[PATCH v2] i2c: at91: use dma safe buffers

[PATCH v2] i2c: at91: use dma safe buffers

[Michael Walle]

The supplied buffer might be on the stack and we get the following error
message:
[    3.312058] at91_i2c e0070600.i2c: rejecting DMA map of vmalloc memory

Use i2c_{get,put}_dma_safe_msg_buf() to get a DMA-able memory region if
necessary.

Fixes: 60937b2cdbf9 ("i2c: at91: add dma support")
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
---
changes since v1:
 - remove extra empty line
 - add fixes tag as suggested by Codrin

 drivers/i2c/busses/i2c-at91-master.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
index b0eae94909f4..5eca3b3bb609 100644
--- a/drivers/i2c/busses/i2c-at91-master.c
+++ b/drivers/i2c/busses/i2c-at91-master.c
@@ -656,6 +656,7 @@ static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
 	unsigned int_addr_flag = 0;
 	struct i2c_msg *m_start = msg;
 	bool is_read;
+	u8 *dma_buf;
 
 	dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
 
@@ -703,7 +704,17 @@ static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
 	dev->msg = m_start;
 	dev->recv_len_abort = false;
 
+	if (dev->use_dma) {
+		dma_buf = i2c_get_dma_safe_msg_buf(m_start, 1);
+		if (!dma_buf) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		dev->buf = dma_buf;
+	}
+
 	ret = at91_do_twi_transfer(dev);
+	i2c_put_dma_safe_msg_buf(dma_buf, m_start, !ret);
 
 	ret = (ret < 0) ? ret : num;
 out:
-- 
2.30.2

Re: [PATCH v2] i2c: at91: use dma safe buffers

[Michael Walle]

Am 2022-04-07 17:08, schrieb Michael Walle:
> The supplied buffer might be on the stack and we get the following 
> error
> message:
> [    3.312058] at91_i2c e0070600.i2c: rejecting DMA map of vmalloc 
> memory
> 
> Use i2c_{get,put}_dma_safe_msg_buf() to get a DMA-able memory region if
> necessary.
> 
> Fixes: 60937b2cdbf9 ("i2c: at91: add dma support")
> Signed-off-by: Michael Walle <michael@walle.cc>
> Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>

Wolfgang, will you pick this one?

-michael

Re: [PATCH v2] i2c: at91: use dma safe buffers

[Wolfram Sang]

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On Thu, Apr 07, 2022 at 05:08:28PM +0200, Michael Walle wrote:
> The supplied buffer might be on the stack and we get the following error
> message:
> [    3.312058] at91_i2c e0070600.i2c: rejecting DMA map of vmalloc memory
> 
> Use i2c_{get,put}_dma_safe_msg_buf() to get a DMA-able memory region if
> necessary.
> 
> Fixes: 60937b2cdbf9 ("i2c: at91: add dma support")
> Signed-off-by: Michael Walle <michael@walle.cc>
> Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>

Applied to for-next, thanks!

BTW, my name is Wolfram.


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Re: [PATCH v2] i2c: at91: use dma safe buffers

[Michael Walle]

Am 2022-05-04 22:23, schrieb Wolfram Sang:
> BTW, my name is Wolfram.

Sorry :/

-michael

Re: [PATCH v2] i2c: at91: use dma safe buffers

[Nathan Chancellor]

On Thu, Apr 07, 2022 at 05:08:28PM +0200, Michael Walle wrote:
> The supplied buffer might be on the stack and we get the following error
> message:
> [    3.312058] at91_i2c e0070600.i2c: rejecting DMA map of vmalloc memory
> 
> Use i2c_{get,put}_dma_safe_msg_buf() to get a DMA-able memory region if
> necessary.
> 
> Fixes: 60937b2cdbf9 ("i2c: at91: add dma support")
> Signed-off-by: Michael Walle <michael@walle.cc>
> Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
> ---
> changes since v1:
>  - remove extra empty line
>  - add fixes tag as suggested by Codrin
> 
>  drivers/i2c/busses/i2c-at91-master.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
> index b0eae94909f4..5eca3b3bb609 100644
> --- a/drivers/i2c/busses/i2c-at91-master.c
> +++ b/drivers/i2c/busses/i2c-at91-master.c
> @@ -656,6 +656,7 @@ static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
>  	unsigned int_addr_flag = 0;
>  	struct i2c_msg *m_start = msg;
>  	bool is_read;
> +	u8 *dma_buf;
>  
>  	dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
>  
> @@ -703,7 +704,17 @@ static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
>  	dev->msg = m_start;
>  	dev->recv_len_abort = false;
>  
> +	if (dev->use_dma) {
> +		dma_buf = i2c_get_dma_safe_msg_buf(m_start, 1);
> +		if (!dma_buf) {
> +			ret = -ENOMEM;
> +			goto out;
> +		}
> +		dev->buf = dma_buf;
> +	}
> +
>  	ret = at91_do_twi_transfer(dev);
> +	i2c_put_dma_safe_msg_buf(dma_buf, m_start, !ret);
>  
>  	ret = (ret < 0) ? ret : num;
>  out:
> -- 
> 2.30.2
> 
> 

