| Message ID | 20230220161628.463620-1-matthias.schiffer@ew.tq-group.com |
|---|---|
| State | New |
| Headers | show |
| Series | i2c: ocores: generate stop condition after timeout in polling mode | expand |
On Mon, 2023-02-20 at 16:17 +0000, Matthias Schiffer wrote: > From: Gregor Herburger <gregor.herburger@tq-group.com> > > In polling mode, no stop condition is generated after a timeout. This > causes SCL to remain low and thereby block the bus. If this happens > during a transfer it can cause slaves to misinterpret the subsequent > transfer and return wrong values. > > To solve this, pass the ETIMEDOUT error up from ocores_process_polling() > instead of setting STATE_ERROR directly. The caller is adjusted to call > ocores_process_timeout() on error both in polling and in IRQ mode, which > will set STATE_ERROR and generate a stop condition. > > Fixes: 69c8c0c0efa8 ("i2c: ocores: add polling interface") > Signed-off-by: Gregor Herburger <gregor.herburger@tq-group.com> > Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com> Any chance we can get someone to have a look at this patch? Regards, Matthias > --- > drivers/i2c/busses/i2c-ocores.c | 28 +++++++++++++++------------- > 1 file changed, 15 insertions(+), 13 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c > index a0af027db04c1..28bcda3f7040a 100644 > --- a/drivers/i2c/busses/i2c-ocores.c > +++ b/drivers/i2c/busses/i2c-ocores.c > @@ -342,18 +342,18 @@ static int ocores_poll_wait(struct ocores_i2c *i2c) > * ocores_isr(), we just add our polling code around it. > * > * It can run in atomic context > + * > + * Return: 0 on success, -ETIMEDOUT on timeout > */ > -static void ocores_process_polling(struct ocores_i2c *i2c) > +static int ocores_process_polling(struct ocores_i2c *i2c) > { > while (1) { > irqreturn_t ret; > int err; > > err = ocores_poll_wait(i2c); > - if (err) { > - i2c->state = STATE_ERROR; > - break; /* timeout */ > - } > + if (err) > + return err; > > ret = ocores_isr(-1, i2c); > if (ret == IRQ_NONE) > @@ -364,6 +364,8 @@ static void ocores_process_polling(struct ocores_i2c *i2c) > break; > } > } > + > + return 0; > } > > static int ocores_xfer_core(struct ocores_i2c *i2c, > @@ -387,16 +389,16 @@ static int ocores_xfer_core(struct ocores_i2c *i2c, > oc_setreg(i2c, OCI2C_DATA, i2c_8bit_addr_from_msg(i2c->msg)); > oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START); > > - if (polling) { > - ocores_process_polling(i2c); > - } else { > + if (polling) > + ret = ocores_process_polling(i2c); > + else > ret = wait_event_timeout(i2c->wait, > (i2c->state == STATE_ERROR) || > - (i2c->state == STATE_DONE), HZ); > - if (ret == 0) { > - ocores_process_timeout(i2c); > - return -ETIMEDOUT; > - } > + (i2c->state == STATE_DONE), HZ) ? > + 0 : -ETIMEDOUT; > + if (ret) { > + ocores_process_timeout(i2c); > + return ret; > } > > return (i2c->state == STATE_DONE) ? num : -EIO;
On Wed, Apr 12, 2023 at 11:49:32AM +0200, Matthias Schiffer wrote: >On Mon, 2023-02-20 at 16:17 +0000, Matthias Schiffer wrote: >> From: Gregor Herburger <gregor.herburger@tq-group.com> >> >> In polling mode, no stop condition is generated after a timeout. This >> causes SCL to remain low and thereby block the bus. If this happens >> during a transfer it can cause slaves to misinterpret the subsequent >> transfer and return wrong values. >> >> To solve this, pass the ETIMEDOUT error up from ocores_process_polling() >> instead of setting STATE_ERROR directly. The caller is adjusted to call >> ocores_process_timeout() on error both in polling and in IRQ mode, which >> will set STATE_ERROR and generate a stop condition. I can see and confirm the bug. The patch seems fine to me, but I do not have the hardware at hand right now for a real test. Following a few cosmetic comments. >> Fixes: 69c8c0c0efa8 ("i2c: ocores: add polling interface") >> Signed-off-by: Gregor Herburger <gregor.herburger@tq-group.com> >> Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com> > > >Any chance we can get someone to have a look at this patch? > >Regards, >Matthias > > > >> --- >> drivers/i2c/busses/i2c-ocores.c | 28 +++++++++++++++------------- >> 1 file changed, 15 insertions(+), 13 deletions(-) >> >> diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c >> index a0af027db04c1..28bcda3f7040a 100644 >> --- a/drivers/i2c/busses/i2c-ocores.c >> +++ b/drivers/i2c/busses/i2c-ocores.c >> @@ -342,18 +342,18 @@ static int ocores_poll_wait(struct ocores_i2c *i2c) >> * ocores_isr(), we just add our polling code around it. >> * >> * It can run in atomic context >> + * >> + * Return: 0 on success, -ETIMEDOUT on timeout >> */ >> -static void ocores_process_polling(struct ocores_i2c *i2c) >> +static int ocores_process_polling(struct ocores_i2c *i2c) >> { >> while (1) { >> irqreturn_t ret; >> int err; >> >> err = ocores_poll_wait(i2c); >> - if (err) { >> - i2c->state = STATE_ERROR; >> - break; /* timeout */ >> - } >> + if (err) >> + return err; >> >> ret = ocores_isr(-1, i2c); >> if (ret == IRQ_NONE) >> @@ -364,6 +364,8 @@ static void ocores_process_polling(struct ocores_i2c *i2c) >> break; >> } >> } >> + >> + return 0; >> } I would try to have a single return point at the end `return err` and inside the loop just a break. >> >> static int ocores_xfer_core(struct ocores_i2c *i2c, >> @@ -387,16 +389,16 @@ static int ocores_xfer_core(struct ocores_i2c *i2c, >> oc_setreg(i2c, OCI2C_DATA, i2c_8bit_addr_from_msg(i2c->msg)); >> oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START); >> >> - if (polling) { >> - ocores_process_polling(i2c); >> - } else { >> + if (polling) >> + ret = ocores_process_polling(i2c); >> + else >> ret = wait_event_timeout(i2c->wait, >> (i2c->state == STATE_ERROR) || >> - (i2c->state == STATE_DONE), HZ); >> - if (ret == 0) { >> - ocores_process_timeout(i2c); >> - return -ETIMEDOUT; >> - } >> + (i2c->state == STATE_DONE), HZ) ? >> + 0 : -ETIMEDOUT; For readability, I would avoid the ternary operator here and do the assignement with an `if` as it was before. if (ret == 0) ret = -ETIMEDOUT; >> + if (ret) { >> + ocores_process_timeout(i2c); >> + return ret; >> } >> >> return (i2c->state == STATE_DONE) ? num : -EIO; > >-- >TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany >Amtsgericht München, HRB 105018 >Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider >http://www.tq-group.com/ >
Hi Matthias I also don't have access to the hardware, but the change looks O.K. > static int ocores_xfer_core(struct ocores_i2c *i2c, > @@ -387,16 +389,16 @@ static int ocores_xfer_core(struct ocores_i2c *i2c, > oc_setreg(i2c, OCI2C_DATA, i2c_8bit_addr_from_msg(i2c->msg)); > oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START); > > - if (polling) { > - ocores_process_polling(i2c); > - } else { > + if (polling) > + ret = ocores_process_polling(i2c); > + else > ret = wait_event_timeout(i2c->wait, > (i2c->state == STATE_ERROR) || > - (i2c->state == STATE_DONE), HZ); > - if (ret == 0) { > - ocores_process_timeout(i2c); > - return -ETIMEDOUT; > - } > + (i2c->state == STATE_DONE), HZ) ? > + 0 : -ETIMEDOUT; > + if (ret) { > + ocores_process_timeout(i2c); > + return ret; > } The ret == 0 becoming ret is not so obvious. Rather than having the trinary, do if (ret == 0) ret = -ETIMEDOUT; and then fall into your new if clause. I think that makes it more obvious that wait_event_timeout() returns 0 on timeout. Andrew
diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c index a0af027db04c1..28bcda3f7040a 100644 --- a/drivers/i2c/busses/i2c-ocores.c +++ b/drivers/i2c/busses/i2c-ocores.c @@ -342,18 +342,18 @@ static int ocores_poll_wait(struct ocores_i2c *i2c) * ocores_isr(), we just add our polling code around it. * * It can run in atomic context + * + * Return: 0 on success, -ETIMEDOUT on timeout */ -static void ocores_process_polling(struct ocores_i2c *i2c) +static int ocores_process_polling(struct ocores_i2c *i2c) { while (1) { irqreturn_t ret; int err; err = ocores_poll_wait(i2c); - if (err) { - i2c->state = STATE_ERROR; - break; /* timeout */ - } + if (err) + return err; ret = ocores_isr(-1, i2c); if (ret == IRQ_NONE) @@ -364,6 +364,8 @@ static void ocores_process_polling(struct ocores_i2c *i2c) break; } } + + return 0; } static int ocores_xfer_core(struct ocores_i2c *i2c, @@ -387,16 +389,16 @@ static int ocores_xfer_core(struct ocores_i2c *i2c, oc_setreg(i2c, OCI2C_DATA, i2c_8bit_addr_from_msg(i2c->msg)); oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START); - if (polling) { - ocores_process_polling(i2c); - } else { + if (polling) + ret = ocores_process_polling(i2c); + else ret = wait_event_timeout(i2c->wait, (i2c->state == STATE_ERROR) || - (i2c->state == STATE_DONE), HZ); - if (ret == 0) { - ocores_process_timeout(i2c); - return -ETIMEDOUT; - } + (i2c->state == STATE_DONE), HZ) ? + 0 : -ETIMEDOUT; + if (ret) { + ocores_process_timeout(i2c); + return ret; } return (i2c->state == STATE_DONE) ? num : -EIO;