From 3c77412b4a5e144bebf06cc668dc4b35b59b4607 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Thu, 23 Jan 2020 15:22:42 +0000 Subject: [PATCH] hw/char/exynos4210_uart: Add receive DMA support 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. Reviewed-by: Peter Maydell Signed-off-by: Guenter Roeck Message-id: 20200123052540.6132-8-linux@roeck-us.net Signed-off-by: Peter Maydell --- hw/char/exynos4210_uart.c | 24 ++++++++++++++++++++++++ hw/char/trace-events | 2 ++ 2 files changed, 26 insertions(+) diff --git a/hw/char/exynos4210_uart.c b/hw/char/exynos4210_uart.c index 363393cc75..20d8509107 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); } } @@ -495,6 +517,7 @@ 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; @@ -661,6 +684,7 @@ 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"