell <hskinnemoen(a)atmel.com> This patch is based on the DMA-patch by Chip Coldwell for the AT91/AT32 serial USARTS, with some tweaks to make it apply neatly on top of the other patches in this series. The RX code has been moved to a tasklet and reworked a bit. Instead of depending on the ENDRX and TIMEOUT bits in CSR, we simply grab as much data as we can from the DMA buffers. I think this closes a race where the ENDRX bit is set after we read CSR but before we read RPR, although I haven't confirmed this. This also fixes a DMA sync bug in the original patch. [linux(a)bohmer.net: rebased onto irq-splitup patch] [hskinnemoen(a)atmel.com: moved to tasklet, fixed dma bug, misc cleanups] Signed-off-by: Remy Bohmer <linux(a)bohmer.net> Signed-off-by: Haavard Skinnemoen <hskinnemoen(a)atmel.com> --- drivers/serial/atmel_serial.c | 386 ++++++++++++++++++++++++++++++++++++++-- 1 files changed, 366 insertions(+), 20 deletions(-) diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c index 990d3ab..07c2734 100644 --- a/drivers/serial/atmel_serial.c +++ b/drivers/serial/atmel_serial.c @@ -7,6 +7,8 @@ * Based on drivers/char/serial_sa1100.c, by Deep Blue Solutions Ltd. * Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o. * + * DMA support added by Chip Coldwell. + * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or @@ -33,6 +35,7 @@ #include <linux/sysrq.h> #include <linux/tty_flip.h> #include <linux/platform_device.h> +#include <linux/dma-mapping.h> #include <linux/atmel_pdc.h> #include <asm/io.h> @@ -47,6 +50,11 @@ #include "atmel_serial.h" +#define SUPPORT_PDC +#define PDC_BUFFER_SIZE (L1_CACHE_BYTES << 3) +#warning "Revisit" +#define PDC_RX_TIMEOUT (3 * 10) /* 3 bytes */ + #if defined(CONFIG_SERIAL_ATMEL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ) #define SUPPORT_SYSRQ #endif @@ -111,6 +119,13 @@ static int (*atmel_open_hook) (struct uart_port *); static void (*atmel_close_hook) (struct uart_port *); +struct atmel_dma_buffer { + unsigned char *buf; + dma_addr_t dma_addr; + size_t dma_size; + unsigned int ofs; +}; + struct atmel_uart_char { u16 status; u16 ch; @@ -127,6 +142,13 @@ struct atmel_uart_port { unsigned short suspended; /* is port suspended? */ int break_active; /* break being received */ + short use_dma_rx; /* enable PDC receiver */ + short pdc_rx_idx; /* current PDC RX buffer */ + struct atmel_dma_buffer pdc_rx[2]; /* PDC receier */ + + short use_dma_tx; /* enable PDC transmitter */ + struct atmel_dma_buffer pdc_tx; /* PDC transmitter */ + struct tasklet_struct tasklet; unsigned int irq_pending; unsigned int irq_status; @@ -136,10 +158,39 @@ struct atmel_uart_port { static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART]; +#define PDC_RX_BUF(port) &(port)->pdc_rx[(port)->pdc_rx_idx] +#define PDC_RX_SWITCH(port) (port)->pdc_rx_idx = !(port)->pdc_rx_idx + #ifdef SUPPORT_SYSRQ static struct console atmel_console; #endif +#ifdef SUPPORT_PDC +static bool atmel_use_dma_rx(struct uart_port *port) +{ + struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port; + + return atmel_port->use_dma_rx; +} + +static bool atmel_use_dma_tx(struct uart_port *port) +{ + struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port; + + return atmel_port->use_dma_tx; +} +#else +static bool atmel_use_dma_rx(struct uart_port *port) +{ + return false; +} + +static bool atmel_use_dma_tx(struct uart_port *port) +{ + return false; +} +#endif + /* * Return TIOCSER_TEMT when transmitter FIFO and Shift register is empty. */ @@ -221,7 +272,12 @@ static u_int atmel_get_mctrl(struct uart_port *port) */ static void atmel_stop_tx(struct uart_port *port) { - UART_PUT_IDR(port, ATMEL_US_TXRDY); + if (atmel_use_dma_tx(port)) { + /* disable PDC transmit */ + UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS); + UART_PUT_IDR(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE); + } else + UART_PUT_IDR(port, ATMEL_US_TXRDY); } /* @@ -229,7 +285,17 @@ static void atmel_stop_tx(struct uart_port *port) */ static void atmel_start_tx(struct uart_port *port) { - UART_PUT_IER(port, ATMEL_US_TXRDY); + if (atmel_use_dma_tx(port)) { + if (UART_GET_PTSR(port) & ATMEL_PDC_TXTEN) + /* The transmitter is already running. Yes, we + really need this.