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From: Vignesh R <vigneshr@ti.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	<linux-serial@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<linux-omap@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	Vignesh R <vigneshr@ti.com>
Subject: [PATCH 1/2] serial: 8250: Don't service RX FIFO if interrupts are disabled
Date: Thu, 8 Feb 2018 18:25:41 +0530	[thread overview]
Message-ID: <20180208125542.15649-2-vigneshr@ti.com> (raw)
In-Reply-To: <20180208125542.15649-1-vigneshr@ti.com>

Currently, data in RX FIFO is read based on UART_LSR register state even
if RDI and RLSI interrupts are disabled in UART_IER register.
This is because when IRQ handler is called due to TX FIFO empty event,
RX FIFO is serviced based on UART_LSR register status instead of
UART_IIR status. This defeats the purpose of disabling UART RX
FIFO interrupts during throttling(see, omap_8250_throttle()) as IRQ
handler continues to drain UART RX FIFO resulting in overflow of buffer
at tty layer.
Fix this by making sure that driver drains UART RX FIFO only when
UART_IIR_RDI is set along with UART_LSR_BI or UART_LSR_DR bits.

Signed-off-by: Vignesh R <vigneshr@ti.com>
---
 drivers/tty/serial/8250/8250_port.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 1328c7e70108..ffbb955d1c06 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1854,7 +1854,8 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 
 	status = serial_port_in(port, UART_LSR);
 
-	if (status & (UART_LSR_DR | UART_LSR_BI)) {
+	if (status & (UART_LSR_DR | UART_LSR_BI) &&
+	    iir & UART_IIR_RDI) {
 		if (!up->dma || handle_rx_dma(up, iir))
 			status = serial8250_rx_chars(up, status);
 	}
-- 
2.16.1


WARNING: multiple messages have this Message-ID (diff)
From: Vignesh R <vigneshr@ti.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Vignesh R <vigneshr@ti.com>,
	linux-kernel@vger.kernel.org,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	linux-serial@vger.kernel.org, Jiri Slaby <jslaby@suse.com>,
	linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] serial: 8250: Don't service RX FIFO if interrupts are disabled
Date: Thu, 8 Feb 2018 18:25:41 +0530	[thread overview]
Message-ID: <20180208125542.15649-2-vigneshr@ti.com> (raw)
In-Reply-To: <20180208125542.15649-1-vigneshr@ti.com>

Currently, data in RX FIFO is read based on UART_LSR register state even
if RDI and RLSI interrupts are disabled in UART_IER register.
This is because when IRQ handler is called due to TX FIFO empty event,
RX FIFO is serviced based on UART_LSR register status instead of
UART_IIR status. This defeats the purpose of disabling UART RX
FIFO interrupts during throttling(see, omap_8250_throttle()) as IRQ
handler continues to drain UART RX FIFO resulting in overflow of buffer
at tty layer.
Fix this by making sure that driver drains UART RX FIFO only when
UART_IIR_RDI is set along with UART_LSR_BI or UART_LSR_DR bits.

Signed-off-by: Vignesh R <vigneshr@ti.com>
---
 drivers/tty/serial/8250/8250_port.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 1328c7e70108..ffbb955d1c06 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1854,7 +1854,8 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 
 	status = serial_port_in(port, UART_LSR);
 
-	if (status & (UART_LSR_DR | UART_LSR_BI)) {
+	if (status & (UART_LSR_DR | UART_LSR_BI) &&
+	    iir & UART_IIR_RDI) {
 		if (!up->dma || handle_rx_dma(up, iir))
 			status = serial8250_rx_chars(up, status);
 	}
-- 
2.16.1

WARNING: multiple messages have this Message-ID (diff)
From: vigneshr@ti.com (Vignesh R)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] serial: 8250: Don't service RX FIFO if interrupts are disabled
Date: Thu, 8 Feb 2018 18:25:41 +0530	[thread overview]
Message-ID: <20180208125542.15649-2-vigneshr@ti.com> (raw)
In-Reply-To: <20180208125542.15649-1-vigneshr@ti.com>

Currently, data in RX FIFO is read based on UART_LSR register state even
if RDI and RLSI interrupts are disabled in UART_IER register.
This is because when IRQ handler is called due to TX FIFO empty event,
RX FIFO is serviced based on UART_LSR register status instead of
UART_IIR status. This defeats the purpose of disabling UART RX
FIFO interrupts during throttling(see, omap_8250_throttle()) as IRQ
handler continues to drain UART RX FIFO resulting in overflow of buffer
at tty layer.
Fix this by making sure that driver drains UART RX FIFO only when
UART_IIR_RDI is set along with UART_LSR_BI or UART_LSR_DR bits.

Signed-off-by: Vignesh R <vigneshr@ti.com>
---
 drivers/tty/serial/8250/8250_port.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 1328c7e70108..ffbb955d1c06 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1854,7 +1854,8 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 
 	status = serial_port_in(port, UART_LSR);
 
-	if (status & (UART_LSR_DR | UART_LSR_BI)) {
+	if (status & (UART_LSR_DR | UART_LSR_BI) &&
+	    iir & UART_IIR_RDI) {
 		if (!up->dma || handle_rx_dma(up, iir))
 			status = serial8250_rx_chars(up, status);
 	}
-- 
2.16.1

  reply	other threads:[~2018-02-08 12:55 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-08 12:55 [PATCH 0/2] 8250_omap: Fix issues with throttling of 8250 port Vignesh R
2018-02-08 12:55 ` Vignesh R
2018-02-08 12:55 ` Vignesh R
2018-02-08 12:55 ` Vignesh R [this message]
2018-02-08 12:55   ` [PATCH 1/2] serial: 8250: Don't service RX FIFO if interrupts are disabled Vignesh R
2018-02-08 12:55   ` Vignesh R
2018-02-08 15:16   ` Andy Shevchenko
2018-02-08 15:16     ` Andy Shevchenko
2018-02-08 17:15     ` Vignesh R
2018-02-08 17:15       ` Vignesh R
2018-02-08 17:15       ` Vignesh R
2018-02-08 12:55 ` [PATCH 2/2] serial: 8250: 8250_omap: Fix throttling when DMA is enabled Vignesh R
2018-02-08 12:55   ` Vignesh R
2018-02-08 12:55   ` Vignesh R

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