> -----Original Message----- > From: linux-tegra-ow...@vger.kernel.org <linux-tegra- > ow...@vger.kernel.org> On Behalf Of Thierry Reding > Sent: Tuesday, August 13, 2019 3:12 PM > To: Krishna Yarlagadda <kyarlaga...@nvidia.com> > Cc: gre...@linuxfoundation.org; robh...@kernel.org; > mark.rutl...@arm.com; Jonathan Hunter <jonath...@nvidia.com>; Laxman > Dewangan <ldewan...@nvidia.com>; jsl...@suse.com; linux- > ser...@vger.kernel.org; devicet...@vger.kernel.org; linux- > te...@vger.kernel.org; linux-kernel@vger.kernel.org; Shardar Mohammed > <smoham...@nvidia.com> > Subject: Re: [PATCH 02/14] serial: tegra: add support to ignore read > > On Mon, Aug 12, 2019 at 04:58:11PM +0530, Krishna Yarlagadda wrote: > > From: Shardar Shariff Md <smoham...@nvidia.com> > > > > Add support to ignore read characters if CREAD flag is not set. > > > > Signed-off-by: Shardar Shariff Md <smoham...@nvidia.com> > > Signed-off-by: Krishna Yarlagadda <kyarlaga...@nvidia.com> > > --- > > drivers/tty/serial/serial-tegra.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/drivers/tty/serial/serial-tegra.c > > b/drivers/tty/serial/serial-tegra.c > > index 19f4c24..93d299e 100644 > > --- a/drivers/tty/serial/serial-tegra.c > > +++ b/drivers/tty/serial/serial-tegra.c > > @@ -542,6 +542,9 @@ static void tegra_uart_handle_rx_pio(struct > tegra_uart_port *tup, > > ch = (unsigned char) tegra_uart_read(tup, UART_RX); > > tup->uport.icount.rx++; > > > > + if (tup->uport.ignore_status_mask & UART_LSR_DR) > > + continue; > > + > > if (!uart_handle_sysrq_char(&tup->uport, ch) && tty) > > tty_insert_flip_char(tty, ch, flag); > > Is it a good idea to ignore even sysrq characters if CREAD is not set? > According to termios, CREAD enables the receiver, so technically if it isn't > set > you can't even receive sysrq characters. But I don't know if there are any > rules regarding this. > > Is this the same way that other drivers work? > > Thierry > Looked into few drivers and sysrq characters are not ignored. This driver does not support console driver. So this might not be needed.
KY > > } while (1); > > @@ -562,6 +565,10 @@ static void tegra_uart_copy_rx_to_tty(struct > tegra_uart_port *tup, > > dev_err(tup->uport.dev, "No tty port\n"); > > return; > > } > > + > > + if (tup->uport.ignore_status_mask & UART_LSR_DR) > > + return; > > + > > dma_sync_single_for_cpu(tup->uport.dev, tup->rx_dma_buf_phys, > > TEGRA_UART_RX_DMA_BUFFER_SIZE, > DMA_FROM_DEVICE); > > copied = tty_insert_flip_string(tty, @@ -1190,6 +1197,11 @@ static > > void tegra_uart_set_termios(struct uart_port *u, > > tegra_uart_write(tup, tup->ier_shadow, UART_IER); > > tegra_uart_read(tup, UART_IER); > > > > + tup->uport.ignore_status_mask = 0; > > + /* Ignore all characters if CREAD is not set */ > > + if ((termios->c_cflag & CREAD) == 0) > > + tup->uport.ignore_status_mask |= UART_LSR_DR; > > + > > spin_unlock_irqrestore(&u->lock, flags); } > > > > -- > > 2.7.4 > >
