[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Gustavo A. R. Silva]

Add suffix ULL to constant 9 in order to give the compiler complete
information about the proper arithmetic to use. Notice that this
constant is used in a context that expects an expression of type
unsigned long long (64 bits, unsigned).

The expression tfr->len * 9 * 1000000 is currently being evaluated
using 32-bit arithmetic.

Addresses-Coverity-ID: 1339619
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/spi/spi-bcm2835aux.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index 7428091..a768c23 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -363,7 +363,7 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 	 * chunk getting transferred - in our case the chunk size
 	 * is 3 bytes, so we approximate this by 9 bits/byte
 	 */
-	xfer_time_us = tfr->len * 9 * 1000000;
+	xfer_time_us = tfr->len * 9ULL * 1000000;
 	do_div(xfer_time_us, spi_used_hz);
 
 	/* run in polling mode for short transfers */
-- 
2.7.4

[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Gustavo A. R. Silva]

Add suffix ULL to constant 9 in order to give the compiler complete
information about the proper arithmetic to use. Notice that this
constant is used in a context that expects an expression of type
unsigned long long (64 bits, unsigned).

The expression tfr->len * 9 * 1000000 is currently being evaluated
using 32-bit arithmetic.

Addresses-Coverity-ID: 1339619
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/spi/spi-bcm2835aux.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index 7428091..a768c23 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -363,7 +363,7 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 	 * chunk getting transferred - in our case the chunk size
 	 * is 3 bytes, so we approximate this by 9 bits/byte
 	 */
-	xfer_time_us = tfr->len * 9 * 1000000;
+	xfer_time_us = tfr->len * 9ULL * 1000000;
 	do_div(xfer_time_us, spi_used_hz);
 
 	/* run in polling mode for short transfers */
-- 
2.7.4

Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Eric Anholt]

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"Gustavo A. R. Silva" <gustavo@embeddedor.com> writes:

> Add suffix ULL to constant 9 in order to give the compiler complete
> information about the proper arithmetic to use. Notice that this
> constant is used in a context that expects an expression of type
> unsigned long long (64 bits, unsigned).
>
> The expression tfr->len * 9 * 1000000 is currently being evaluated
> using 32-bit arithmetic.
>
> Addresses-Coverity-ID: 1339619
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

The effect looks like it would be that we would have chosen polling mode
instead of waiting for interrupts for some transfers >477 seconds.
Seems like a good fix for an unlikely bug.

Reviewed-by: Eric Anholt <eric@anholt.net>

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[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Eric Anholt]

"Gustavo A. R. Silva" <gustavo@embeddedor.com> writes:

> Add suffix ULL to constant 9 in order to give the compiler complete
> information about the proper arithmetic to use. Notice that this
> constant is used in a context that expects an expression of type
> unsigned long long (64 bits, unsigned).
>
> The expression tfr->len * 9 * 1000000 is currently being evaluated
> using 32-bit arithmetic.
>
> Addresses-Coverity-ID: 1339619
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

The effect looks like it would be that we would have chosen polling mode
instead of waiting for interrupts for some transfers >477 seconds.
Seems like a good fix for an unlikely bug.

Reviewed-by: Eric Anholt <eric@anholt.net>
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Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Gustavo A. R. Silva]

Hi Eric,

On 02/08/2018 02:22 AM, Eric Anholt wrote:
> "Gustavo A. R. Silva" <gustavo@embeddedor.com> writes:
> 
>> Add suffix ULL to constant 9 in order to give the compiler complete
>> information about the proper arithmetic to use. Notice that this
>> constant is used in a context that expects an expression of type
>> unsigned long long (64 bits, unsigned).
>>
>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>> using 32-bit arithmetic.
>>
>> Addresses-Coverity-ID: 1339619
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> 
> The effect looks like it would be that we would have chosen polling mode
> instead of waiting for interrupts for some transfers >477 seconds.
> Seems like a good fix for an unlikely bug.
> 
> Reviewed-by: Eric Anholt <eric@anholt.net>
> 

Thank you for your review.

--
Gustavo

[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Gustavo A. R. Silva]

Hi Eric,

On 02/08/2018 02:22 AM, Eric Anholt wrote:
> "Gustavo A. R. Silva" <gustavo@embeddedor.com> writes:
> 
>> Add suffix ULL to constant 9 in order to give the compiler complete
>> information about the proper arithmetic to use. Notice that this
>> constant is used in a context that expects an expression of type
>> unsigned long long (64 bits, unsigned).
>>
>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>> using 32-bit arithmetic.
>>
>> Addresses-Coverity-ID: 1339619
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> 
> The effect looks like it would be that we would have chosen polling mode
> instead of waiting for interrupts for some transfers >477 seconds.
> Seems like a good fix for an unlikely bug.
> 
> Reviewed-by: Eric Anholt <eric@anholt.net>
> 

Thank you for your review.

--
Gustavo

Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Ard Biesheuvel]

On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com> wrote:
> Add suffix ULL to constant 9 in order to give the compiler complete
> information about the proper arithmetic to use. Notice that this
> constant is used in a context that expects an expression of type
> unsigned long long (64 bits, unsigned).
>
> The expression tfr->len * 9 * 1000000 is currently being evaluated
> using 32-bit arithmetic.
>
> Addresses-Coverity-ID: 1339619

What does this number mean? If it is an index into some internal
database, please remove it.

> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/spi/spi-bcm2835aux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
> index 7428091..a768c23 100644
> --- a/drivers/spi/spi-bcm2835aux.c
> +++ b/drivers/spi/spi-bcm2835aux.c
> @@ -363,7 +363,7 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
>          * chunk getting transferred - in our case the chunk size
>          * is 3 bytes, so we approximate this by 9 bits/byte
>          */
> -       xfer_time_us = tfr->len * 9 * 1000000;
> +       xfer_time_us = tfr->len * 9ULL * 1000000;
>         do_div(xfer_time_us, spi_used_hz);
>
>         /* run in polling mode for short transfers */
> --
> 2.7.4
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Ard Biesheuvel]

On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com> wrote:
> Add suffix ULL to constant 9 in order to give the compiler complete
> information about the proper arithmetic to use. Notice that this
> constant is used in a context that expects an expression of type
> unsigned long long (64 bits, unsigned).
>
> The expression tfr->len * 9 * 1000000 is currently being evaluated
> using 32-bit arithmetic.
>
> Addresses-Coverity-ID: 1339619

What does this number mean? If it is an index into some internal
database, please remove it.

> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/spi/spi-bcm2835aux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
> index 7428091..a768c23 100644
> --- a/drivers/spi/spi-bcm2835aux.c
> +++ b/drivers/spi/spi-bcm2835aux.c
> @@ -363,7 +363,7 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
>          * chunk getting transferred - in our case the chunk size
>          * is 3 bytes, so we approximate this by 9 bits/byte
>          */
> -       xfer_time_us = tfr->len * 9 * 1000000;
> +       xfer_time_us = tfr->len * 9ULL * 1000000;
>         do_div(xfer_time_us, spi_used_hz);
>
>         /* run in polling mode for short transfers */
> --
> 2.7.4
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Ard Biesheuvel]

On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com> wrote:
> Add suffix ULL to constant 9 in order to give the compiler complete
> information about the proper arithmetic to use. Notice that this
> constant is used in a context that expects an expression of type
> unsigned long long (64 bits, unsigned).
>
> The expression tfr->len * 9 * 1000000 is currently being evaluated
> using 32-bit arithmetic.
>
> Addresses-Coverity-ID: 1339619

What does this number mean? If it is an index into some internal
database, please remove it.

> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/spi/spi-bcm2835aux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
> index 7428091..a768c23 100644
> --- a/drivers/spi/spi-bcm2835aux.c
> +++ b/drivers/spi/spi-bcm2835aux.c
> @@ -363,7 +363,7 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
>          * chunk getting transferred - in our case the chunk size
>          * is 3 bytes, so we approximate this by 9 bits/byte
>          */
> -       xfer_time_us = tfr->len * 9 * 1000000;
> +       xfer_time_us = tfr->len * 9ULL * 1000000;
>         do_div(xfer_time_us, spi_used_hz);
>
>         /* run in polling mode for short transfers */
> --
> 2.7.4
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Gustavo A. R. Silva]

Hi Ard,

On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com> wrote:
>> Add suffix ULL to constant 9 in order to give the compiler complete
>> information about the proper arithmetic to use. Notice that this
>> constant is used in a context that expects an expression of type
>> unsigned long long (64 bits, unsigned).
>>
>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>> using 32-bit arithmetic.
>>
>> Addresses-Coverity-ID: 1339619
> 
> What does this number mean? If it is an index into some internal
> database, please remove it.
> 

This is a unique Coverity identifier. We want to keep information like 
public Bugzilla IDs and tools like Coverity on the commit message.

Thanks
--
Gustavo

[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Gustavo A. R. Silva]

Hi Ard,

On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com> wrote:
>> Add suffix ULL to constant 9 in order to give the compiler complete
>> information about the proper arithmetic to use. Notice that this
>> constant is used in a context that expects an expression of type
>> unsigned long long (64 bits, unsigned).
>>
>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>> using 32-bit arithmetic.
>>
>> Addresses-Coverity-ID: 1339619
> 
> What does this number mean? If it is an index into some internal
> database, please remove it.
> 

This is a unique Coverity identifier. We want to keep information like 
public Bugzilla IDs and tools like Coverity on the commit message.

Thanks
--
Gustavo

Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Ard Biesheuvel]

On 12 February 2018 at 18:04, Gustavo A. R. Silva
<garsilva@embeddedor.com> wrote:
> Hi Ard,
>
> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>
>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com>
>> wrote:
>>>
>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>> information about the proper arithmetic to use. Notice that this
>>> constant is used in a context that expects an expression of type
>>> unsigned long long (64 bits, unsigned).
>>>
>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>> using 32-bit arithmetic.
>>>
>>> Addresses-Coverity-ID: 1339619
>>
>>
>> What does this number mean? If it is an index into some internal
>> database, please remove it.
>>
>
> This is a unique Coverity identifier. We want to keep information like
> public Bugzilla IDs and tools like Coverity on the commit message.
>

Who is 'we' in this case? And how is this id to any benefit of other
people that have been excluded from 'we'?

If you add identifiers like this, make sure that they don't only make
sense to the in-crowd. For instance, you could replace this with a
http link to the database entry if you really must.