This change as commit 03fbb903c8bf ("i2c: at91: use dma safe buffers")
causes the following clang warning:

drivers/i2c/busses/i2c-at91-master.c:707:6: error: variable 'dma_buf' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
        if (dev->use_dma) {
            ^~~~~~~~~~~~
drivers/i2c/busses/i2c-at91-master.c:717:27: note: uninitialized use occurs here
        i2c_put_dma_safe_msg_buf(dma_buf, m_start, !ret);
                                 ^~~~~~~
drivers/i2c/busses/i2c-at91-master.c:707:2: note: remove the 'if' if its condition is always true
        if (dev->use_dma) {
        ^~~~~~~~~~~~~~~~~~
drivers/i2c/busses/i2c-at91-master.c:659:13: note: initialize the variable 'dma_buf' to silence this warning
        u8 *dma_buf;
                   ^
                    = NULL
1 error generated.

Should this variable be initialized or should the call to
i2c_put_dma_safe_msg_buf() be moved into the if statement?

Cheers,
Nathan

Re: [PATCH v2] i2c: at91: use dma safe buffers

[Michael Walle]

[+ Wolfram]

Am 2022-05-05 16:51, schrieb Nathan Chancellor:
> On Thu, Apr 07, 2022 at 05:08:28PM +0200, Michael Walle wrote:
>> The supplied buffer might be on the stack and we get the following 
>> error
>> message:
>> [    3.312058] at91_i2c e0070600.i2c: rejecting DMA map of vmalloc 
>> memory
>> 
>> Use i2c_{get,put}_dma_safe_msg_buf() to get a DMA-able memory region 
>> if
>> necessary.
>> 
>> Fixes: 60937b2cdbf9 ("i2c: at91: add dma support")
>> Signed-off-by: Michael Walle <michael@walle.cc>
>> Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
>> ---
>> changes since v1:
>>  - remove extra empty line
>>  - add fixes tag as suggested by Codrin
>> 
>>  drivers/i2c/busses/i2c-at91-master.c | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>> 
>> diff --git a/drivers/i2c/busses/i2c-at91-master.c 
>> b/drivers/i2c/busses/i2c-at91-master.c
>> index b0eae94909f4..5eca3b3bb609 100644
>> --- a/drivers/i2c/busses/i2c-at91-master.c
>> +++ b/drivers/i2c/busses/i2c-at91-master.c
>> @@ -656,6 +656,7 @@ static int at91_twi_xfer(struct i2c_adapter *adap, 
>> struct i2c_msg *msg, int num)
>>  	unsigned int_addr_flag = 0;
>>  	struct i2c_msg *m_start = msg;
>>  	bool is_read;
>> +	u8 *dma_buf;
>> 
>>  	dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
>> 
>> @@ -703,7 +704,17 @@ static int at91_twi_xfer(struct i2c_adapter 
>> *adap, struct i2c_msg *msg, int num)
>>  	dev->msg = m_start;
>>  	dev->recv_len_abort = false;
>> 
>> +	if (dev->use_dma) {
>> +		dma_buf = i2c_get_dma_safe_msg_buf(m_start, 1);
>> +		if (!dma_buf) {
>> +			ret = -ENOMEM;
>> +			goto out;
>> +		}
>> +		dev->buf = dma_buf;
>> +	}
>> +
>>  	ret = at91_do_twi_transfer(dev);
>> +	i2c_put_dma_safe_msg_buf(dma_buf, m_start, !ret);
>> 
>>  	ret = (ret < 0) ? ret : num;
>>  out:
>> --
>> 2.30.2
>> 
>> 
> 
> This change as commit 03fbb903c8bf ("i2c: at91: use dma safe buffers")
> causes the following clang warning:

Ugh..

> drivers/i2c/busses/i2c-at91-master.c:707:6: error: variable 'dma_buf'
> is used uninitialized whenever 'if' condition is false
> [-Werror,-Wsometimes-uninitialized]
>         if (dev->use_dma) {
>             ^~~~~~~~~~~~
> drivers/i2c/busses/i2c-at91-master.c:717:27: note: uninitialized use 
> occurs here
>         i2c_put_dma_safe_msg_buf(dma_buf, m_start, !ret);
>                                  ^~~~~~~
> drivers/i2c/busses/i2c-at91-master.c:707:2: note: remove the 'if' if
> its condition is always true
>         if (dev->use_dma) {
>         ^~~~~~~~~~~~~~~~~~
> drivers/i2c/busses/i2c-at91-master.c:659:13: note: initialize the
> variable 'dma_buf' to silence this warning
>         u8 *dma_buf;
>                    ^
>                     = NULL
> 1 error generated.
> 
> Should this variable be initialized or should the call to
> i2c_put_dma_safe_msg_buf() be moved into the if statement?

