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Message-ID: <504e19d0-05dd-dc80-3aaf-cdab8f88002d@gmail.com>
Date: Fri, 14 Jun 2019 20:51:51 +0300
From: Dmitry Osipenko <digetx@...il.com>
To: Bitan Biswas <bbiswas@...dia.com>,
Laxman Dewangan <ldewangan@...dia.com>,
Thierry Reding <treding@...dia.com>,
Jonathan Hunter <jonathanh@...dia.com>,
linux-i2c@...r.kernel.org, linux-tegra@...r.kernel.org,
linux-kernel@...r.kernel.org, Peter Rosin <peda@...ntia.se>,
Wolfram Sang <wsa@...-dreams.de>
Cc: Shardar Mohammed <smohammed@...dia.com>,
Sowjanya Komatineni <skomatineni@...dia.com>,
Mantravadi Karthik <mkarthik@...dia.com>
Subject: Re: [PATCH V6] i2c: tegra: remove BUG, BUG_ON
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 <bbiswas@...dia.com>
> ---
> 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.
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