[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Ard Biesheuvel]

On 12 February 2018 at 18:04, Gustavo A. R. Silva
<garsilva@embeddedor.com> wrote:
> Hi Ard,
>
> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>
>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com>
>> wrote:
>>>
>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>> information about the proper arithmetic to use. Notice that this
>>> constant is used in a context that expects an expression of type
>>> unsigned long long (64 bits, unsigned).
>>>
>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>> using 32-bit arithmetic.
>>>
>>> Addresses-Coverity-ID: 1339619
>>
>>
>> What does this number mean? If it is an index into some internal
>> database, please remove it.
>>
>
> This is a unique Coverity identifier. We want to keep information like
> public Bugzilla IDs and tools like Coverity on the commit message.
>

Who is 'we' in this case? And how is this id to any benefit of other
people that have been excluded from 'we'?

If you add identifiers like this, make sure that they don't only make
sense to the in-crowd. For instance, you could replace this with a
http link to the database entry if you really must.

Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Florian Fainelli]

On 02/12/2018 10:45 AM, Ard Biesheuvel wrote:
> On 12 February 2018 at 18:04, Gustavo A. R. Silva
> <garsilva@embeddedor.com> wrote:
>> Hi Ard,
>>
>> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>>
>>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com>
>>> wrote:
>>>>
>>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>>> information about the proper arithmetic to use. Notice that this
>>>> constant is used in a context that expects an expression of type
>>>> unsigned long long (64 bits, unsigned).
>>>>
>>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>>> using 32-bit arithmetic.
>>>>
>>>> Addresses-Coverity-ID: 1339619
>>>
>>>
>>> What does this number mean? If it is an index into some internal
>>> database, please remove it.
>>>
>>
>> This is a unique Coverity identifier. We want to keep information like
>> public Bugzilla IDs and tools like Coverity on the commit message.
>>
> 
> Who is 'we' in this case? And how is this id to any benefit of other
> people that have been excluded from 'we'?

We is probably the greater Linux community here.

> 
> If you add identifiers like this, make sure that they don't only make
> sense to the in-crowd. For instance, you could replace this with a
> http link to the database entry if you really must.

I don't think it is that easy to extract good URLs from the public Linux
coverity instance which is why referring to coverity IDs is being done
AFAICT.
-- 
Florian

[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Florian Fainelli]

On 02/12/2018 10:45 AM, Ard Biesheuvel wrote:
> On 12 February 2018 at 18:04, Gustavo A. R. Silva
> <garsilva@embeddedor.com> wrote:
>> Hi Ard,
>>
>> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>>
>>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com>
>>> wrote:
>>>>
>>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>>> information about the proper arithmetic to use. Notice that this
>>>> constant is used in a context that expects an expression of type
>>>> unsigned long long (64 bits, unsigned).
>>>>
>>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>>> using 32-bit arithmetic.
>>>>
>>>> Addresses-Coverity-ID: 1339619
>>>
>>>
>>> What does this number mean? If it is an index into some internal
>>> database, please remove it.
>>>
>>
>> This is a unique Coverity identifier. We want to keep information like
>> public Bugzilla IDs and tools like Coverity on the commit message.
>>
> 
> Who is 'we' in this case? And how is this id to any benefit of other
> people that have been excluded from 'we'?

We is probably the greater Linux community here.

> 
> If you add identifiers like this, make sure that they don't only make
> sense to the in-crowd. For instance, you could replace this with a
> http link to the database entry if you really must.

I don't think it is that easy to extract good URLs from the public Linux
coverity instance which is why referring to coverity IDs is being done
AFAICT.
-- 
Florian

Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Florian Fainelli]

On 02/12/2018 10:45 AM, Ard Biesheuvel wrote:
> On 12 February 2018 at 18:04, Gustavo A. R. Silva
> <garsilva-L1vi/lXTdts+Va1GwOuvDg@public.gmane.org> wrote:
>> Hi Ard,
>>
>> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>>
>>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo-L1vi/lXTdts+Va1GwOuvDg@public.gmane.org>
>>> wrote:
>>>>
>>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>>> information about the proper arithmetic to use. Notice that this
>>>> constant is used in a context that expects an expression of type
>>>> unsigned long long (64 bits, unsigned).
>>>>
>>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>>> using 32-bit arithmetic.
>>>>
>>>> Addresses-Coverity-ID: 1339619
>>>
>>>
>>> What does this number mean? If it is an index into some internal
>>> database, please remove it.
>>>
>>
>> This is a unique Coverity identifier. We want to keep information like
>> public Bugzilla IDs and tools like Coverity on the commit message.
>>
> 
> Who is 'we' in this case? And how is this id to any benefit of other
> people that have been excluded from 'we'?

We is probably the greater Linux community here.

> 
> If you add identifiers like this, make sure that they don't only make
> sense to the in-crowd. For instance, you could replace this with a
> http link to the database entry if you really must.