Initializing dma_buf with NULL should to the trick because
i2c_put_dma_safe_msg_buf() is handling NULL gracefully. No
need for an extra "if (dma_buf)".

Will you take care or should I send a patch?

-michael

Re: [PATCH v2] i2c: at91: use dma safe buffers

[Nathan Chancellor]

On Thu, May 05, 2022 at 05:11:30PM +0200, Michael Walle wrote:
> [+ Wolfram]
> 
> Am 2022-05-05 16:51, schrieb Nathan Chancellor:
> > On Thu, Apr 07, 2022 at 05:08:28PM +0200, Michael Walle wrote:
> > > The supplied buffer might be on the stack and we get the following
> > > error
> > > message:
> > > [    3.312058] at91_i2c e0070600.i2c: rejecting DMA map of vmalloc
> > > memory
> > > 
> > > Use i2c_{get,put}_dma_safe_msg_buf() to get a DMA-able memory region
> > > if
> > > necessary.
> > > 
> > > Fixes: 60937b2cdbf9 ("i2c: at91: add dma support")
> > > Signed-off-by: Michael Walle <michael@walle.cc>
> > > Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
> > > ---
> > > changes since v1:
> > >  - remove extra empty line
> > >  - add fixes tag as suggested by Codrin
> > > 
> > >  drivers/i2c/busses/i2c-at91-master.c | 11 +++++++++++
> > >  1 file changed, 11 insertions(+)
> > > 
> > > diff --git a/drivers/i2c/busses/i2c-at91-master.c
> > > b/drivers/i2c/busses/i2c-at91-master.c
> > > index b0eae94909f4..5eca3b3bb609 100644
> > > --- a/drivers/i2c/busses/i2c-at91-master.c
> > > +++ b/drivers/i2c/busses/i2c-at91-master.c
> > > @@ -656,6 +656,7 @@ static int at91_twi_xfer(struct i2c_adapter
> > > *adap, struct i2c_msg *msg, int num)
> > >  	unsigned int_addr_flag = 0;
> > >  	struct i2c_msg *m_start = msg;
> > >  	bool is_read;
> > > +	u8 *dma_buf;
> > > 
> > >  	dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
> > > 
> > > @@ -703,7 +704,17 @@ static int at91_twi_xfer(struct i2c_adapter
> > > *adap, struct i2c_msg *msg, int num)
> > >  	dev->msg = m_start;
> > >  	dev->recv_len_abort = false;
> > > 
> > > +	if (dev->use_dma) {
> > > +		dma_buf = i2c_get_dma_safe_msg_buf(m_start, 1);
> > > +		if (!dma_buf) {
> > > +			ret = -ENOMEM;
> > > +			goto out;
> > > +		}
> > > +		dev->buf = dma_buf;
> > > +	}
> > > +
> > >  	ret = at91_do_twi_transfer(dev);
> > > +	i2c_put_dma_safe_msg_buf(dma_buf, m_start, !ret);
> > > 
> > >  	ret = (ret < 0) ? ret : num;
> > >  out:
> > > --
> > > 2.30.2
> > > 
> > > 
> > 
> > This change as commit 03fbb903c8bf ("i2c: at91: use dma safe buffers")
> > causes the following clang warning:
> 
> Ugh..
> 
> > drivers/i2c/busses/i2c-at91-master.c:707:6: error: variable 'dma_buf'
> > is used uninitialized whenever 'if' condition is false
> > [-Werror,-Wsometimes-uninitialized]
> >         if (dev->use_dma) {
> >             ^~~~~~~~~~~~
> > drivers/i2c/busses/i2c-at91-master.c:717:27: note: uninitialized use
> > occurs here
> >         i2c_put_dma_safe_msg_buf(dma_buf, m_start, !ret);
> >                                  ^~~~~~~
> > drivers/i2c/busses/i2c-at91-master.c:707:2: note: remove the 'if' if
> > its condition is always true
> >         if (dev->use_dma) {
> >         ^~~~~~~~~~~~~~~~~~
> > drivers/i2c/busses/i2c-at91-master.c:659:13: note: initialize the
> > variable 'dma_buf' to silence this warning
> >         u8 *dma_buf;
> >                    ^
> >                     = NULL
> > 1 error generated.
> > 
> > Should this variable be initialized or should the call to
> > i2c_put_dma_safe_msg_buf() be moved into the if statement?
> 
> Initializing dma_buf with NULL should to the trick because
> i2c_put_dma_safe_msg_buf() is handling NULL gracefully. No
> need for an extra "if (dma_buf)".
> 
> Will you take care or should I send a patch?

I can send a patch, thank you for the input!

Cheers,
Nathan