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[88.187.86.199]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43cee22c13fsm51483595e9.40.2025.03.09.18.28.59 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sun, 09 Mar 2025 18:29:00 -0700 (PDT) From: =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= To: qemu-devel@nongnu.org Cc: Peter Maydell , =?utf-8?q?Marc-Andr=C3=A9_Lure?= =?utf-8?q?au?= , =?utf-8?q?Alex_Benn=C3=A9e?= , Mark Cave-Ayland , qemu-arm@nongnu.org, Paolo Bonzini , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= Subject: [PATCH v7 6/7] hw/char/pl011: Drain TX FIFO when no backend connected Date: Mon, 10 Mar 2025 02:28:24 +0100 Message-ID: <20250310012825.79614-7-philmd@linaro.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250310012825.79614-1-philmd@linaro.org> References: <20250310012825.79614-1-philmd@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::430; envelope-from=philmd@linaro.org; helo=mail-wr1-x430.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org When no character backend is connected, the PL011 frontend just drains the FIFO. Signed-off-by: Philippe Mathieu-Daudé Reviewed-by: Peter Maydell --- hw/char/pl011.c | 13 +++++++++++++ hw/char/trace-events | 1 + 2 files changed, 14 insertions(+) diff --git a/hw/char/pl011.c b/hw/char/pl011.c index f67ce951ac9..6d26a3e13f8 100644 --- a/hw/char/pl011.c +++ b/hw/char/pl011.c @@ -241,6 +241,13 @@ static void pl011_loopback_tx(PL011State *s, uint32_t value) pl011_fifo_rx_put(s, value); } +static void pl011_drain_tx(PL011State *s) +{ + trace_pl011_fifo_tx_drain(fifo8_num_used(&s->xmit_fifo)); + pl011_reset_tx_fifo(s); + s->rsr &= ~RSR_OE; +} + static gboolean pl011_xmit_cb(void *do_not_use, GIOCondition cond, void *opaque) { PL011State *s = opaque; @@ -252,6 +259,12 @@ static gboolean pl011_xmit_cb(void *do_not_use, GIOCondition cond, void *opaque) count = fifo8_num_used(&s->xmit_fifo); trace_pl011_fifo_tx_xmit_used(count); + if (!qemu_chr_fe_backend_connected(&s->chr)) { + /* Instant drain the fifo when there's no back-end. */ + pl011_drain_tx(s); + return G_SOURCE_REMOVE; + } + buf[0] = fifo8_pop(&s->xmit_fifo); bytes_consumed = 1; diff --git a/hw/char/trace-events b/hw/char/trace-events index d52f511a1e2..730d6292a2d 100644 --- a/hw/char/trace-events +++ b/hw/char/trace-events @@ -71,6 +71,7 @@ pl011_fifo_tx_put(uint8_t byte) "TX FIFO push char [0x%02x]" pl011_fifo_tx_xmit_used(unsigned sent) "TX FIFO used %u chars" pl011_fifo_tx_xmit_consumed(unsigned sent) "TX FIFO consumed %u chars" pl011_fifo_tx_overrun(void) "TX FIFO overrun" +pl011_fifo_tx_drain(unsigned drained) "TX FIFO draining %u chars" pl011_baudrate_change(unsigned int baudrate, uint64_t clock, uint32_t ibrd, uint32_t fbrd) "new baudrate %u (clk: %" PRIu64 "hz, ibrd: %" PRIu32 ", fbrd: %" PRIu32 ")" pl011_receive(int size) "recv %d chars"