I don't think it is that easy to extract good URLs from the public Linux
coverity instance which is why referring to coverity IDs is being done
AFAICT.
-- 
Florian
--
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Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Ard Biesheuvel]

On 12 February 2018 at 19:10, Florian Fainelli <f.fainelli@gmail.com> wrote:
> On 02/12/2018 10:45 AM, Ard Biesheuvel wrote:
>> On 12 February 2018 at 18:04, Gustavo A. R. Silva
>> <garsilva@embeddedor.com> wrote:
>>> Hi Ard,
>>>
>>> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>>>
>>>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com>
>>>> wrote:
>>>>>
>>>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>>>> information about the proper arithmetic to use. Notice that this
>>>>> constant is used in a context that expects an expression of type
>>>>> unsigned long long (64 bits, unsigned).
>>>>>
>>>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>>>> using 32-bit arithmetic.
>>>>>
>>>>> Addresses-Coverity-ID: 1339619
>>>>
>>>>
>>>> What does this number mean? If it is an index into some internal
>>>> database, please remove it.
>>>>
>>>
>>> This is a unique Coverity identifier. We want to keep information like
>>> public Bugzilla IDs and tools like Coverity on the commit message.
>>>
>>
>> Who is 'we' in this case? And how is this id to any benefit of other
>> people that have been excluded from 'we'?
>
> We is probably the greater Linux community here.
>
>>
>> If you add identifiers like this, make sure that they don't only make
>> sense to the in-crowd. For instance, you could replace this with a
>> http link to the database entry if you really must.
>
> I don't think it is that easy to extract good URLs from the public Linux
> coverity instance which is why referring to coverity IDs is being done
> AFAICT.

Ah ok, pardon my ignorance then. I wasn't aware there is a public
Linux coverity instance. Got a link?

[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Ard Biesheuvel]

On 12 February 2018 at 19:10, Florian Fainelli <f.fainelli@gmail.com> wrote:
> On 02/12/2018 10:45 AM, Ard Biesheuvel wrote:
>> On 12 February 2018 at 18:04, Gustavo A. R. Silva
>> <garsilva@embeddedor.com> wrote:
>>> Hi Ard,
>>>
>>> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>>>
>>>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com>
>>>> wrote:
>>>>>
>>>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>>>> information about the proper arithmetic to use. Notice that this
>>>>> constant is used in a context that expects an expression of type
>>>>> unsigned long long (64 bits, unsigned).
>>>>>
>>>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>>>> using 32-bit arithmetic.
>>>>>
>>>>> Addresses-Coverity-ID: 1339619
>>>>
>>>>
>>>> What does this number mean? If it is an index into some internal
>>>> database, please remove it.
>>>>
>>>
>>> This is a unique Coverity identifier. We want to keep information like
>>> public Bugzilla IDs and tools like Coverity on the commit message.
>>>
>>
>> Who is 'we' in this case? And how is this id to any benefit of other
>> people that have been excluded from 'we'?
>
> We is probably the greater Linux community here.
>
>>
>> If you add identifiers like this, make sure that they don't only make
>> sense to the in-crowd. For instance, you could replace this with a
>> http link to the database entry if you really must.
>
> I don't think it is that easy to extract good URLs from the public Linux
> coverity instance which is why referring to coverity IDs is being done
> AFAICT.

Ah ok, pardon my ignorance then. I wasn't aware there is a public
Linux coverity instance. Got a link?

Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Ard Biesheuvel]

On 12 February 2018 at 19:10, Florian Fainelli <f.fainelli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> On 02/12/2018 10:45 AM, Ard Biesheuvel wrote:
>> On 12 February 2018 at 18:04, Gustavo A. R. Silva
>> <garsilva-L1vi/lXTdts+Va1GwOuvDg@public.gmane.org> wrote:
>>> Hi Ard,
>>>
>>> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>>>
>>>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo-L1vi/lXTdts+Va1GwOuvDg@public.gmane.org>
>>>> wrote:
>>>>>
>>>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>>>> information about the proper arithmetic to use. Notice that this
>>>>> constant is used in a context that expects an expression of type
>>>>> unsigned long long (64 bits, unsigned).
>>>>>
>>>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>>>> using 32-bit arithmetic.
>>>>>
>>>>> Addresses-Coverity-ID: 1339619
>>>>
>>>>
>>>> What does this number mean? If it is an index into some internal
>>>> database, please remove it.
>>>>
>>>
>>> This is a unique Coverity identifier. We want to keep information like
>>> public Bugzilla IDs and tools like Coverity on the commit message.
>>>
>>
>> Who is 'we' in this case? And how is this id to any benefit of other
>> people that have been excluded from 'we'?
>
> We is probably the greater Linux community here.
>
>>
>> If you add identifiers like this, make sure that they don't only make
>> sense to the in-crowd. For instance, you could replace this with a
>> http link to the database entry if you really must.
>
> I don't think it is that easy to extract good URLs from the public Linux
> coverity instance which is why referring to coverity IDs is being done
> AFAICT.

Ah ok, pardon my ignorance then. I wasn't aware there is a public
Linux coverity instance. Got a link?
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Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Florian Fainelli]

On 02/12/2018 11:11 AM, Ard Biesheuvel wrote:
> On 12 February 2018 at 19:10, Florian Fainelli <f.fainelli@gmail.com> wrote:
>> On 02/12/2018 10:45 AM, Ard Biesheuvel wrote:
>>> On 12 February 2018 at 18:04, Gustavo A. R. Silva
>>> <garsilva@embeddedor.com> wrote:
>>>> Hi Ard,
>>>>
>>>> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>>>>
>>>>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com>
>>>>> wrote:
>>>>>>
>>>>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>>>>> information about the proper arithmetic to use. Notice that this
>>>>>> constant is used in a context that expects an expression of type
>>>>>> unsigned long long (64 bits, unsigned).
>>>>>>
>>>>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>>>>> using 32-bit arithmetic.
>>>>>>
>>>>>> Addresses-Coverity-ID: 1339619
>>>>>
>>>>>
>>>>> What does this number mean? If it is an index into some internal
>>>>> database, please remove it.
>>>>>
>>>>
>>>> This is a unique Coverity identifier. We want to keep information like
>>>> public Bugzilla IDs and tools like Coverity on the commit message.
>>>>
>>>
>>> Who is 'we' in this case? And how is this id to any benefit of other
>>> people that have been excluded from 'we'?
>>
>> We is probably the greater Linux community here.
>>
>>>
>>> If you add identifiers like this, make sure that they don't only make
>>> sense to the in-crowd. For instance, you could replace this with a
>>> http link to the database entry if you really must.
>>
>> I don't think it is that easy to extract good URLs from the public Linux
>> coverity instance which is why referring to coverity IDs is being done
>> AFAICT.
> 
> Ah ok, pardon my ignorance then. I wasn't aware there is a public
> Linux coverity instance. Got a link?

