From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= Subject: [PATCH v4 1/7] i2c: bcm2835: Fix hang for writing messages larger than 16 bytes Date: Mon, 3 Oct 2016 22:06:08 +0200 Message-ID: <1475525174-28604-2-git-send-email-noralf@tronnes.org> References: <1475525174-28604-1-git-send-email-noralf@tronnes.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: Received: from smtp.domeneshop.no ([194.63.252.55]:43240 "EHLO smtp.domeneshop.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751613AbcJCUGo (ORCPT ); Mon, 3 Oct 2016 16:06:44 -0400 In-Reply-To: <1475525174-28604-1-git-send-email-noralf@tronnes.org> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: wsa@the-dreams.de, swarren@wwwdotorg.org, eric@anholt.net Cc: linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rpi-kernel@lists.infradead.org, =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= Writing messages larger than the FIFO size results in a hang, rendering the machine unusable. This is because the RXD status flag is set on the first interrupt which results in bcm2835_drain_rxfifo() stealing bytes from the buffer. The controller continues to trigger interrupts waiting for the missing bytes, but bcm2835_fill_txfifo() has none to give. In this situation wait_for_completion_timeout() apparently is unable to stop the madness. The BCM2835 ARM Peripherals datasheet has this to say about the flags: TXD: is set when the FIFO has space for at least one byte of data. RXD: is set when the FIFO contains at least one byte of data. TXW: is set during a write transfer and the FIFO is less than full. RXR: is set during a read transfer and the FIFO is or more full. Implementing the logic from the downstream i2c-bcm2708 driver solved the hang problem. Signed-off-by: Noralf Trønnes Reviewed-by: Eric Anholt Reviewed-by: Martin Sperl --- drivers/i2c/busses/i2c-bcm2835.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c index d4f3239..f283b71 100644 --- a/drivers/i2c/busses/i2c-bcm2835.c +++ b/drivers/i2c/busses/i2c-bcm2835.c @@ -64,6 +64,7 @@ struct bcm2835_i2c_dev { int irq; struct i2c_adapter adapter; struct completion completion; + struct i2c_msg *curr_msg; u32 msg_err; u8 *msg_buf; size_t msg_buf_remaining; @@ -126,14 +127,13 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data) return IRQ_HANDLED; } - if (val & BCM2835_I2C_S_RXD) { - bcm2835_drain_rxfifo(i2c_dev); - if (!(val & BCM2835_I2C_S_DONE)) - return IRQ_HANDLED; - } - if (val & BCM2835_I2C_S_DONE) { - if (i2c_dev->msg_buf_remaining) + if (i2c_dev->curr_msg->flags & I2C_M_RD) { + bcm2835_drain_rxfifo(i2c_dev); + val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S); + } + + if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining) i2c_dev->msg_err = BCM2835_I2C_S_LEN; else i2c_dev->msg_err = 0; @@ -141,11 +141,16 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data) return IRQ_HANDLED; } - if (val & BCM2835_I2C_S_TXD) { + if (val & BCM2835_I2C_S_TXW) { bcm2835_fill_txfifo(i2c_dev); return IRQ_HANDLED; } + if (val & BCM2835_I2C_S_RXR) { + bcm2835_drain_rxfifo(i2c_dev); + return IRQ_HANDLED; + } + return IRQ_NONE; } @@ -155,6 +160,7 @@ static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev, u32 c; unsigned long time_left; + i2c_dev->curr_msg = msg; i2c_dev->msg_buf = msg->buf; i2c_dev->msg_buf_remaining = msg->len; reinit_completion(&i2c_dev->completion); -- 2.8.2