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b=gfV2hkVCiDICWcBNi22TuccdKVIYin7mVx06JCkyIeFC1QWu88pmtm485qK64T6ao FF1rDTD6ErkqCFYE9yKo0ybuggN1hvTqCAr4grYINKqdpllzJX6ipHpBVURNZngDUJ 3PeU4OrBeearV212XGw4HuUmfLleYlPCgOn8/yFNlxVJwBFblumiFkmjuGbecTMgno FbupFmKd5EucCMzbSOLwxXczleV1xaCZqgfv1jZbn7RH91RgbjRyLDwPHm+BR+4VMB fNBSwEIEStUWwKHMQ3DFsupeoDuhI22QN74U8ZNCxxWFOEOGQTvzsslSb08l8xGyTd CWhKUelf+sd+A== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: linux-tegra-owner@vger.kernel.org owner@vger.kernel.org> On Behalf Of Thierry Reding > Sent: Tuesday, August 13, 2019 3:12 PM > To: Krishna Yarlagadda > Cc: gregkh@linuxfoundation.org; robh+dt@kernel.org; > mark.rutland@arm.com; Jonathan Hunter ; Laxman > Dewangan ; jslaby@suse.com; linux- > serial@vger.kernel.org; devicetree@vger.kernel.org; linux- > tegra@vger.kernel.org; linux-kernel@vger.kernel.org; Shardar Mohammed > > Subject: Re: [PATCH 02/14] serial: tegra: add support to ignore read >=20 > On Mon, Aug 12, 2019 at 04:58:11PM +0530, Krishna Yarlagadda wrote: > > From: Shardar Shariff Md > > > > Add support to ignore read characters if CREAD flag is not set. > > > > Signed-off-by: Shardar Shariff Md > > Signed-off-by: Krishna Yarlagadda > > --- > > 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 =3D (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); >=20 > 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 is= n't set > you can't even receive sysrq characters. But I don't know if there are an= y > rules regarding this. >=20 > Is this the same way that other drivers work? >=20 > Thierry >=20 Looked into few drivers and sysrq characters are not ignored. This driver d= oes 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 =3D 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 =3D 0; > > + /* Ignore all characters if CREAD is not set */ > > + if ((termios->c_cflag & CREAD) =3D=3D 0) > > + tup->uport.ignore_status_mask |=3D UART_LSR_DR; > > + > > spin_unlock_irqrestore(&u->lock, flags); } > > > > -- > > 2.7.4 > >