Messages in this thread | | | Subject | Re: [PATCH V7] i2c: tegra: remove BUG, BUG_ON | From | Bitan Biswas <> | Date | Mon, 17 Jun 2019 11:41:00 -0700 |
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On 6/17/19 5:13 AM, Dmitry Osipenko wrote: > 17.06.2019 8:09, Bitan Biswas пишет: >> Remove BUG, BUG_ON as it makes system usable: >> - 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 caller error handling and WARN_ON_ONCE check for non-zero >> rx_fifo_avail in tegra_i2c_empty_rx_fifo() after all processing. > > The commit message should describe motivation of the change and not the change itself, > unless it's some additional information which is required for better understanding of > the code. > > In yours case it could be something like that: > > The usage of BUG() macro is generally discouraged in kernel, unless > it's a problem that results in a physical damage or loss of data. > This patch removes unnecessary BUG() macros and replaces the rest > with a warnings. I shall update as per above comments.
> >> Signed-off-by: Bitan Biswas <bbiswas@nvidia.com> >> --- >> drivers/i2c/busses/i2c-tegra.c | 45 ++++++++++++++++++++++++++++++++++-------- >> 1 file changed, 37 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c >> index 4dfb4c1..b155b61 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_RX_BUFFER_OVERFLOW BIT(3) >> >> #define PACKET_HEADER0_HEADER_SIZE_SHIFT 28 >> #define PACKET_HEADER0_PACKET_ID_SHIFT 16 >> @@ -515,7 +516,11 @@ 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. >> + */ >> val = i2c_readl(i2c_dev, I2C_RX_FIFO); >> val = cpu_to_le32(val); >> memcpy(buf, &val, buf_remaining); >> @@ -523,7 +528,15 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev) >> rx_fifo_avail--; >> } >> >> - BUG_ON(rx_fifo_avail > 0 && buf_remaining > 0); >> + if ((!(i2c_dev->msg_buf_remaining)) && > > The RX FIFO shall be drained completely no matter what. > > Hence why the "i2c_dev->msg_buf_remaining" checking is needed here? I moved the part of below condition in Patch V6 to function tegra_i2c_empty_rx_fifo:
>> + 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.
Is above condition not needed?
> > Secondly, in the future please don't add parens where they are not needed. In this > case parens around !i2c_dev->msg_buf_remaining are not needed at all. > I shall look out for similar unnecessary parentheses and update the patch.
>> + WARN_ON_ONCE(rx_fifo_avail)) >> + return -EINVAL; >> + >> + /* >> + * buf_remaining > 0 at this point can only have rx_fifo_avail == 0 > > The rx_fifo_avail is always 0 at this point, including the case of buf_remaining == 0. > It will be better if you'll add a comment for the WARN_ON_ONCE(rx_fifo_avail) above, > saying that RX FIFO must be fully drained, and then just drop this comment. >
OK.
>> + * 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; > > [snip] >
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