It requires you to sign up to get notifications and have a dashboard,
does this link work for you?

https://scan.coverity.com/projects/linux?tab=overview
-- 
Florian

[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Florian Fainelli]

On 02/12/2018 11:11 AM, Ard Biesheuvel wrote:
> On 12 February 2018 at 19:10, Florian Fainelli <f.fainelli@gmail.com> wrote:
>> On 02/12/2018 10:45 AM, Ard Biesheuvel wrote:
>>> On 12 February 2018 at 18:04, Gustavo A. R. Silva
>>> <garsilva@embeddedor.com> wrote:
>>>> Hi Ard,
>>>>
>>>> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>>>>
>>>>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo@embeddedor.com>
>>>>> wrote:
>>>>>>
>>>>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>>>>> information about the proper arithmetic to use. Notice that this
>>>>>> constant is used in a context that expects an expression of type
>>>>>> unsigned long long (64 bits, unsigned).
>>>>>>
>>>>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>>>>> using 32-bit arithmetic.
>>>>>>
>>>>>> Addresses-Coverity-ID: 1339619
>>>>>
>>>>>
>>>>> What does this number mean? If it is an index into some internal
>>>>> database, please remove it.
>>>>>
>>>>
>>>> This is a unique Coverity identifier. We want to keep information like
>>>> public Bugzilla IDs and tools like Coverity on the commit message.
>>>>
>>>
>>> Who is 'we' in this case? And how is this id to any benefit of other
>>> people that have been excluded from 'we'?
>>
>> We is probably the greater Linux community here.
>>
>>>
>>> If you add identifiers like this, make sure that they don't only make
>>> sense to the in-crowd. For instance, you could replace this with a
>>> http link to the database entry if you really must.
>>
>> I don't think it is that easy to extract good URLs from the public Linux
>> coverity instance which is why referring to coverity IDs is being done
>> AFAICT.
> 
> Ah ok, pardon my ignorance then. I wasn't aware there is a public
> Linux coverity instance. Got a link?

It requires you to sign up to get notifications and have a dashboard,
does this link work for you?

https://scan.coverity.com/projects/linux?tab=overview
-- 
Florian

Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Florian Fainelli]

On 02/12/2018 11:11 AM, Ard Biesheuvel wrote:
> On 12 February 2018 at 19:10, Florian Fainelli <f.fainelli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> On 02/12/2018 10:45 AM, Ard Biesheuvel wrote:
>>> On 12 February 2018 at 18:04, Gustavo A. R. Silva
>>> <garsilva-L1vi/lXTdts+Va1GwOuvDg@public.gmane.org> wrote:
>>>> Hi Ard,
>>>>
>>>> On 02/08/2018 03:54 AM, Ard Biesheuvel wrote:
>>>>>
>>>>> On 7 February 2018 at 16:00, Gustavo A. R. Silva <gustavo-L1vi/lXTdts+Va1GwOuvDg@public.gmane.org>
>>>>> wrote:
>>>>>>
>>>>>> Add suffix ULL to constant 9 in order to give the compiler complete
>>>>>> information about the proper arithmetic to use. Notice that this
>>>>>> constant is used in a context that expects an expression of type
>>>>>> unsigned long long (64 bits, unsigned).
>>>>>>
>>>>>> The expression tfr->len * 9 * 1000000 is currently being evaluated
>>>>>> using 32-bit arithmetic.
>>>>>>
>>>>>> Addresses-Coverity-ID: 1339619
>>>>>
>>>>>
>>>>> What does this number mean? If it is an index into some internal
>>>>> database, please remove it.
>>>>>
>>>>
>>>> This is a unique Coverity identifier. We want to keep information like
>>>> public Bugzilla IDs and tools like Coverity on the commit message.
>>>>
>>>
>>> Who is 'we' in this case? And how is this id to any benefit of other
>>> people that have been excluded from 'we'?
>>
>> We is probably the greater Linux community here.
>>
>>>
>>> If you add identifiers like this, make sure that they don't only make
>>> sense to the in-crowd. For instance, you could replace this with a
>>> http link to the database entry if you really must.
>>
>> I don't think it is that easy to extract good URLs from the public Linux
>> coverity instance which is why referring to coverity IDs is being done
>> AFAICT.
> 
> Ah ok, pardon my ignorance then. I wasn't aware there is a public
> Linux coverity instance. Got a link?

