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[91.79.162.197]) by smtp.googlemail.com with ESMTPSA id g2sm229244wmh.0.2019.06.17.12.32.14 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 17 Jun 2019 12:32:15 -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> <504e19d0-05dd-dc80-3aaf-cdab8f88002d@gmail.com> From: Dmitry Osipenko Message-ID: Date: Mon, 17 Jun 2019 22:32:14 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: 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 17.06.2019 22:08, Bitan Biswas пишет: > > > On 6/14/19 10:51 AM, Dmitry Osipenko wrote: >> 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? > OK. > >> >>>   #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. >> > OK > >>>           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. > OK > >> >>> +    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. > OK. > > >> >>> +                (!(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. > OK > >> >>> +                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. > OK > >> >>> +                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. >> > > Sorry for the delayed reply. I shared Patch V7 with above changes earlier today. No problems, please take your time. The V7 is almost good, looking forward to v8!