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From: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
To: linux-renesas-soc@vger.kernel.org, wsa@the-dreams.de,
	geert@linux-m68k.org
Cc: linux-serial@vger.kernel.org, magnus.damm@gmail.com,
	Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Subject: [PATCH 2/7] serial: sh-sci: consider DR (data ready) bit adequately
Date: Fri,  9 Dec 2016 13:36:06 +0100	[thread overview]
Message-ID: <1481286971-16667-3-git-send-email-ulrich.hecht+renesas@gmail.com> (raw)
In-Reply-To: <1481286971-16667-1-git-send-email-ulrich.hecht+renesas@gmail.com>

To allow operation with a higher RX FIFO interrupt threshold in PIO
mode, it is necessary to consider the DR bit ("FIFO not full, but no
data received for 1.5 frames") as an indicator that data can be read.
Otherwise the driver will let data rot in the FIFO until the threshold
is reached.

Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
---
 drivers/tty/serial/sh-sci.c | 9 +++++----
 drivers/tty/serial/sh-sci.h | 1 +
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 385afbe..de25db8 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -677,7 +677,7 @@ static int sci_poll_get_char(struct uart_port *port)
 		break;
 	} while (1);
 
-	if (!(status & SCxSR_RDxF(port)))
+	if (!(status & (SCxSR_RDxF(port) | SCxSR_DR(port))))
 		return NO_POLL_CHAR;
 
 	c = serial_port_in(port, SCxRDR);
@@ -773,7 +773,8 @@ static int sci_rxfill(struct uart_port *port)
 	if (reg->size)
 		return serial_port_in(port, SCFDR) & ((port->fifosize << 1) - 1);
 
-	return (serial_port_in(port, SCxSR) & SCxSR_RDxF(port)) != 0;
+	return (serial_port_in(port, SCxSR) &
+		(SCxSR_RDxF(port) | SCxSR_DR(port))) != 0;
 }
 
 /*
@@ -864,7 +865,7 @@ static void sci_receive_chars(struct uart_port *port)
 	unsigned char flag;
 
 	status = serial_port_in(port, SCxSR);
-	if (!(status & SCxSR_RDxF(port)))
+	if (!(status & (SCxSR_RDxF(port) | SCxSR_DR(port))))
 		return;
 
 	while (1) {
@@ -1672,7 +1673,7 @@ static irqreturn_t sci_mpxed_interrupt(int irq, void *ptr)
 	 * Rx Interrupt: if we're using DMA, the DMA controller clears RDF /
 	 * DR flags
 	 */
-	if (((ssr_status & SCxSR_RDxF(port)) || s->chan_rx) &&
+	if (((ssr_status & (SCxSR_RDxF(port) | SCxSR_DR(port))) || s->chan_rx) &&
 	    (scr_status & SCSCR_RIE))
 		ret = sci_rx_interrupt(irq, ptr);
 
diff --git a/drivers/tty/serial/sh-sci.h b/drivers/tty/serial/sh-sci.h
index f51f919..44997a5 100644
--- a/drivers/tty/serial/sh-sci.h
+++ b/drivers/tty/serial/sh-sci.h
@@ -156,6 +156,7 @@ enum {
 #define SCxSR_FER(port)		(((port)->type == PORT_SCI) ? SCI_FER    : SCIF_FER)
 #define SCxSR_PER(port)		(((port)->type == PORT_SCI) ? SCI_PER    : SCIF_PER)
 #define SCxSR_BRK(port)		(((port)->type == PORT_SCI) ? 0x00       : SCIF_BRK)
+#define SCxSR_DR(port)		(((port)->type == PORT_SCI) ? 0x00       : SCIF_DR)
 
 #define SCxSR_ERRORS(port)	(to_sci_port(port)->error_mask)
 
-- 
2.7.4

  parent reply	other threads:[~2016-12-09 12:36 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-09 12:36 [PATCH 0/7] Renesas *SCIF* RX FIFO support Ulrich Hecht
2016-12-09 12:36 ` [PATCH 1/7] serial: sh-sci: add FIFO trigger bits Ulrich Hecht
2016-12-14 13:35   ` Geert Uytterhoeven
2016-12-09 12:36 ` Ulrich Hecht [this message]
2016-12-14 13:45   ` [PATCH 2/7] serial: sh-sci: consider DR (data ready) bit adequately Geert Uytterhoeven
2016-12-09 12:36 ` [PATCH 3/7] serial: sh-sci: implement FIFO threshold register setting Ulrich Hecht
2016-12-12 10:21   ` Sergei Shtylyov
2016-12-14 13:50   ` Geert Uytterhoeven
2016-12-09 12:36 ` [PATCH 4/7] serial: sh-sci: increase RX FIFO trigger defaults for (H)SCIF Ulrich Hecht
2016-12-14 13:58   ` Geert Uytterhoeven
2016-12-09 12:36 ` [PATCH 5/7] serial: sh-sci: SCIFA/B RX FIFO software timeout Ulrich Hecht
2016-12-14 14:02   ` Geert Uytterhoeven
2017-01-23 16:04     ` Ulrich Hecht
2016-12-09 12:36 ` [PATCH 6/7] serial: sh-sci: make RX FIFO parameters tunable via sysfs Ulrich Hecht
2016-12-14 14:04   ` Geert Uytterhoeven
2016-12-09 12:36 ` [PATCH 7/7] arm64: dts: r8a7796: salvator-x: add SCIF1 (DEBUG1) Ulrich Hecht
2016-12-14 14:10   ` Geert Uytterhoeven

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