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[91.79.162.197]) by smtp.googlemail.com with ESMTPSA id e8sm641735lfc.27.2019.06.14.10.51.51 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 14 Jun 2019 10:51:52 -0700 (PDT) Subject: Re: [PATCH V6] i2c: tegra: remove BUG, BUG_ON To: Bitan Biswas , Laxman Dewangan , Thierry Reding , Jonathan Hunter , linux-i2c@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Rosin , Wolfram Sang Cc: Shardar Mohammed , Sowjanya Komatineni , Mantravadi Karthik References: <1560527438-30150-1-git-send-email-bbiswas@nvidia.com> From: Dmitry Osipenko Message-ID: <504e19d0-05dd-dc80-3aaf-cdab8f88002d@gmail.com> Date: Fri, 14 Jun 2019 20:51:51 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <1560527438-30150-1-git-send-email-bbiswas@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 14.06.2019 18:50, Bitan Biswas пишет: > Remove redundant BUG_ON calls or replace with WARN_ON_ONCE > as needed. Remove BUG() and mask Rx interrupt similar as Tx > for message fully sent case. Add WARN_ON_ONCE check > for non-zero rx_fifo_avail in tegra_i2c_empty_rx_fifo() > after all processing. Error handling in tegra_i2c_empty_rx_fifo > caller is also added. > > Signed-off-by: Bitan Biswas > --- > drivers/i2c/busses/i2c-tegra.c | 46 ++++++++++++++++++++++++++++++++++-------- > 1 file changed, 38 insertions(+), 8 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c > index 4dfb4c1..26a7c8c 100644 > --- a/drivers/i2c/busses/i2c-tegra.c > +++ b/drivers/i2c/busses/i2c-tegra.c > @@ -73,6 +73,7 @@ > #define I2C_ERR_NO_ACK BIT(0) > #define I2C_ERR_ARBITRATION_LOST BIT(1) > #define I2C_ERR_UNKNOWN_INTERRUPT BIT(2) > +#define I2C_ERR_UNEXPECTED_STATUS BIT(3) What about I2C_ERR_RX_BUFFER_OVERFLOW? > #define PACKET_HEADER0_HEADER_SIZE_SHIFT 28 > #define PACKET_HEADER0_PACKET_ID_SHIFT 16 > @@ -515,15 +516,23 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev) > * prevent overwriting past the end of buf > */ > if (rx_fifo_avail > 0 && buf_remaining > 0) { > - BUG_ON(buf_remaining > 3); > + /* buf_remaining > 3 check not needed as rx_fifo_avail == 0 > + * when (words_to_transfer was > rx_fifo_avail) earlier > + * in this function > + */ Please start all multiline comments with an empty "/*", it should be the correct style. There are some places in the kernel where style like yours is used, but I assume they are not very correct. Besides, yours variant is not consistent with the style of the rest of comments in this source file. And put a dot in the end for completeness. Same for the other comments in this patch. > val = i2c_readl(i2c_dev, I2C_RX_FIFO); > val = cpu_to_le32(val); > memcpy(buf, &val, buf_remaining); > buf_remaining = 0; > rx_fifo_avail--; > } Please add a newline here. All logical parts of the code should be separated to ease reading and following. > + if (WARN_ON_ONCE(rx_fifo_avail)) > + return -EINVAL; > > - BUG_ON(rx_fifo_avail > 0 && buf_remaining > 0); > + /* buf_remaining > 0 at this point can only have rx_fifo_avail == 0 > + * as this corresponds to (words_to_transfer was > rx_fifo_avail) > + * case earlier in this function > + */ > i2c_dev->msg_buf_remaining = buf_remaining; > i2c_dev->msg_buf = buf; > > @@ -581,7 +590,10 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev) > * boundary and fault. > */ > if (tx_fifo_avail > 0 && buf_remaining > 0) { > - BUG_ON(buf_remaining > 3); > + /* buf_remaining > 3 check not needed as tx_fifo_avail == 0 > + * when (words_to_transfer was > tx_fifo_avail) earlier > + * in this function for non-zero words_to_transfer > + */ > memcpy(&val, buf, buf_remaining); > val = le32_to_cpu(val); > > @@ -811,6 +823,7 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) > u32 status; > const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST; > struct tegra_i2c_dev *i2c_dev = dev_id; > + int err_val; > > status = i2c_readl(i2c_dev, I2C_INT_STATUS); > > @@ -847,10 +860,21 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) > > if (!i2c_dev->is_curr_dma_xfer) { > if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) { > - if (i2c_dev->msg_buf_remaining) > - tegra_i2c_empty_rx_fifo(i2c_dev); > - else > - BUG(); > + err_val = tegra_i2c_empty_rx_fifo(i2c_dev); > + if ((!(i2c_dev->msg_buf_remaining)) && Let's move this check into tegra_i2c_empty_rx_fifo() and return -EINVAL for that case. This will make code to look cleaner. > + (!(status & I2C_INT_PACKET_XFER_COMPLETE)) && It shouldn't matter that XFER_COMPLETE is set if RX FIFO isn't fully emptied because it always shall be emptied. Hence this check is not needed and we should error out regardless. > + err_val) { > + /* > + * Overflow error condition: message fully sent, > + * with no XFER_COMPLETE interrupt but hardware > + * asks to transfer more. > + */ > + tegra_i2c_mask_irq(i2c_dev, > + I2C_INT_RX_FIFO_DATA_REQ); No need to mask RX_FIFO_DATA_REQ here because all interrupts are masked on "goto err:", hence just remove the tegra_i2c_mask_irq(). > + i2c_dev->msg_err |= > + I2C_ERR_UNEXPECTED_STATUS; No need to split this into two lines because it's less than 80 chars, write this in a single line. > + goto err; > + } > } > > if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) { > @@ -876,7 +900,13 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) > if (status & I2C_INT_PACKET_XFER_COMPLETE) { > if (i2c_dev->is_curr_dma_xfer) > i2c_dev->msg_buf_remaining = 0; > - BUG_ON(i2c_dev->msg_buf_remaining); > + /* Underflow error condition: XFER_COMPLETE before message > + * fully sent. > + */ > + if (WARN_ON_ONCE(i2c_dev->msg_buf_remaining)) { > + i2c_dev->msg_err |= I2C_ERR_UNKNOWN_INTERRUPT; > + goto err; > + } > complete(&i2c_dev->msg_complete); > } > goto done; > Please address comments in the next revision.