Author: ian
Date: Sun Oct 12 17:56:02 2014
New Revision: 273004
URL: https://svnweb.freebsd.org/changeset/base/273004
Log:
Use the FIFOs in the imx5/imx6 uart hardware instead of interrupting on
each byte sent or received.
Modified:
head/sys/dev/uart/uart_dev_imx.c
Modified: head/sys/dev/uart/uart_dev_imx.c
==============================================================================
--- head/sys/dev/uart/uart_dev_imx.c Sun Oct 12 17:50:25 2014
(r273003)
+++ head/sys/dev/uart/uart_dev_imx.c Sun Oct 12 17:56:02 2014
(r273004)
@@ -49,6 +49,17 @@ __FBSDID("$FreeBSD$");
#include <arm/freescale/imx/imx_ccmvar.h>
/*
+ * The hardare FIFOs are 32 bytes. We want an interrupt when there are 24
bytes
+ * available to read or space for 24 more bytes to write. While 8 bytes of
+ * slack before over/underrun might seem excessive, the hardware can run at
+ * 5mbps, which means 2uS per char, so at full speed 8 bytes provides only 16uS
+ * to get into the interrupt handler and service the fifo.
+ */
+#define IMX_FIFOSZ 32
+#define IMX_RXFIFO_LEVEL 24
+#define IMX_TXFIFO_LEVEL 24
+
+/*
* Low-level UART interface.
*/
static int imx_uart_probe(struct uart_bas *bas);
@@ -187,6 +198,17 @@ imx_uart_init(struct uart_bas *bas, int
SETREG(bas, REG(UBIR), 15);
SETREG(bas, REG(UBMR), (baseclk / baudrate) - 1);
}
+
+ /*
+ * Program the tx lowater and rx hiwater levels at which fifo-service
+ * interrupts are signaled. The tx value is interpetted as "when there
+ * are only this many bytes remaining" (not "this many free").
+ */
+ reg = GETREG(bas, REG(UFCR));
+ reg &= ~(IMXUART_UFCR_TXTL_MASK | IMXUART_UFCR_RXTL_MASK);
+ reg |= (IMX_FIFOSZ - IMX_TXFIFO_LEVEL) << IMXUART_UFCR_TXTL_SHIFT;
+ reg |= IMX_RXFIFO_LEVEL << IMXUART_UFCR_RXTL_SHIFT;
+ SETREG(bas, REG(UFCR), reg);
}
static void
@@ -199,7 +221,7 @@ static void
imx_uart_putc(struct uart_bas *bas, int c)
{
- while (!(IS(bas, USR2, TXFE)))
+ while (!(IS(bas, USR1, TRDY)))
;
SETREG(bas, REG(UTXD), c);
}
@@ -302,11 +324,15 @@ imx_uart_bus_attach(struct uart_softc *s
(void)imx_uart_bus_getsig(sc);
- ENA(bas, UCR4, DREN);
- DIS(bas, UCR1, RRDYEN);
+ /* Clear all pending interrupts. */
+ SETREG(bas, REG(USR1), 0xffff);
+ SETREG(bas, REG(USR2), 0xffff);
+
+ DIS(bas, UCR4, DREN);
+ ENA(bas, UCR1, RRDYEN);
DIS(bas, UCR1, IDEN);
DIS(bas, UCR3, RXDSEN);
- DIS(bas, UCR2, ATEN);
+ ENA(bas, UCR2, ATEN);
DIS(bas, UCR1, TXMPTYEN);
DIS(bas, UCR1, TRDYEN);
DIS(bas, UCR4, TCEN);
@@ -330,9 +356,6 @@ imx_uart_bus_attach(struct uart_softc *s
ENA(bas, UCR2, IRTS);
ENA(bas, UCR3, RXDMUXSEL);
- /* ACK all interrupts */
- SETREG(bas, REG(USR1), 0xffff);
- SETREG(bas, REG(USR2), 0xffff);
return (0);
}
@@ -404,7 +427,7 @@ imx_uart_bus_ipend(struct uart_softc *sc
struct uart_bas *bas;
int ipend;
uint32_t usr1, usr2;
- uint32_t ucr1, ucr4;
+ uint32_t ucr1, ucr2, ucr4;
bas = &sc->sc_bas;
ipend = 0;
@@ -419,18 +442,28 @@ imx_uart_bus_ipend(struct uart_softc *sc
SETREG(bas, REG(USR2), usr2);
ucr1 = GETREG(bas, REG(UCR1));
+ ucr2 = GETREG(bas, REG(UCR2));
ucr4 = GETREG(bas, REG(UCR4));
- if ((usr2 & FLD(USR2, TXFE)) && (ucr1 & FLD(UCR1, TXMPTYEN))) {
- DIS(bas, UCR1, TXMPTYEN);
- /* Continue TXing */
+ /* If we have reached tx low-water, we can tx some more now. */
+ if ((usr1 & FLD(USR1, TRDY)) && (ucr1 & FLD(UCR1, TRDYEN))) {
+ DIS(bas, UCR1, TRDYEN);
ipend |= SER_INT_TXIDLE;
}
- if ((usr2 & FLD(USR2, RDR)) && (ucr4 & FLD(UCR4, DREN))) {
- DIS(bas, UCR4, DREN);
- /* Wow, new char on input */
+
+ /*
+ * If we have reached the rx high-water, or if there are bytes in the rx
+ * fifo and no new data has arrived for 8 character periods (aging
+ * timer), we have input data to process.
