| Message ID | 1410377411-26656-14-git-send-email-bigeasy@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Sep 10, 2014 at 09:30:08PM +0200, Sebastian Andrzej Siewior wrote: > There is nothing to do for RPM in the RX path. If the HW goes off then it > won't assert the DMA line and the transfer won't happen. So we hope that > the HW does not go off for RX to work (DMA or PIO makes no difference > here). > > For TX the situation is slightly different. 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. That last sentence starts out a bit messy. > > Reviewed-by: Tony Lindgren <tony@atomide.com> > Tested-by: Tony Lindgren <tony@atomide.com> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > --- > drivers/tty/serial/8250/8250_dma.c | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c > index 898a6781d0b3..e8850219b150 100644 > --- a/drivers/tty/serial/8250/8250_dma.c > +++ b/drivers/tty/serial/8250/8250_dma.c > @@ -21,6 +21,7 @@ static void __dma_tx_complete(void *param) > struct uart_8250_dma *dma = p->dma; > struct circ_buf *xmit = &p->port.state->xmit; > unsigned long flags; > + bool en_thri = false; > > dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr, > UART_XMIT_SIZE, DMA_TO_DEVICE); > @@ -40,11 +41,16 @@ static void __dma_tx_complete(void *param) > int ret; > > ret = serial8250_tx_dma(p); > - if (ret) { > - dma->tx_err = 1; > - p->ier |= UART_IER_THRI; > - serial_port_out(&p->port, UART_IER, p->ier); > - } > + if (ret) > + en_thri = true; > + > + } else if (p->capabilities & UART_CAP_RPM) > + en_thri = true; > + > + if (en_thri) { > + dma->tx_err = 1; > + p->ier |= UART_IER_THRI; > + serial_port_out(&p->port, UART_IER, p->ier); > } > > spin_unlock_irqrestore(&p->port.lock, flags); > -- > 2.1.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
* Frans Klaver | 2014-09-29 11:26:06 [+0200]: >On Wed, Sep 10, 2014 at 09:30:08PM +0200, Sebastian Andrzej Siewior wrote: >> There is nothing to do for RPM in the RX path. If the HW goes off then it >> won't assert the DMA line and the transfer won't happen. So we hope that >> the HW does not go off for RX to work (DMA or PIO makes no difference >> here). >> >> For TX the situation is slightly different. 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. > >That last sentence starts out a bit messy. This got mered so there is nothing I can do about it anymore. But I will try to fix comments in code where and in patches that are not yet merged (what you report :)) Sebastian
diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c index 898a6781d0b3..e8850219b150 100644 --- a/drivers/tty/serial/8250/8250_dma.c +++ b/drivers/tty/serial/8250/8250_dma.c @@ -21,6 +21,7 @@ static void __dma_tx_complete(void *param) struct uart_8250_dma *dma = p->dma; struct circ_buf *xmit = &p->port.state->xmit; unsigned long flags; + bool en_thri = false; dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr, UART_XMIT_SIZE, DMA_TO_DEVICE); @@ -40,11 +41,16 @@ static void __dma_tx_complete(void *param) int ret; ret = serial8250_tx_dma(p); - if (ret) { - dma->tx_err = 1; - p->ier |= UART_IER_THRI; - serial_port_out(&p->port, UART_IER, p->ier); - } + if (ret) + en_thri = true; + + } else if (p->capabilities & UART_CAP_RPM) + en_thri = true; + + if (en_thri) { + dma->tx_err = 1; + p->ier |= UART_IER_THRI; + serial_port_out(&p->port, UART_IER, p->ier); } spin_unlock_irqrestore(&p->port.lock, flags);