From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bitan Biswas Subject: Re: [PATCH V6] i2c: tegra: remove BUG, BUG_ON Date: Mon, 17 Jun 2019 12:08:06 -0700 Message-ID: References: <1560527438-30150-1-git-send-email-bbiswas@nvidia.com> <504e19d0-05dd-dc80-3aaf-cdab8f88002d@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <504e19d0-05dd-dc80-3aaf-cdab8f88002d@gmail.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Dmitry Osipenko , 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 List-Id: linux-tegra@vger.kernel.org On 6/14/19 10:51 AM, Dmitry Osipenko wrote: > 14.06.2019 18:50, Bitan Biswas =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> 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-teg= ra.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) >=20 > What about I2C_ERR_RX_BUFFER_OVERFLOW? OK. >=20 >> #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_i2= c_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 =3D=3D 0 >> + * when (words_to_transfer was > rx_fifo_avail) earlier >> + * in this function >> + */ >=20 > 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 consisten= t with the > style of the rest of comments in this source file. And put a dot in the e= nd for > completeness. Same for the other comments in this patch. >=20 OK >> val =3D i2c_readl(i2c_dev, I2C_RX_FIFO); >> val =3D cpu_to_le32(val); >> memcpy(buf, &val, buf_remaining); >> buf_remaining =3D 0; >> rx_fifo_avail--; >> } >=20 > Please add a newline here. All logical parts of the code should be separa= ted to ease > reading and following. OK >=20 >> + if (WARN_ON_ONCE(rx_fifo_avail)) >> + return -EINVAL; >> =20 >> - BUG_ON(rx_fifo_avail > 0 && buf_remaining > 0); >> + /* buf_remaining > 0 at this point can only have rx_fifo_avail =3D=3D = 0 >> + * as this corresponds to (words_to_transfer was > rx_fifo_avail) >> + * case earlier in this function >> + */ >> i2c_dev->msg_buf_remaining =3D buf_remaining; >> i2c_dev->msg_buf =3D buf; >> =20 >> @@ -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 =3D=3D 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 =3D le32_to_cpu(val); >> =20 >> @@ -811,6 +823,7 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_= id) >> u32 status; >> const u32 status_err =3D I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST; >> struct tegra_i2c_dev *i2c_dev =3D dev_id; >> + int err_val; >> =20 >> status =3D i2c_readl(i2c_dev, I2C_INT_STATUS); >> =20 >> @@ -847,10 +860,21 @@ static irqreturn_t tegra_i2c_isr(int irq, void *de= v_id) >> =20 >> 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 =3D tegra_i2c_empty_rx_fifo(i2c_dev); >> + if ((!(i2c_dev->msg_buf_remaining)) && >=20 > Let's move this check into tegra_i2c_empty_rx_fifo() and return -EINVAL f= or that case. > This will make code to look cleaner. OK. >=20 >> + (!(status & I2C_INT_PACKET_XFER_COMPLETE)) && >=20 > It shouldn't matter that XFER_COMPLETE is set if RX FIFO isn't fully empt= ied because > it always shall be emptied. Hence this check is not needed and we should = error out > regardless. OK >=20 >> + 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); >=20 > No need to mask RX_FIFO_DATA_REQ here because all interrupts are masked o= n "goto > err:", hence just remove the tegra_i2c_mask_irq(). >=20 >> + i2c_dev->msg_err |=3D >> + I2C_ERR_UNEXPECTED_STATUS; >=20 > No need to split this into two lines because it's less than 80 chars, wri= te this in a > single line. OK >=20 >> + goto err; >> + } >> } >> =20 >> 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 =3D 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 |=3D I2C_ERR_UNKNOWN_INTERRUPT; >> + goto err; >> + } >> complete(&i2c_dev->msg_complete); >> } >> goto done; >> >=20 > Please address comments in the next revision. >=20 Sorry for the delayed reply. I shared Patch V7 with above changes=20 earlier today. -regards, Bitan