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[2403:580b:97e8:0:82ce:f179:8a79:69f4]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-718e58c68d3sm2528155b3a.84.2024.09.08.19.13.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Sep 2024 19:13:37 -0700 (PDT) From: Alistair Francis X-Google-Original-From: Alistair Francis To: alex.bennee@linaro.org, qemu-devel@nongnu.org, peter.maydell@linaro.org Cc: dbarboza@ventanamicro.com, palmer@dabbelt.com, zhiwei_liu@linux.alibaba.com, qemu-riscv@nongnu.org, Paolo Bonzini , alistair23@gmail.com, Bin Meng , liwei1518@gmail.com, Alistair Francis , =?utf-8?q?Marc-Andr=C3=A9_Lure?= =?utf-8?q?au?= , atishp@rivosinc.com, Alistair Francis , Thomas Huth Subject: [PATCH v3 2/2] hw/char: sifive_uart: Print uart characters async Date: Mon, 9 Sep 2024 12:13:17 +1000 Message-ID: <20240909021317.58192-3-alistair.francis@wdc.com> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240909021317.58192-1-alistair.francis@wdc.com> References: <20240909021317.58192-1-alistair.francis@wdc.com> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::52e; envelope-from=alistair23@gmail.com; helo=mail-pg1-x52e.google.com X-Spam_score_int: -17 X-Spam_score: -1.8 X-Spam_bar: - X-Spam_report: (-1.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org The current approach of using qemu_chr_fe_write() and ignoring the return values results in dropped characters [1]. Let's update the SiFive UART to use a async sifive_uart_xmit() function to transmit the characters and apply back pressure to the guest with the SIFIVE_UART_TXFIFO_FULL status. This should avoid dropped characters and more realisticly model the hardware. 1: https://gitlab.com/qemu-project/qemu/-/issues/2114 Signed-off-by: Alistair Francis Tested-by: Thomas Huth Reviewed-by: Daniel Henrique Barboza --- include/hw/char/sifive_uart.h | 17 ++++++- hw/char/sifive_uart.c | 88 +++++++++++++++++++++++++++++++++-- 2 files changed, 99 insertions(+), 6 deletions(-) diff --git a/include/hw/char/sifive_uart.h b/include/hw/char/sifive_uart.h index 7f6c79f8bd..b43109bb8b 100644 --- a/include/hw/char/sifive_uart.h +++ b/include/hw/char/sifive_uart.h @@ -24,6 +24,7 @@ #include "hw/qdev-properties.h" #include "hw/sysbus.h" #include "qom/object.h" +#include "qemu/fifo8.h" enum { SIFIVE_UART_TXFIFO = 0, @@ -48,9 +49,13 @@ enum { SIFIVE_UART_IP_RXWM = 2 /* Receive watermark interrupt pending */ }; +#define SIFIVE_UART_TXFIFO_FULL 0x80000000 + #define SIFIVE_UART_GET_TXCNT(txctrl) ((txctrl >> 16) & 0x7) #define SIFIVE_UART_GET_RXCNT(rxctrl) ((rxctrl >> 16) & 0x7) + #define SIFIVE_UART_RX_FIFO_SIZE 8 +#define SIFIVE_UART_TX_FIFO_SIZE 8 #define TYPE_SIFIVE_UART "riscv.sifive.uart" OBJECT_DECLARE_SIMPLE_TYPE(SiFiveUARTState, SIFIVE_UART) @@ -63,13 +68,21 @@ struct SiFiveUARTState { qemu_irq irq; MemoryRegion mmio; CharBackend chr; - uint8_t rx_fifo[SIFIVE_UART_RX_FIFO_SIZE]; - uint8_t rx_fifo_len; + + uint32_t txfifo; uint32_t ie; uint32_t ip; uint32_t txctrl; uint32_t rxctrl; uint32_t div; + + uint8_t rx_fifo[SIFIVE_UART_RX_FIFO_SIZE]; + uint8_t rx_fifo_len; + + Fifo8 tx_fifo; + + QEMUTimer *fifo_trigger_handle; + uint64_t char_tx_time; }; SiFiveUARTState *sifive_uart_create(MemoryRegion *address_space, hwaddr base, diff --git a/hw/char/sifive_uart.c b/hw/char/sifive_uart.c index 7fc6787f69..ab899b60d6 100644 --- a/hw/char/sifive_uart.c +++ b/hw/char/sifive_uart.c @@ -64,6 +64,72 @@ static void sifive_uart_update_irq(SiFiveUARTState *s) } } +static