diff mbox series

[5/6] hw/char/exynos4210_uart: Add receive DMA support

Message ID 20200110203942.5745-6-linux@roeck-us.net (mailing list archive)
State New, archived
Headers show
Series Fix Exynos4210 DMA support | expand

Commit Message

Guenter Roeck Jan. 10, 2020, 8:39 p.m. UTC 
To support receive DMA, we need to inform the DMA controller if receive data
is available. Otherwise the DMA controller keeps requesting data, causing
receive errors.

Implement this using an interrupt line. The instantiating code then needs
to connect the interrupt with the matching DMA controller GPIO pin.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 hw/char/exynos4210_uart.c | 24 ++++++++++++++++++++++++
 hw/char/trace-events      |  2 ++
 2 files changed, 26 insertions(+)

Comments

Peter Maydell Jan. 17, 2020, 1:44 p.m. UTC | #1 
On Fri, 10 Jan 2020 at 20:39, Guenter Roeck <linux@roeck-us.net> wrote:
>
> To support receive DMA, we need to inform the DMA controller if receive data
> is available. Otherwise the DMA controller keeps requesting data, causing
> receive errors.
>
> Implement this using an interrupt line. The instantiating code then needs
> to connect the interrupt with the matching DMA controller GPIO pin.
>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM
diff mbox series

Patch

diff --git a/hw/char/exynos4210_uart.c b/hw/char/exynos4210_uart.c
index 61134a7bdc..e23799f93b 100644
--- a/hw/char/exynos4210_uart.c
+++ b/hw/char/exynos4210_uart.c
@@ -154,6 +154,7 @@  typedef struct Exynos4210UartState {
 
     CharBackend       chr;
     qemu_irq          irq;
+    qemu_irq          dmairq;
 
     uint32_t channel;
 
@@ -261,6 +262,24 @@  exynos4210_uart_Rx_FIFO_trigger_level(const Exynos4210UartState *s)
     return exynos4210_uart_FIFO_trigger_level(s->channel, reg);
 }
 
+/*
+ * Update Rx DMA busy signal if Rx DMA is enabled. For simplicity,
+ * mark DMA as busy if DMA is enabled and the receive buffer is empty.
+ */
+static void exynos4210_uart_update_dmabusy(Exynos4210UartState *s)
+{
+    bool rx_dma_enabled = (s->reg[I_(UCON)] & 0x03) == 0x02;
+    uint32_t count = fifo_elements_number(&s->rx);
+
+    if (rx_dma_enabled && !count) {
+        qemu_irq_raise(s->dmairq);
+        trace_exynos_uart_dmabusy(s->channel);
+    } else {
+        qemu_irq_lower(s->dmairq);
+        trace_exynos_uart_dmaready(s->channel);
+    }
+}
+
 static void exynos4210_uart_update_irq(Exynos4210UartState *s)
 {
     /*
@@ -282,10 +301,12 @@  static void exynos4210_uart_update_irq(Exynos4210UartState *s)
         count = fifo_elements_number(&s->rx);
         if ((count && !(s->reg[I_(UCON)] & 0x80)) ||
             count >= exynos4210_uart_Rx_FIFO_trigger_level(s)) {
+            exynos4210_uart_update_dmabusy(s);
             s->reg[I_(UINTSP)] |= UINTSP_RXD;
             timer_del(s->fifo_timeout_timer);
         }
     } else if (s->reg[I_(UTRSTAT)] & UTRSTAT_Rx_BUFFER_DATA_READY) {
+        exynos4210_uart_update_dmabusy(s);
         s->reg[I_(UINTSP)] |= UINTSP_RXD;
     }
 
@@ -311,6 +332,7 @@  static void exynos4210_uart_timeout_int(void *opaque)
         (s->reg[I_(UCON)] & (1 << 11))) {
         s->reg[I_(UINTSP)] |= UINTSP_RXD;
         s->reg[I_(UTRSTAT)] |= UTRSTAT_Rx_TIMEOUT;
+        exynos4210_uart_update_dmabusy(s);
         exynos4210_uart_update_irq(s);
     }
 }
@@ -499,6 +521,7 @@  static uint64_t exynos4210_uart_read(void *opaque, hwaddr offset,
             s->reg[I_(UTRSTAT)] &= ~UTRSTAT_Rx_BUFFER_DATA_READY;
             res = s->reg[I_(URXH)];
         }
+        exynos4210_uart_update_dmabusy(s);
         trace_exynos_uart_read(s->channel, offset,
                                exynos4210_uart_regname(offset), res);
         return res;
@@ -654,6 +677,7 @@  static void exynos4210_uart_init(Object *obj)
     sysbus_init_mmio(dev, &s->iomem);
 
     sysbus_init_irq(dev, &s->irq);
+    sysbus_init_irq(dev, &s->dmairq);
 }
 
 static void exynos4210_uart_realize(DeviceState *dev, Error **errp)
diff --git a/hw/char/trace-events b/hw/char/trace-events
index cb73fee6a9..6f938301d9 100644
--- a/hw/char/trace-events
+++ b/hw/char/trace-events
@@ -79,6 +79,8 @@  nrf51_uart_read(uint64_t addr, uint64_t r, unsigned int size) "addr 0x%" PRIx64
 nrf51_uart_write(uint64_t addr, uint64_t value, unsigned int size) "addr 0x%" PRIx64 " value 0x%" PRIx64 " size %u"
 
 # exynos4210_uart.c
+exynos_uart_dmabusy(uint32_t channel) "UART%d: DMA busy (Rx buffer empty)"
+exynos_uart_dmaready(uint32_t channel) "UART%d: DMA ready"
 exynos_uart_irq_raised(uint32_t channel, uint32_t reg) "UART%d: IRQ raised: 0x%08"PRIx32
 exynos_uart_irq_lowered(uint32_t channel) "UART%d: IRQ lowered"
 exynos_uart_update_params(uint32_t channel, int speed, uint8_t parity, int data, int stop, uint64_t wordtime) "UART%d: speed: %d, parity: %c, data bits: %d, stop bits: %d wordtime: %"PRId64"ns"