It requires you to sign up to get notifications and have a dashboard,
does this link work for you?

https://scan.coverity.com/projects/linux?tab=overview
-- 
Florian
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Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Trent Piepho]

On Wed, 2018-02-07 at 10:00 -0600, Gustavo A. R. Silva wrote:
> Add suffix ULL to constant 9 in order to give the compiler complete
> information about the proper arithmetic to use. Notice that this
> constant is used in a context that expects an expression of type
> unsigned long long (64 bits, unsigned).
> 
> The expression tfr->len * 9 * 1000000 is currently being evaluated
> using 32-bit arithmetic.
> 
> Addresses-Coverity-ID: 1339619
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/spi/spi-bcm2835aux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
> index 7428091..a768c23 100644
> --- a/drivers/spi/spi-bcm2835aux.c
> +++ b/drivers/spi/spi-bcm2835aux.c
> @@ -363,7 +363,7 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
>  	 * chunk getting transferred - in our case the chunk size
>  	 * is 3 bytes, so we approximate this by 9 bits/byte
>  	 */
> -	xfer_time_us = tfr->len * 9 * 1000000;
> +	xfer_time_us = tfr->len * 9ULL * 1000000;
>  	do_div(xfer_time_us, spi_used_hz);
>  
>  	/* run in polling mode for short transfers */
	if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US)

If one looks at the logic as a whole...

tfr->len * 9ULL * 100000 / spi_used_hz < 30

A little algebra can change that into:

tfr->len < spi_used_hz / 300000

So rather than add more 64-bit math, it can be removed entirely.  Both
the length and speed are 32 bits and there's no need to multiply them
into something larger than might need 64 bits.

[PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Trent Piepho]

On Wed, 2018-02-07 at 10:00 -0600, Gustavo A. R. Silva wrote:
> Add suffix ULL to constant 9 in order to give the compiler complete
> information about the proper arithmetic to use. Notice that this
> constant is used in a context that expects an expression of type
> unsigned long long (64 bits, unsigned).
> 
> The expression tfr->len * 9 * 1000000 is currently being evaluated
> using 32-bit arithmetic.
> 
> Addresses-Coverity-ID: 1339619
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/spi/spi-bcm2835aux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
> index 7428091..a768c23 100644
> --- a/drivers/spi/spi-bcm2835aux.c
> +++ b/drivers/spi/spi-bcm2835aux.c
> @@ -363,7 +363,7 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
>  	 * chunk getting transferred - in our case the chunk size
>  	 * is 3 bytes, so we approximate this by 9 bits/byte
>  	 */
> -	xfer_time_us = tfr->len * 9 * 1000000;
> +	xfer_time_us = tfr->len * 9ULL * 1000000;
>  	do_div(xfer_time_us, spi_used_hz);
>  
>  	/* run in polling mode for short transfers */
	if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US)

If one looks@the logic as a whole...

tfr->len * 9ULL * 100000 / spi_used_hz < 30

A little algebra can change that into:

tfr->len < spi_used_hz / 300000

So rather than add more 64-bit math, it can be removed entirely.  Both
the length and speed are 32 bits and there's no need to multiply them
into something larger than might need 64 bits.

Re: [PATCH] spi: bcm2835aux: use 64-bit arithmetic instead of 32-bit

[Trent Piepho]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="utf-8", Size: 1755 bytes --]

On Wed, 2018-02-07 at 10:00 -0600, Gustavo A. R. Silva wrote:
> Add suffix ULL to constant 9 in order to give the compiler complete
> information about the proper arithmetic to use. Notice that this
> constant is used in a context that expects an expression of type
> unsigned long long (64 bits, unsigned).
> 
> The expression tfr->len * 9 * 1000000 is currently being evaluated
> using 32-bit arithmetic.
> 
> Addresses-Coverity-ID: 1339619
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/spi/spi-bcm2835aux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
> index 7428091..a768c23 100644
> --- a/drivers/spi/spi-bcm2835aux.c
> +++ b/drivers/spi/spi-bcm2835aux.c
> @@ -363,7 +363,7 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
>  	 * chunk getting transferred - in our case the chunk size
>  	 * is 3 bytes, so we approximate this by 9 bits/byte
>  	 */
> -	xfer_time_us = tfr->len * 9 * 1000000;
> +	xfer_time_us = tfr->len * 9ULL * 1000000;
>  	do_div(xfer_time_us, spi_used_hz);
>  
>  	/* run in polling mode for short transfers */
	if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US)

If one looks at the logic as a whole...

tfr->len * 9ULL * 100000 / spi_used_hz < 30

A little algebra can change that into:

tfr->len < spi_used_hz / 300000

So rather than add more 64-bit math, it can be removed entirely.  Both
the length and speed are 32 bits and there's no need to multiply them
into something larger than might need 64 bits.
N‹§²æìr¸›yúèšØb²X¬¶Ç§vØ^–)Þº{.nÇ+‰·¥Š{±²˜¢žØ^n‡r¡ö¦zË\x1aëh™¨è­Ú&¢îý»\x05ËÛÔØï¦v¬Îf\x1dp)¹¹br	šê+€Ê+zf£¢·hšˆ§~†­†Ûiÿûàz¹\x1e®w¥¢¸?™¨è­Ú&¢)ߢ^[f

[PATCH] spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc

[Trent Piepho]

We want to check for xfers that are over 30 microseconds.  Rather than
find how many µs a xfer will take, instead find how many bytes can be
transferred in 30 µs.  The latter must be less than 32 bits (since our
clock speed is limited to 32 bits), while the former involves 64 bit
quantities and more arithmetic operations.