*/ + return; + + UART_PUT_IER(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE); + /* re-enable PDC transmit */ + UART_PUT_PTCR(port, ATMEL_PDC_TXTEN); + } else + UART_PUT_IER(port, ATMEL_US_TXRDY); } /* @@ -237,7 +303,12 @@ static void atmel_start_tx(struct uart_port *port) */ static void atmel_stop_rx(struct uart_port *port) { - UART_PUT_IDR(port, ATMEL_US_RXRDY); + if (atmel_use_dma_rx(port)) { + /* disable PDC receive */ + UART_PUT_PTCR(port, ATMEL_PDC_RXTDIS); + UART_PUT_IDR(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT); + } else + UART_PUT_IDR(port, ATMEL_US_RXRDY); } /* @@ -286,6 +357,87 @@ atmel_buffer_rx_char(struct uart_port *port, unsigned int status, } /* + * Deal with parity, framing and overrun errors. + */ +static void atmel_pdc_rxerr(struct uart_port *port, unsigned int status) +{ + /* clear error */ + UART_PUT_CR(port, ATMEL_US_RSTSTA); + + if (status & ATMEL_US_RXBRK) { + /* ignore side-effect */ + status &= ~(ATMEL_US_PARE | ATMEL_US_FRAME); + port->icount.brk++; + } + if (status & ATMEL_US_PARE) + port->icount.parity++; + if (status & ATMEL_US_FRAME) + port->icount.frame++; + if (status & ATMEL_US_OVRE) + port->icount.overrun++; +} + +/* + * A transmission via the PDC is complete. + */ +static void atmel_pdc_endtx(struct uart_port *port) +{ + struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port; + struct circ_buf *xmit = &port->info->xmit; + struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx; + + xmit->tail += pdc->ofs; + if (xmit->tail >= SERIAL_XMIT_SIZE) + xmit->tail -= SERIAL_XMIT_SIZE; + + port->icount.tx += pdc->ofs; + pdc->ofs = 0; + + if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) + uart_write_wakeup(port); +} + +/* + * The PDC transmitter is idle, so either start the next transfer or + * disable the transmitter. + */ +static void atmel_pdc_txbufe(struct uart_port *port) +{ + struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port; + struct circ_buf *xmit = &port->info->xmit; + struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx; + int count; + + if (!uart_circ_empty(xmit)) { + /* more to transmit - setup next transfer */ + + /* disable PDC transmit */ + UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS); + dma_sync_single_for_device(port->dev, + pdc->dma_addr, + pdc->dma_size, + DMA_TO_DEVICE); + + if (xmit->tail < xmit->head) + count = xmit->head - xmit->tail; + else + count = SERIAL_XMIT_SIZE - xmit->tail; + pdc->ofs = count; + + UART_PUT_TPR(port, pdc->dma_addr + xmit->tail); + UART_PUT_TCR(port, count); + /* re-enable PDC transmit */ + UART_PUT_PTCR(port, ATMEL_PDC_TXTEN); + } else { + /* nothing left to transmit - disable the transmitter */ + + /* disable PDC transmit */ + UART_PUT_PTCR(port, ATMEL_PDC_TXTDIS); + UART_PUT_IDR(port, ATMEL_US_ENDTX | ATMEL_US_TXBUFE); + } +} + +/* * Characters received (called from interrupt handler) */ static void atmel_rx_chars(struct uart_port *port) @@ -374,6 +526,25 @@ atmel_handle_receive(struct uart_port *port, unsigned int pending) { struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port; + if (atmel_use_dma_rx(port)) { + /* + * PDC receive. Just schedule the tasklet and let it + * figure out the details. + * + * TODO: We're not handling error flags correctly at + * the moment. + */ + if (pending & (ATMEL_US_ENDRX | ATMEL_US_TIMEOUT)) { + UART_PUT_IDR(port, (ATMEL_US_ENDRX + | ATMEL_US_TIMEOUT)); + tasklet_schedule(&atmel_port->tasklet); + } + + if (pending & (ATMEL_US_RXBRK | ATMEL_US_OVRE | + ATMEL_US_FRAME | ATMEL_US_PARE)) + atmel_pdc_rxerr(port, pending); + } + /* Interrupt receive */ if (pending & ATMEL_US_RXRDY) atmel_rx_chars(port); @@ -394,6 +565,12 @@ atmel_handle_receive(struct uart_port *port, unsigned int pending) static void atmel_handle_transmit(struct uart_port *port, unsigned int pending) { + /* PDC transmit */ + if (pending & ATMEL_US_ENDTX) + atmel_pdc_endtx(port); + if (pending & ATMEL_US_TXBUFE) + atmel_pdc_txbufe(port); + /* Interrupt transmit */ if (pending & ATMEL_US_TXRDY) atmel_tx_chars(port); @@ -426,19 +603,17 @@ static irqreturn_t atmel_interrupt(int irq, void *dev_id) struct uart_port *port = dev_id; unsigned int status, pending, pass_counter = 0; - status = UART_GET_CSR(port); - pending = status & UART_GET_IMR(port); - while (pending) { + do { + status = UART_GET_CSR(port); + pending = status & UART_GET_IMR(port); + if (!pending) + break; + atmel_handle_receive(port, pending); atmel_handle_status(port, pending, status); atmel_handle_transmit(port, pending); + } while (pass_counter++ < ATMEL_ISR_PASS_LIMIT); - if (pass_counter++ > ATMEL_ISR_PASS_LIMIT) - break; - - status = UART_GET_CSR(port); - pending = status & UART_GET_IMR(port); - } return IRQ_HANDLED; } @@ -504,6 +679,70 @@ static void atmel_rx_from_ring(struct uart_port *port) tty_flip_buffer_push(port->info->tty); } +static void atmel_rx_from_dma(struct uart_port *port) +{ + struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port; + struct tty_struct *tty = port->info->tty; + struct atmel_dma_buffer *pdc; + int rx_idx = atmel_port->pdc_rx_idx; + unsigned int head; + unsigned int tail; + unsigned int count; + + do { + /* Reset the UART timeout early so that we don't miss one */ + UART_PUT_CR(port, ATMEL_US_STTTO); + + pdc = &atmel_port->pdc_rx[rx_idx]; + head = UART_GET_RPR(port) - pdc->dma_addr; + tail = pdc->ofs; + + /* If the PDC has switched buffers, RPR won't contain + * any address within the current buffer. Since head + * is unsigned, we just need a one-way comparison to + * find out. + * + * In this case, we just need to consume the entire + * buffer and resubmit it for DMA. This will clear the + * ENDRX bit as well, so that we can safely re-enable + * all interrupts below. + */ + if (head >= pdc->dma_size) + head = pdc->dma_size; + + if (likely(head != tail)) { + dma_sync_single_for_cpu(port->dev, pdc->dma_addr, + pdc->dma_size, DMA_FROM_DEVICE); + + count = head - tail; + tty_insert_flip_string(tty, pdc->buf + pdc->ofs, count); + + dma_sync_single_for_device(port->dev, pdc->dma_addr, + pdc->dma_size, DMA_FROM_DEVICE); + + port->icount.rx += count; + pdc->ofs = head; + } + + /* + * If the current buffer is full, we need to check if + * the next one contains any additional data. + */ + if (head >= pdc->dma_size) { + pdc->ofs = 0; + UART_PUT_RNPR(port, pdc->dma_addr); + UART_PUT_RNCR(port, pdc->dma_size); + + rx_idx = !rx_idx; + atmel_port->pdc_rx_idx = rx_idx; + } + } while (head >= pdc->dma_size); + + tty_flip_buffer_push(tty); + + UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT); +} + /* * tasklet handling tty stuff outside the interrupt handler. */ @@ -540,7 +779,10 @@ static void atmel_tasklet_func(unsigned long data) spin_unlock_irqrestore(&port->lock, flags); } - atmel_rx_from_ring(port); + if (atmel_use_dma_rx(port)) + atmel_rx_from_dma(port); + else + atmel_rx_from_ring(port); } /* @@ -548,6 +790,7 @@ static void atmel_tasklet_func(unsigned long data) */ static int atmel_startup(struct uart_port *port) { + struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port; int retval; /* @@ -568,6 +811,56 @@ static int atmel_startup(struct uart_port *port) } /* + * Initialize DMA (if necessary) + */ + if (atmel_use_dma_rx(port)) { + int i; + + for (i = 0; i < 2; i++) { + struct atmel_dma_buffer *pdc = &atmel_port->pdc_rx[i]; + + pdc->buf = kmalloc(PDC_BUFFER_SIZE, GFP_KERNEL); + if (pdc->buf == NULL) { + if (i != 