From: Gregor Herburger <[email protected]>
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 <[email protected]>
Signed-off-by: Matthias Schiffer <[email protected]>
---
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;
--
2.34.1
On Mon, 2023-02-20 at 16:17 +0000, Matthias Schiffer wrote:
> From: Gregor Herburger <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Matthias Schiffer <[email protected]>
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;
--
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/
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 <[email protected]>
>>
>> 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 <[email protected]>
>> Signed-off-by: Matthias Schiffer <[email protected]>
>
>
>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/
>
--
Federico Vaga - CERN BE-CEM-EDL
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