Signed-off-by: Trent Piepho <tpiepho@impinj.com>
---
 drivers/spi/spi-bcm2835aux.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index 7428091d3f5b..1431cb98fe40 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -321,7 +321,6 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
 	unsigned long spi_hz, clk_hz, speed;
 	unsigned long spi_used_hz;
-	unsigned long long xfer_time_us;
 
 	/* calculate the registers to handle
 	 *
@@ -358,20 +357,21 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 	bs->rx_len = tfr->len;
 	bs->pending = 0;
 
-	/* calculate the estimated time in us the transfer runs
-	 * note that there are are 2 idle clocks after each
-	 * chunk getting transferred - in our case the chunk size
-	 * is 3 bytes, so we approximate this by 9 bits/byte
+	/* Calculate the estimated time in us the transfer runs.  Note that
+	 * there are are 2 idle clocks cycles after each chunk getting
+	 * transferred - in our case the chunk size is 3 bytes, so we
+	 * approximate this by 9 cycles/byte.  This is used to find the number
+	 * of Hz per byte per polling limit.  E.g., we can transfer 1 byte in
+	 * 30 µs per 300,000 Hz of bus clock.
 	 */
-	xfer_time_us = tfr->len * 9 * 1000000;
-	do_div(xfer_time_us, spi_used_hz);
-
+#define HZ_PER_BYTE ((9 * 1000000) / BCM2835_AUX_SPI_POLLING_LIMIT_US)
 	/* run in polling mode for short transfers */
-	if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US)
+	if (tfr->len < spi_used_hz / HZ_PER_BYTE)
 		return bcm2835aux_spi_transfer_one_poll(master, spi, tfr);
 
 	/* run in interrupt mode for all others */
 	return bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
+#undef HZ_PER_BYTE
 }
 
 static int bcm2835aux_spi_prepare_message(struct spi_master *master,
-- 
2.14.3

[PATCH] spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc

[Trent Piepho]

We want to check for xfers that are over 30 microseconds.  Rather than
find how many ?s a xfer will take, instead find how many bytes can be
transferred in 30 ?s.  The latter must be less than 32 bits (since our
clock speed is limited to 32 bits), while the former involves 64 bit
quantities and more arithmetic operations.

Signed-off-by: Trent Piepho <tpiepho@impinj.com>
---
 drivers/spi/spi-bcm2835aux.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index 7428091d3f5b..1431cb98fe40 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -321,7 +321,6 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
 	unsigned long spi_hz, clk_hz, speed;
 	unsigned long spi_used_hz;
-	unsigned long long xfer_time_us;
 
 	/* calculate the registers to handle
 	 *
@@ -358,20 +357,21 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 	bs->rx_len = tfr->len;
 	bs->pending = 0;
 
-	/* calculate the estimated time in us the transfer runs
-	 * note that there are are 2 idle clocks after each
-	 * chunk getting transferred - in our case the chunk size
-	 * is 3 bytes, so we approximate this by 9 bits/byte
+	/* Calculate the estimated time in us the transfer runs.  Note that
+	 * there are are 2 idle clocks cycles after each chunk getting
+	 * transferred - in our case the chunk size is 3 bytes, so we
+	 * approximate this by 9 cycles/byte.  This is used to find the number
+	 * of Hz per byte per polling limit.  E.g., we can transfer 1 byte in
+	 * 30 ?s per 300,000 Hz of bus clock.
 	 */
-	xfer_time_us = tfr->len * 9 * 1000000;
-	do_div(xfer_time_us, spi_used_hz);
-
+#define HZ_PER_BYTE ((9 * 1000000) / BCM2835_AUX_SPI_POLLING_LIMIT_US)
 	/* run in polling mode for short transfers */
-	if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US)
+	if (tfr->len < spi_used_hz / HZ_PER_BYTE)
 		return bcm2835aux_spi_transfer_one_poll(master, spi, tfr);
 
 	/* run in interrupt mode for all others */
 	return bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
+#undef HZ_PER_BYTE
 }
 
 static int bcm2835aux_spi_prepare_message(struct spi_master *master,
-- 
2.14.3

Re: [PATCH] spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 505 bytes --]

On Mon, Feb 12, 2018 at 11:38:14AM -0800, Trent Piepho wrote:
> We want to check for xfers that are over 30 microseconds.  Rather than
> find how many µs a xfer will take, instead find how many bytes can be
> transferred in 30 µs.  The latter must be less than 32 bits (since our
> clock speed is limited to 32 bits), while the former involves 64 bit
> quantities and more arithmetic operations.

Please don't bury patches in the middle of existing threads, it makes it
much harder to find them.

[-- Attachment #2: signature.asc --]
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[PATCH] spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc

[Mark Brown]

On Mon, Feb 12, 2018 at 11:38:14AM -0800, Trent Piepho wrote:
> We want to check for xfers that are over 30 microseconds.  Rather than
> find how many ?s a xfer will take, instead find how many bytes can be
> transferred in 30 ?s.  The latter must be less than 32 bits (since our
> clock speed is limited to 32 bits), while the former involves 64 bit
> quantities and more arithmetic operations.

Please don't bury patches in the middle of existing threads, it makes it
much harder to find them.
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Re: [PATCH] spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 505 bytes --]

On Mon, Feb 12, 2018 at 11:38:14AM -0800, Trent Piepho wrote:
> We want to check for xfers that are over 30 microseconds.  Rather than
> find how many µs a xfer will take, instead find how many bytes can be
> transferred in 30 µs.  The latter must be less than 32 bits (since our
> clock speed is limited to 32 bits), while the former involves 64 bit
> quantities and more arithmetic operations.