+ */
+ if (((usr1 & FLD(USR1, RRDY)) && (ucr1 & FLD(UCR1, RRDYEN))) ||
+ ((usr1 & FLD(USR1, AGTIM)) && (ucr2 & FLD(UCR2, ATEN)))) {
+ DIS(bas, UCR1, RRDYEN);
+ DIS(bas, UCR2, ATEN);
ipend |= SER_INT_RXREADY;
}
+
+ /* A break can come in at any time, it never gets disabled. */
if ((usr2 & FLD(USR2, BRCD)) && (ucr4 & FLD(UCR4, BKEN)))
ipend |= SER_INT_BREAK;
@@ -459,8 +492,14 @@ imx_uart_bus_probe(struct uart_softc *sc
if (error)
return (error);
- sc->sc_rxfifosz = 1;
- sc->sc_txfifosz = 1;
+ /*
+ * On input we can read up to the full fifo size at once. On output, we
+ * want to write only as much as the programmed tx low water level,
+ * because that's all we can be certain we have room for in the fifo
+ * when we get a tx-ready interrupt.
+ */
+ sc->sc_rxfifosz = IMX_FIFOSZ;
+ sc->sc_txfifosz = IMX_TXFIFO_LEVEL;
device_set_desc(sc->sc_dev, "Freescale i.MX UART");
return (0);
@@ -475,20 +514,20 @@ imx_uart_bus_receive(struct uart_softc *
bas = &sc->sc_bas;
uart_lock(sc->sc_hwmtx);
- /* Read while we have anything in FIFO */
+ /*
+ * Empty the rx fifo. We get the RRDY interrupt when IMX_RXFIFO_LEVEL
+ * (the rx high-water level) is reached, but we set sc_rxfifosz to the
+ * full hardware fifo size, so we can safely process however much is
+ * there, not just the highwater size.
+ */
while (IS(bas, USR2, RDR)) {
if (uart_rx_full(sc)) {
/* No space left in input buffer */
sc->sc_rxbuf[sc->sc_rxput] = UART_STAT_OVERRUN;
break;
}
- out = 0;
xc = GETREG(bas, REG(URXD));
-
- /* We have valid char */
- if (xc & FLD(URXD, CHARRDY))
- out = xc & 0x000000ff;
-
+ out = xc & 0x000000ff;
if (xc & FLD(URXD, FRMERR))
out |= UART_STAT_FRAMERR;
if (xc & FLD(URXD, PRERR))
@@ -500,8 +539,8 @@ imx_uart_bus_receive(struct uart_softc *
uart_rx_put(sc, out);
}
- /* Reenable Data Ready interrupt */
- ENA(bas, UCR4, DREN);
+ ENA(bas, UCR1, RRDYEN);
+ ENA(bas, UCR2, ATEN);
uart_unlock(sc->sc_hwmtx);
return (0);
@@ -523,14 +562,17 @@ imx_uart_bus_transmit(struct uart_softc
bas = &sc->sc_bas;
uart_lock(sc->sc_hwmtx);
- /* Fill TX FIFO */
+ /*
+ * Fill the tx fifo. The uart core puts at most IMX_TXFIFO_LEVEL bytes
+ * into the txbuf (because that's what sc_txfifosz is set to), and
+ * because we got the TRDY (low-water reached) interrupt we know at
+ * least that much space is available in the fifo.
+ */
for (i = 0; i < sc->sc_txdatasz; i++) {
SETREG(bas, REG(UTXD), sc->sc_txbuf[i] & 0xff);
}
-
sc->sc_txbusy = 1;
- /* Call me when ready */
- ENA(bas, UCR1, TXMPTYEN);
+ ENA(bas, UCR1, TRDYEN);
uart_unlock(sc->sc_hwmtx);
@@ -544,7 +586,8 @@ imx_uart_bus_grab(struct uart_softc *sc)
bas = &sc->sc_bas;
uart_lock(sc->sc_hwmtx);
- DIS(bas, UCR4, DREN);
+ DIS(bas, UCR1, RRDYEN);
+ DIS(bas, UCR2, ATEN);
uart_unlock(sc->sc_hwmtx);
}
@@ -555,6 +598,7 @@ imx_uart_bus_ungrab(struct uart_softc *s
bas = &sc->sc_bas;
uart_lock(sc->sc_hwmtx);
- ENA(bas, UCR4, DREN);
+ ENA(bas, UCR1, RRDYEN);
+ ENA(bas, UCR2, ATEN);
uart_unlock(sc->sc_hwmtx);
}
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