gboolean sifive_uart_xmit(void *do_not_use, GIOCondition cond, + void *opaque) +{ + SiFiveUARTState *s = opaque; + int ret; + const uint8_t *charecters; + uint32_t numptr = 0; + + /* instant drain the fifo when there's no back-end */ + if (!qemu_chr_fe_backend_connected(&s->chr)) { + fifo8_reset(&s->tx_fifo); + return G_SOURCE_REMOVE; + } + + if (fifo8_is_empty(&s->tx_fifo)) { + return G_SOURCE_REMOVE; + } + + /* Don't pop the FIFO in case the write fails */ + charecters = fifo8_peek_bufptr(&s->tx_fifo, + fifo8_num_used(&s->tx_fifo), &numptr); + ret = qemu_chr_fe_write(&s->chr, charecters, numptr); + + if (ret >= 0) { + /* We wrote the data, actually pop the fifo */ + fifo8_pop_bufptr(&s->tx_fifo, ret, NULL); + } + + if (!fifo8_is_empty(&s->tx_fifo)) { + guint r = qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP, + sifive_uart_xmit, s); + if (!r) { + fifo8_reset(&s->tx_fifo); + return G_SOURCE_REMOVE; + } + } + + /* Clear the TX Full bit */ + if (!fifo8_is_full(&s->tx_fifo)) { + s->txfifo &= ~SIFIVE_UART_TXFIFO_FULL; + } + + sifive_uart_update_irq(s); + return G_SOURCE_REMOVE; +} + +static void sifive_uart_write_tx_fifo(SiFiveUARTState *s, const uint8_t *buf, + int size) +{ + uint64_t current_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); + + if (size > fifo8_num_free(&s->tx_fifo)) { + size = fifo8_num_free(&s->tx_fifo); + qemu_log_mask(LOG_GUEST_ERROR, "sifive_uart: TX FIFO overflow"); + } + + fifo8_push_all(&s->tx_fifo, buf, size); + + if (fifo8_is_full(&s->tx_fifo)) { + s->txfifo |= SIFIVE_UART_TXFIFO_FULL; + } + + timer_mod(s->fifo_trigger_handle, current_time + + (s->char_tx_time * 4)); +} + static uint64_t sifive_uart_read(void *opaque, hwaddr addr, unsigned int size) { @@ -82,7 +148,7 @@ sifive_uart_read(void *opaque, hwaddr addr, unsigned int size) return 0x80000000; case SIFIVE_UART_TXFIFO: - return 0; /* Should check tx fifo */ + return s->txfifo; case SIFIVE_UART_IE: return s->ie; case SIFIVE_UART_IP: @@ -106,12 +172,10 @@ sifive_uart_write(void *opaque, hwaddr addr, { SiFiveUARTState *s = opaque; uint32_t value = val64; - unsigned char ch = value; switch (addr) { case SIFIVE_UART_TXFIFO: - qemu_chr_fe_write(&s->chr, &ch, 1); - sifive_uart_update_irq(s); + sifive_uart_write_tx_fifo(s, (uint8_t *) &value, 1); return; case SIFIVE_UART_IE: s->ie = val64; @@ -131,6 +195,13 @@ sifive_uart_write(void *opaque, hwaddr addr, __func__, (int)addr, (int)value); } +static void fifo_trigger_update(void *opaque) +{ + SiFiveUARTState *s = opaque; + + sifive_uart_xmit(NULL, G_IO_OUT, s); +} + static const MemoryRegionOps sifive_uart_ops = { .read = sifive_uart_read, .write = sifive_uart_write, @@ -197,6 +268,9 @@ static void sifive_uart_realize(DeviceState *dev, Error **errp) { SiFiveUARTState *s = SIFIVE_UART(dev); + s->fifo_trigger_handle = timer_new_ns(QEMU_CLOCK_VIRTUAL, + fifo_trigger_update, s); + qemu_chr_fe_set_handlers(&s->chr, sifive_uart_can_rx, sifive_uart_rx, sifive_uart_event, sifive_uart_be_change, s, NULL, true); @@ -206,12 +280,18 @@ static void sifive_uart_realize(DeviceState *dev, Error **errp) static void sifive_uart_reset_enter(Object *obj, ResetType type) { SiFiveUARTState *s = SIFIVE_UART(obj); + + s->txfifo = 0; s->ie = 0; s->ip = 0; s->txctrl = 0; s->rxctrl = 0; s->div = 0; + s->rx_fifo_len = 0; + + memset(s->rx_fifo, 0, SIFIVE_UART_RX_FIFO_SIZE); + fifo8_create(&s->tx_fifo, SIFIVE_UART_TX_FIFO_SIZE); } static void sifive_uart_reset_hold(Object *obj, ResetType type)