Please don't bury patches in the middle of existing threads, it makes it
much harder to find them.

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Applied "spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc" to the spi tree

[Mark Brown]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 3598 bytes --]

The patch

   spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc

has been applied to the spi tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From d704afffe65c8fab424963c1ba4ec4364c2d6a82 Mon Sep 17 00:00:00 2001
From: Trent Piepho <tpiepho@impinj.com>
Date: Mon, 12 Feb 2018 11:38:14 -0800
Subject: [PATCH] spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

We want to check for xfers that are over 30 microseconds.  Rather than
find how many µs a xfer will take, instead find how many bytes can be
transferred in 30 µs.  The latter must be less than 32 bits (since our
clock speed is limited to 32 bits), while the former involves 64 bit
quantities and more arithmetic operations.

Signed-off-by: Trent Piepho <tpiepho@impinj.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi-bcm2835aux.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index 7428091d3f5b..1431cb98fe40 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -321,7 +321,6 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
 	unsigned long spi_hz, clk_hz, speed;
 	unsigned long spi_used_hz;
-	unsigned long long xfer_time_us;
 
 	/* calculate the registers to handle
 	 *
@@ -358,20 +357,21 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 	bs->rx_len = tfr->len;
 	bs->pending = 0;
 
-	/* calculate the estimated time in us the transfer runs
-	 * note that there are are 2 idle clocks after each
-	 * chunk getting transferred - in our case the chunk size
-	 * is 3 bytes, so we approximate this by 9 bits/byte
+	/* Calculate the estimated time in us the transfer runs.  Note that
+	 * there are are 2 idle clocks cycles after each chunk getting
+	 * transferred - in our case the chunk size is 3 bytes, so we
+	 * approximate this by 9 cycles/byte.  This is used to find the number
+	 * of Hz per byte per polling limit.  E.g., we can transfer 1 byte in
+	 * 30 µs per 300,000 Hz of bus clock.
 	 */
-	xfer_time_us = tfr->len * 9 * 1000000;
-	do_div(xfer_time_us, spi_used_hz);
-
+#define HZ_PER_BYTE ((9 * 1000000) / BCM2835_AUX_SPI_POLLING_LIMIT_US)
 	/* run in polling mode for short transfers */
-	if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US)
+	if (tfr->len < spi_used_hz / HZ_PER_BYTE)
 		return bcm2835aux_spi_transfer_one_poll(master, spi, tfr);
 
 	/* run in interrupt mode for all others */
 	return bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
+#undef HZ_PER_BYTE
 }
 
 static int bcm2835aux_spi_prepare_message(struct spi_master *master,
-- 
2.16.1

Applied "spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc" to the spi tree

[Mark Brown]

The patch

   spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc

has been applied to the spi tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From d704afffe65c8fab424963c1ba4ec4364c2d6a82 Mon Sep 17 00:00:00 2001
From: Trent Piepho <tpiepho@impinj.com>
Date: Mon, 12 Feb 2018 11:38:14 -0800
Subject: [PATCH] spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

We want to check for xfers that are over 30 microseconds.  Rather than
find how many ??s a xfer will take, instead find how many bytes can be
transferred in 30 ??s.  The latter must be less than 32 bits (since our
clock speed is limited to 32 bits), while the former involves 64 bit
quantities and more arithmetic operations.

Signed-off-by: Trent Piepho <tpiepho@impinj.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi-bcm2835aux.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index 7428091d3f5b..1431cb98fe40 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -321,7 +321,6 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
 	unsigned long spi_hz, clk_hz, speed;
 	unsigned long spi_used_hz;
-	unsigned long long xfer_time_us;
 
 	/* calculate the registers to handle
 	 *
@@ -358,20 +357,21 @@ static int bcm2835aux_spi_transfer_one(struct spi_master *master,
 	bs->rx_len = tfr->len;
 	bs->pending = 0;
 
-	/* calculate the estimated time in us the transfer runs
-	 * note that there are are 2 idle clocks after each
-	 * chunk getting transferred - in our case the chunk size
-	 * is 3 bytes, so we approximate this by 9 bits/byte
+	/* Calculate the estimated time in us the transfer runs.  Note that
+	 * there are are 2 idle clocks cycles after each chunk getting
+	 * transferred - in our case the chunk size is 3 bytes, so we
+	 * approximate this by 9 cycles/byte.  This is used to find the number
+	 * of Hz per byte per polling limit.  E.g., we can transfer 1 byte in
+	 * 30 ??s per 300,000 Hz of bus clock.
 	 */
-	xfer_time_us = tfr->len * 9 * 1000000;
-	do_div(xfer_time_us, spi_used_hz);
-
+#define HZ_PER_BYTE ((9 * 1000000) / BCM2835_AUX_SPI_POLLING_LIMIT_US)
 	/* run in polling mode for short transfers */
-	if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US)
+	if (tfr->len < spi_used_hz / HZ_PER_BYTE)
 		return bcm2835aux_spi_transfer_one_poll(master, spi, tfr);
 
 	/* run in interrupt mode for all others */
 	return bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
+#undef HZ_PER_BYTE
 }
 
 static int bcm2835aux_spi_prepare_message(struct spi_master *master,
-- 
2.16.1