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Tue, 11 May 2021 10:20:01 -0500 Received: from fllv0040.itg.ti.com (10.64.41.20) by DFLE108.ent.ti.com (10.64.6.29) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2 via Frontend Transport; Tue, 11 May 2021 10:20:01 -0500 Received: from ula0132425.ent.ti.com (ileax41-snat.itg.ti.com [10.172.224.153]) by fllv0040.itg.ti.com (8.15.2/8.15.2) with ESMTP id 14BFJwuG121251; Tue, 11 May 2021 10:19:59 -0500 From: Vignesh Raghavendra To: Greg Kroah-Hartman , Jiri Slaby CC: Vignesh Raghavendra , Jan Kiszka , , , Linux ARM Mailing List , Subject: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm Date: Tue, 11 May 2021 20:49:55 +0530 Message-ID: <20210511151955.28071-1-vigneshr@ti.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210511_082004_240313_2FE70214 X-CRM114-Status: GOOD ( 12.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org It is possible that RX TIMEOUT is signalled after RX FIFO has been drained, in which case a dummy read of RX FIFO is required to clear RX TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared leading to an interrupt storm Cc: stable@vger.kernel.org Reported-by: Jan Kiszka Signed-off-by: Vignesh Raghavendra --- drivers/tty/serial/8250/8250_omap.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index 8ac11eaeca51..c71bd766fa56 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -104,6 +104,9 @@ #define UART_OMAP_EFR2 0x23 #define UART_OMAP_EFR2_TIMEOUT_BEHAVE BIT(6) +/* RX FIFO occupancy indicator */ +#define UART_OMAP_RX_LVL 0x64 + struct omap8250_priv { int line; u8 habit; @@ -625,6 +628,15 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id) serial8250_rpm_get(up); iir = serial_port_in(port, UART_IIR); ret = serial8250_handle_irq(port, iir); + /* + * It is possible that RX TIMEOUT is signalled after FIFO + * has been drained, in which case a dummy read of RX FIFO is + * required to clear RX TIMEOUT condition. + */ + if ((iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT) { + if (serial_port_in(port, UART_OMAP_RX_LVL) == 0) + serial_port_in(port, UART_RX); + } serial8250_rpm_put(up); return IRQ_RETVAL(ret);