0) { + dma_unmap_single(port->dev, + atmel_port->pdc_rx[0].dma_addr, + PDC_BUFFER_SIZE, + DMA_FROM_DEVICE); + kfree(atmel_port->pdc_rx[0].buf); + } + free_irq(port->irq, port); + return -ENOMEM; + } + pdc->dma_addr = dma_map_single(port->dev, + pdc->buf, + PDC_BUFFER_SIZE, + DMA_FROM_DEVICE); + pdc->dma_size = PDC_BUFFER_SIZE; + pdc->ofs = 0; + } + + atmel_port->pdc_rx_idx = 0; + + UART_PUT_RPR(port, atmel_port->pdc_rx[0].dma_addr); + UART_PUT_RCR(port, PDC_BUFFER_SIZE); + + UART_PUT_RNPR(port, atmel_port->pdc_rx[1].dma_addr); + UART_PUT_RNCR(port, PDC_BUFFER_SIZE); + } + if (atmel_use_dma_tx(port)) { + struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx; + struct circ_buf *xmit = &port->info->xmit; + + pdc->buf = xmit->buf; + pdc->dma_addr = dma_map_single(port->dev, + pdc->buf, + SERIAL_XMIT_SIZE, + DMA_TO_DEVICE); + pdc->dma_size = SERIAL_XMIT_SIZE; + pdc->ofs = 0; + } + + /* * If there is a specific "open" function (to register * control line interrupts) */ @@ -586,8 +879,18 @@ static int atmel_startup(struct uart_port *port) /* enable xmit & rcvr */ UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN); - /* enable receive only */ - UART_PUT_IER(port, ATMEL_US_RXRDY); + if (atmel_use_dma_rx(port)) { + /* set UART timeout */ + UART_PUT_RTOR(port, PDC_RX_TIMEOUT); + UART_PUT_CR(port, ATMEL_US_STTTO); + + UART_PUT_IER(port, ATMEL_US_ENDRX | ATMEL_US_TIMEOUT); + /* enable PDC controller */ + UART_PUT_PTCR(port, ATMEL_PDC_RXTEN); + } else { + /* enable receive only */ + UART_PUT_IER(port, ATMEL_US_RXRDY); + } return 0; } @@ -597,6 +900,38 @@ static int atmel_startup(struct uart_port *port) */ static void atmel_shutdown(struct uart_port *port) { + struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port; + /* + * Ensure everything is stopped. + */ + atmel_stop_rx(port); + atmel_stop_tx(port); + + /* + * Shut-down the DMA. + */ + if (atmel_use_dma_rx(port)) { + int i; + + for (i = 0; i < 2; i++) { + struct atmel_dma_buffer *pdc = &atmel_port->pdc_rx[i]; + + dma_unmap_single(port->dev, + pdc->dma_addr, + pdc->dma_size, + DMA_FROM_DEVICE); + kfree(pdc->buf); + } + } + if (atmel_use_dma_tx(port)) { + struct atmel_dma_buffer *pdc = &atmel_port->pdc_tx; + + dma_unmap_single(port->dev, + pdc->dma_addr, + pdc->dma_size, + DMA_TO_DEVICE); + } + /* * Disable all interrupts, port and break condition. */ @@ -708,6 +1043,10 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios, if (termios->c_iflag & (BRKINT | PARMRK)) port->read_status_mask |= ATMEL_US_RXBRK; + if (atmel_use_dma_rx(port)) + /* need to enable error interrupts */ + UART_PUT_IER(port, port->read_status_mask); + /* * Characters to ignore */ @@ -893,6 +1232,11 @@ static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port, clk_enable(atmel_port->clk); port->uartclk = clk_get_rate(atmel_port->clk); } + + atmel_port->use_dma_rx = data->use_dma_rx; + atmel_port->use_dma_tx = data->use_dma_tx; + if (atmel_use_dma_tx(port)) + port->fifosize = PDC_BUFFER_SIZE; } /* @@ -1077,7 +1421,7 @@ static int atmel_serial_suspend(struct platform_device *pdev, struct atmel_uart_port *atmel_port = (struct atmel_uart_port *)port; if (device_may_wakeup(&pdev->dev) - && !at91_suspend_entering_slow_clock()) + && !clk_must_disable(atmel_port->clk)) enable_irq_wake(port->irq); else { uart_suspend_port(&atmel_uart, port); @@ -1116,10 +1460,12 @@ static int __devinit atmel_serial_probe(struct platform_device *pdev) port = &atmel_ports[pdev->id]; atmel_init_port(port, pdev); - data = kmalloc(ATMEL_SERIAL_RINGSIZE, GFP_KERNEL); - if (!data) - return -ENOMEM; - port->rx_ring.buf = data; + if (!atmel_use_dma_rx(&port->uart)) { + data = kmalloc(ATMEL_SERIAL_RINGSIZE, GFP_KERNEL); + if (!data) + return -ENOMEM; + port->rx_ring.buf = data; + } ret = uart_add_one_port(&atmel_uart, &port->uart); if (!ret) { -- 1.5.3.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |