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[PATCH] iio: adc: vf610_adc: Fix division by zero error

Started bySanchayan Maity <maitysanchayan@gmail.com>
First post2015-10-19 09:50 +0200
Last post2015-10-26 11:50 +0100
Articles 5 — 4 participants

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  [PATCH] iio: adc: vf610_adc: Fix division by zero error Sanchayan Maity <maitysanchayan@gmail.com> - 2015-10-19 09:50 +0200
    Re: [PATCH] iio: adc: vf610_adc: Fix division by zero error Jonathan Cameron <jic23@kernel.org> - 2015-10-25 13:30 +0100
      Re: [PATCH] iio: adc: vf610_adc: Fix division by zero error Stefan Agner <stefan@agner.ch> - 2015-10-26 17:30 +0100
        Re: [PATCH] iio: adc: vf610_adc: Fix division by zero error Jonathan Cameron <jic23@kernel.org> - 2015-10-31 10:40 +0100
    Re: [PATCH] iio: adc: vf610_adc: Fix division by zero error Duan Andy <fugang.duan@freescale.com> - 2015-10-26 11:50 +0100

#1250412 — [PATCH] iio: adc: vf610_adc: Fix division by zero error

FromSanchayan Maity <maitysanchayan@gmail.com>
Date2015-10-19 09:50 +0200
Subject[PATCH] iio: adc: vf610_adc: Fix division by zero error
Message-ID<qldmF-6gR-3@gated-at.bofh.it>
In case the fsl,adck-max-frequency property is not present in
the device tree, a division by zero error results during the
probe call on kernel boot (see below). This patch fixes it and
also restores device tree compatibility in case kernels are
booting with old device trees without this property specified.

[    1.063229] Division by zero in kernel.
[    1.067152] CPU: 0 PID: 1 Comm: swapper Not tainted
4.3.0-rc5-00212-gcc88cef #37
[    1.074650] Hardware name: Freescale Vybrid VF5xx/VF6xx (Device Tree)
[    1.081135] Backtrace:
[    1.083694] [<800134a4>] (dump_backtrace) from [<8001369c>]
(show_stack+0x18/0x1c)
[    1.091340]  r7:00000008 r6:8e0ae210 r5:00000000 r4:8e299800
[    1.097146] [<80013684>] (show_stack) from [<80297b1c>]
(dump_stack+0x24/0x28)
[    1.104483] [<80297af8>] (dump_stack) from [<80013608>]
(__div0+0x1c/0x20)
[    1.111421] [<800135ec>] (__div0) from [<802968b4>] (Ldiv0+0x8/0x10)
[    1.117865] [<80424350>] (vf610_adc_probe) from [<803153b4>]
(platform_drv_probe+0x4c/0xac)
[    1.126311]  r10:00000000 r9:8076a5ec r8:00000000 r7:fffffdfb
r6:807cc67c r5:8e0ae210
[    1.134319]  r4:807f6c54
[    1.136915] [<80315368>] (platform_drv_probe) from [<803138bc>]
(driver_probe_device+0x20c/0x2f8)
[    1.145882]  r7:807cc67c r6:00000000 r5:8e0ae210 r4:807f6c54
[    1.151657] [<803136b0>] (driver_probe_device) from [<80313a3c>]
(__driver_attach+0x94/0x98)
[    1.160190]  r9:8076a5ec r8:00000098 r7:00000000 r6:8e0ae244
r5:807cc67c r4:8e0ae210
[    1.168112] [<803139a8>] (__driver_attach) from [<80311cb8>]
(bus_for_each_dev+0x70/0xa4)
[    1.176383]  r7:00000000 r6:803139a8 r5:807cc67c r4:00000000
[    1.182159] [<80311c48>] (bus_for_each_dev) from [<80313318>]
(driver_attach+0x24/0x28)
[    1.190260]  r6:807bb568 r5:8e2a5b00 r4:807cc67c
[    1.194996] [<803132f4>] (driver_attach) from [<80312f50>]
(bus_add_driver+0x1a4/0x21c)
[    1.203113] [<80312dac>] (bus_add_driver) from [<803142a8>]
(driver_register+0x80/0x100)
[    1.211275]  r7:8e2a7dc0 r6:807a8160 r5:80789e14 r4:807cc67c
[    1.217075] [<80314228>] (driver_register) from [<803152f8>]
(__platform_driver_register+0x5c/0x64)
[    1.226216]  r5:80789e14 r4:807a8160
[    1.229877] [<8031529c>] (__platform_driver_register) from
[<80789e30>] (vf610_adc_driver_init+0x1c/0x20)
[    1.239556] [<80789e14>] (vf610_adc_driver_init) from [<800095f8>]
(do_one_initcall+0x94/0x1dc)
[    1.248365] [<80009564>] (do_one_initcall) from [<8076ae34>]
(kernel_init_freeable+0x13c/0x1e0)
[    1.257155]  r10:80794830 r9:8076a5ec r8:00000098 r7:807d5780
r6:807d5780 r5:00000006
[    1.265153]  r4:807a0ee8
[    1.267753] [<8076acf8>] (kernel_init_freeable) from [<80590ef0>]
(kernel_init+0x18/0xf0)
[    1.276021]  r10:00000000 r9:00000000 r8:00000000 r7:00000000
r6:00000000 r5:80590ed8
[    1.284015]  r4:807d5780
[    1.286615] [<80590ed8>] (kernel_init) from [<8000f878>]
(ret_from_fork+0x14/0x3c)
[    1.294278]  r5:80590ed8 r4:00000000

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
---
 drivers/iio/adc/vf610_adc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
index 6bf4c20..bf4f3d8 100644
--- a/drivers/iio/adc/vf610_adc.c
+++ b/drivers/iio/adc/vf610_adc.c
@@ -193,6 +193,8 @@ static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
 		adc_feature->clk_div = 8;
 	}
 
+	adck_rate = ipg_rate / info->adc_feature.clk_div;
+
 	/*
 	 * Determine the long sample time adder value to be used based
 	 * on the default minimum sample time provided.
@@ -217,7 +219,6 @@ static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
 	 * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit mode
 	 * LSTAdder(Long Sample Time): 3, 5, 7, 9, 13, 17, 21, 25 ADCK cycles
 	 */
-	adck_rate = ipg_rate / info->adc_feature.clk_div;
 	for (i = 0; i < ARRAY_SIZE(vf610_hw_avgs); i++)
 		info->sample_freq_avail[i] =
 			adck_rate / (6 + vf610_hw_avgs[i] *
-- 
2.6.1

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#1255378

FromJonathan Cameron <jic23@kernel.org>
Date2015-10-25 13:30 +0100
Message-ID<qnsAW-2Wk-17@gated-at.bofh.it>
In reply to#1250412
On 19/10/15 08:43, Sanchayan Maity wrote:
> In case the fsl,adck-max-frequency property is not present in
> the device tree, a division by zero error results during the
> probe call on kernel boot (see below). This patch fixes it and
> also restores device tree compatibility in case kernels are
> booting with old device trees without this property specified.
> 
> [    1.063229] Division by zero in kernel.
> [    1.067152] CPU: 0 PID: 1 Comm: swapper Not tainted
> 4.3.0-rc5-00212-gcc88cef #37
> [    1.074650] Hardware name: Freescale Vybrid VF5xx/VF6xx (Device Tree)
> [    1.081135] Backtrace:
> [    1.083694] [<800134a4>] (dump_backtrace) from [<8001369c>]
> (show_stack+0x18/0x1c)
> [    1.091340]  r7:00000008 r6:8e0ae210 r5:00000000 r4:8e299800
> [    1.097146] [<80013684>] (show_stack) from [<80297b1c>]
> (dump_stack+0x24/0x28)
> [    1.104483] [<80297af8>] (dump_stack) from [<80013608>]
> (__div0+0x1c/0x20)
> [    1.111421] [<800135ec>] (__div0) from [<802968b4>] (Ldiv0+0x8/0x10)
> [    1.117865] [<80424350>] (vf610_adc_probe) from [<803153b4>]
> (platform_drv_probe+0x4c/0xac)
> [    1.126311]  r10:00000000 r9:8076a5ec r8:00000000 r7:fffffdfb
> r6:807cc67c r5:8e0ae210
> [    1.134319]  r4:807f6c54
> [    1.136915] [<80315368>] (platform_drv_probe) from [<803138bc>]
> (driver_probe_device+0x20c/0x2f8)
> [    1.145882]  r7:807cc67c r6:00000000 r5:8e0ae210 r4:807f6c54
> [    1.151657] [<803136b0>] (driver_probe_device) from [<80313a3c>]
> (__driver_attach+0x94/0x98)
> [    1.160190]  r9:8076a5ec r8:00000098 r7:00000000 r6:8e0ae244
> r5:807cc67c r4:8e0ae210
> [    1.168112] [<803139a8>] (__driver_attach) from [<80311cb8>]
> (bus_for_each_dev+0x70/0xa4)
> [    1.176383]  r7:00000000 r6:803139a8 r5:807cc67c r4:00000000
> [    1.182159] [<80311c48>] (bus_for_each_dev) from [<80313318>]
> (driver_attach+0x24/0x28)
> [    1.190260]  r6:807bb568 r5:8e2a5b00 r4:807cc67c
> [    1.194996] [<803132f4>] (driver_attach) from [<80312f50>]
> (bus_add_driver+0x1a4/0x21c)
> [    1.203113] [<80312dac>] (bus_add_driver) from [<803142a8>]
> (driver_register+0x80/0x100)
> [    1.211275]  r7:8e2a7dc0 r6:807a8160 r5:80789e14 r4:807cc67c
> [    1.217075] [<80314228>] (driver_register) from [<803152f8>]
> (__platform_driver_register+0x5c/0x64)
> [    1.226216]  r5:80789e14 r4:807a8160
> [    1.229877] [<8031529c>] (__platform_driver_register) from
> [<80789e30>] (vf610_adc_driver_init+0x1c/0x20)
> [    1.239556] [<80789e14>] (vf610_adc_driver_init) from [<800095f8>]
> (do_one_initcall+0x94/0x1dc)
> [    1.248365] [<80009564>] (do_one_initcall) from [<8076ae34>]
> (kernel_init_freeable+0x13c/0x1e0)
> [    1.257155]  r10:80794830 r9:8076a5ec r8:00000098 r7:807d5780
> r6:807d5780 r5:00000006
> [    1.265153]  r4:807a0ee8
> [    1.267753] [<8076acf8>] (kernel_init_freeable) from [<80590ef0>]
> (kernel_init+0x18/0xf0)
> [    1.276021]  r10:00000000 r9:00000000 r8:00000000 r7:00000000
> r6:00000000 r5:80590ed8
> [    1.284015]  r4:807d5780
> [    1.286615] [<80590ed8>] (kernel_init) from [<8000f878>]
> (ret_from_fork+0x14/0x3c)
> [    1.294278]  r5:80590ed8 r4:00000000
> 
> Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
I'd like an ack from Fugang on this as I'm less than entirely
sure what the current logic is doing!

Jonathan
> ---
>  drivers/iio/adc/vf610_adc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
> index 6bf4c20..bf4f3d8 100644
> --- a/drivers/iio/adc/vf610_adc.c
> +++ b/drivers/iio/adc/vf610_adc.c
> @@ -193,6 +193,8 @@ static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
>  		adc_feature->clk_div = 8;
>  	}
>  
> +	adck_rate = ipg_rate / info->adc_feature.clk_div;
> +
>  	/*
>  	 * Determine the long sample time adder value to be used based
>  	 * on the default minimum sample time provided.
> @@ -217,7 +219,6 @@ static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
>  	 * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit mode
>  	 * LSTAdder(Long Sample Time): 3, 5, 7, 9, 13, 17, 21, 25 ADCK cycles
>  	 */
> -	adck_rate = ipg_rate / info->adc_feature.clk_div;
>  	for (i = 0; i < ARRAY_SIZE(vf610_hw_avgs); i++)
>  		info->sample_freq_avail[i] =
>  			adck_rate / (6 + vf610_hw_avgs[i] *
> 

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#1256147

FromStefan Agner <stefan@agner.ch>
Date2015-10-26 17:30 +0100
Message-ID<qnSOL-23f-19@gated-at.bofh.it>
In reply to#1255378
On 2015-10-25 05:20, Jonathan Cameron wrote:
> On 19/10/15 08:43, Sanchayan Maity wrote:
>> In case the fsl,adck-max-frequency property is not present in
>> the device tree, a division by zero error results during the
>> probe call on kernel boot (see below). This patch fixes it and
>> also restores device tree compatibility in case kernels are
>> booting with old device trees without this property specified.
>>
>> [    1.063229] Division by zero in kernel.
>> [    1.067152] CPU: 0 PID: 1 Comm: swapper Not tainted
>> 4.3.0-rc5-00212-gcc88cef #37
>> [    1.074650] Hardware name: Freescale Vybrid VF5xx/VF6xx (Device Tree)
>> [    1.081135] Backtrace:
>> [    1.083694] [<800134a4>] (dump_backtrace) from [<8001369c>]
>> (show_stack+0x18/0x1c)
>> [    1.091340]  r7:00000008 r6:8e0ae210 r5:00000000 r4:8e299800
>> [    1.097146] [<80013684>] (show_stack) from [<80297b1c>]
>> (dump_stack+0x24/0x28)
>> [    1.104483] [<80297af8>] (dump_stack) from [<80013608>]
>> (__div0+0x1c/0x20)
>> [    1.111421] [<800135ec>] (__div0) from [<802968b4>] (Ldiv0+0x8/0x10)
>> [    1.117865] [<80424350>] (vf610_adc_probe) from [<803153b4>]
>> (platform_drv_probe+0x4c/0xac)
>> [    1.126311]  r10:00000000 r9:8076a5ec r8:00000000 r7:fffffdfb
>> r6:807cc67c r5:8e0ae210
>> [    1.134319]  r4:807f6c54
>> [    1.136915] [<80315368>] (platform_drv_probe) from [<803138bc>]
>> (driver_probe_device+0x20c/0x2f8)
>> [    1.145882]  r7:807cc67c r6:00000000 r5:8e0ae210 r4:807f6c54
>> [    1.151657] [<803136b0>] (driver_probe_device) from [<80313a3c>]
>> (__driver_attach+0x94/0x98)
>> [    1.160190]  r9:8076a5ec r8:00000098 r7:00000000 r6:8e0ae244
>> r5:807cc67c r4:8e0ae210
>> [    1.168112] [<803139a8>] (__driver_attach) from [<80311cb8>]
>> (bus_for_each_dev+0x70/0xa4)
>> [    1.176383]  r7:00000000 r6:803139a8 r5:807cc67c r4:00000000
>> [    1.182159] [<80311c48>] (bus_for_each_dev) from [<80313318>]
>> (driver_attach+0x24/0x28)
>> [    1.190260]  r6:807bb568 r5:8e2a5b00 r4:807cc67c
>> [    1.194996] [<803132f4>] (driver_attach) from [<80312f50>]
>> (bus_add_driver+0x1a4/0x21c)
>> [    1.203113] [<80312dac>] (bus_add_driver) from [<803142a8>]
>> (driver_register+0x80/0x100)
>> [    1.211275]  r7:8e2a7dc0 r6:807a8160 r5:80789e14 r4:807cc67c
>> [    1.217075] [<80314228>] (driver_register) from [<803152f8>]
>> (__platform_driver_register+0x5c/0x64)
>> [    1.226216]  r5:80789e14 r4:807a8160
>> [    1.229877] [<8031529c>] (__platform_driver_register) from
>> [<80789e30>] (vf610_adc_driver_init+0x1c/0x20)
>> [    1.239556] [<80789e14>] (vf610_adc_driver_init) from [<800095f8>]
>> (do_one_initcall+0x94/0x1dc)
>> [    1.248365] [<80009564>] (do_one_initcall) from [<8076ae34>]
>> (kernel_init_freeable+0x13c/0x1e0)
>> [    1.257155]  r10:80794830 r9:8076a5ec r8:00000098 r7:807d5780
>> r6:807d5780 r5:00000006
>> [    1.265153]  r4:807a0ee8
>> [    1.267753] [<8076acf8>] (kernel_init_freeable) from [<80590ef0>]
>> (kernel_init+0x18/0xf0)
>> [    1.276021]  r10:00000000 r9:00000000 r8:00000000 r7:00000000
>> r6:00000000 r5:80590ed8
>> [    1.284015]  r4:807d5780
>> [    1.286615] [<80590ed8>] (kernel_init) from [<8000f878>]
>> (ret_from_fork+0x14/0x3c)
>> [    1.294278]  r5:80590ed8 r4:00000000
>>
>> Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
> I'd like an ack from Fugang on this as I'm less than entirely
> sure what the current logic is doing!

I introduced adck_rate along wiht the fsl,adck-max-frequency device tree
property to make sure the ADC operates within its specification. It is
actually also necessary to (re-)calculate the proper adck_rate even when
the fsl,adck-max-frequency property is set. Anyway, moving the
calculation before the first use is the right thing to do. From my side:

Acked-by: Stefan Agner <stefan@agner.ch>

A minor nit below:

> 
> Jonathan
>> ---
>>  drivers/iio/adc/vf610_adc.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
>> index 6bf4c20..bf4f3d8 100644
>> --- a/drivers/iio/adc/vf610_adc.c
>> +++ b/drivers/iio/adc/vf610_adc.c
>> @@ -193,6 +193,8 @@ static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
>>  		adc_feature->clk_div = 8;
>>  	}
>>
>> +	adck_rate = ipg_rate / info->adc_feature.clk_div;
>> +

There is a local pointer variable to adc_feature, so this could look
somewhat shorter:

adck_rate = ipg_rate / adc_feature->clk_div;

--
Stefan

>>  	/*
>>  	 * Determine the long sample time adder value to be used based
>>  	 * on the default minimum sample time provided.
>> @@ -217,7 +219,6 @@ static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
>>  	 * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit mode
>>  	 * LSTAdder(Long Sample Time): 3, 5, 7, 9, 13, 17, 21, 25 ADCK cycles
>>  	 */
>> -	adck_rate = ipg_rate / info->adc_feature.clk_div;
>>  	for (i = 0; i < ARRAY_SIZE(vf610_hw_avgs); i++)
>>  		info->sample_freq_avail[i] =
>>  			adck_rate / (6 + vf610_hw_avgs[i] *
>>
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#1259961

FromJonathan Cameron <jic23@kernel.org>
Date2015-10-31 10:40 +0100
Message-ID<qpANH-16r-1@gated-at.bofh.it>
In reply to#1256147
On 26/10/15 16:21, Stefan Agner wrote:
> On 2015-10-25 05:20, Jonathan Cameron wrote:
>> On 19/10/15 08:43, Sanchayan Maity wrote:
>>> In case the fsl,adck-max-frequency property is not present in
>>> the device tree, a division by zero error results during the
>>> probe call on kernel boot (see below). This patch fixes it and
>>> also restores device tree compatibility in case kernels are
>>> booting with old device trees without this property specified.
>>>
>>> [    1.063229] Division by zero in kernel.
>>> [    1.067152] CPU: 0 PID: 1 Comm: swapper Not tainted
>>> 4.3.0-rc5-00212-gcc88cef #37
>>> [    1.074650] Hardware name: Freescale Vybrid VF5xx/VF6xx (Device Tree)
>>> [    1.081135] Backtrace:
>>> [    1.083694] [<800134a4>] (dump_backtrace) from [<8001369c>]
>>> (show_stack+0x18/0x1c)
>>> [    1.091340]  r7:00000008 r6:8e0ae210 r5:00000000 r4:8e299800
>>> [    1.097146] [<80013684>] (show_stack) from [<80297b1c>]
>>> (dump_stack+0x24/0x28)
>>> [    1.104483] [<80297af8>] (dump_stack) from [<80013608>]
>>> (__div0+0x1c/0x20)
>>> [    1.111421] [<800135ec>] (__div0) from [<802968b4>] (Ldiv0+0x8/0x10)
>>> [    1.117865] [<80424350>] (vf610_adc_probe) from [<803153b4>]
>>> (platform_drv_probe+0x4c/0xac)
>>> [    1.126311]  r10:00000000 r9:8076a5ec r8:00000000 r7:fffffdfb
>>> r6:807cc67c r5:8e0ae210
>>> [    1.134319]  r4:807f6c54
>>> [    1.136915] [<80315368>] (platform_drv_probe) from [<803138bc>]
>>> (driver_probe_device+0x20c/0x2f8)
>>> [    1.145882]  r7:807cc67c r6:00000000 r5:8e0ae210 r4:807f6c54
>>> [    1.151657] [<803136b0>] (driver_probe_device) from [<80313a3c>]
>>> (__driver_attach+0x94/0x98)
>>> [    1.160190]  r9:8076a5ec r8:00000098 r7:00000000 r6:8e0ae244
>>> r5:807cc67c r4:8e0ae210
>>> [    1.168112] [<803139a8>] (__driver_attach) from [<80311cb8>]
>>> (bus_for_each_dev+0x70/0xa4)
>>> [    1.176383]  r7:00000000 r6:803139a8 r5:807cc67c r4:00000000
>>> [    1.182159] [<80311c48>] (bus_for_each_dev) from [<80313318>]
>>> (driver_attach+0x24/0x28)
>>> [    1.190260]  r6:807bb568 r5:8e2a5b00 r4:807cc67c
>>> [    1.194996] [<803132f4>] (driver_attach) from [<80312f50>]
>>> (bus_add_driver+0x1a4/0x21c)
>>> [    1.203113] [<80312dac>] (bus_add_driver) from [<803142a8>]
>>> (driver_register+0x80/0x100)
>>> [    1.211275]  r7:8e2a7dc0 r6:807a8160 r5:80789e14 r4:807cc67c
>>> [    1.217075] [<80314228>] (driver_register) from [<803152f8>]
>>> (__platform_driver_register+0x5c/0x64)
>>> [    1.226216]  r5:80789e14 r4:807a8160
>>> [    1.229877] [<8031529c>] (__platform_driver_register) from
>>> [<80789e30>] (vf610_adc_driver_init+0x1c/0x20)
>>> [    1.239556] [<80789e14>] (vf610_adc_driver_init) from [<800095f8>]
>>> (do_one_initcall+0x94/0x1dc)
>>> [    1.248365] [<80009564>] (do_one_initcall) from [<8076ae34>]
>>> (kernel_init_freeable+0x13c/0x1e0)
>>> [    1.257155]  r10:80794830 r9:8076a5ec r8:00000098 r7:807d5780
>>> r6:807d5780 r5:00000006
>>> [    1.265153]  r4:807a0ee8
>>> [    1.267753] [<8076acf8>] (kernel_init_freeable) from [<80590ef0>]
>>> (kernel_init+0x18/0xf0)
>>> [    1.276021]  r10:00000000 r9:00000000 r8:00000000 r7:00000000
>>> r6:00000000 r5:80590ed8
>>> [    1.284015]  r4:807d5780
>>> [    1.286615] [<80590ed8>] (kernel_init) from [<8000f878>]
>>> (ret_from_fork+0x14/0x3c)
>>> [    1.294278]  r5:80590ed8 r4:00000000
>>>
>>> Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
>> I'd like an ack from Fugang on this as I'm less than entirely
>> sure what the current logic is doing!
> 
> I introduced adck_rate along wiht the fsl,adck-max-frequency device tree
> property to make sure the ADC operates within its specification. It is
> actually also necessary to (re-)calculate the proper adck_rate even when
> the fsl,adck-max-frequency property is set. Anyway, moving the
> calculation before the first use is the right thing to do. From my side:
> 
> Acked-by: Stefan Agner <stefan@agner.ch>
> 
> A minor nit below:
> 
>>
>> Jonathan
>>> ---
>>>  drivers/iio/adc/vf610_adc.c | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
>>> index 6bf4c20..bf4f3d8 100644
>>> --- a/drivers/iio/adc/vf610_adc.c
>>> +++ b/drivers/iio/adc/vf610_adc.c
>>> @@ -193,6 +193,8 @@ static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
>>>  		adc_feature->clk_div = 8;
>>>  	}
>>>
>>> +	adck_rate = ipg_rate / info->adc_feature.clk_div;
>>> +
> 
> There is a local pointer variable to adc_feature, so this could look
> somewhat shorter:
> 
> adck_rate = ipg_rate / adc_feature->clk_div;
Fixed that up and applied to the fixes-togreg branch of iio.git
Marked for stable.

Thanks,

Jonathan
> 
> --
> Stefan
> 
>>>  	/*
>>>  	 * Determine the long sample time adder value to be used based
>>>  	 * on the default minimum sample time provided.
>>> @@ -217,7 +219,6 @@ static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
>>>  	 * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit mode
>>>  	 * LSTAdder(Long Sample Time): 3, 5, 7, 9, 13, 17, 21, 25 ADCK cycles
>>>  	 */
>>> -	adck_rate = ipg_rate / info->adc_feature.clk_div;
>>>  	for (i = 0; i < ARRAY_SIZE(vf610_hw_avgs); i++)
>>>  		info->sample_freq_avail[i] =
>>>  			adck_rate / (6 + vf610_hw_avgs[i] *
>>>

--
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#1255805

FromDuan Andy <fugang.duan@freescale.com>
Date2015-10-26 11:50 +0100
Message-ID<qnNvH-78a-3@gated-at.bofh.it>
In reply to#1250412
From: Sanchayan Maity <maitysanchayan@gmail.com> Sent: Monday, October 19, 2015 3:43 PM
>To: jic23@kernel.org
>Cc: stefan@agner.ch; Duan Fugang-B38611; linux-iio@vger.kernel.org; linux->kernel@vger.kernel.org; Sanchayan Maity
>Subject: [PATCH] iio: adc: vf610_adc: Fix division by zero error
>
>In case the fsl,adck-max-frequency property is not present in
>the device tree, a division by zero error results during the
>probe call on kernel boot (see below). This patch fixes it and
>also restores device tree compatibility in case kernels are
>booting with old device trees without this property specified.
>
>[    1.063229] Division by zero in kernel.
>[    1.067152] CPU: 0 PID: 1 Comm: swapper Not tainted
>4.3.0-rc5-00212-gcc88cef #37
>[    1.074650] Hardware name: Freescale Vybrid VF5xx/VF6xx (Device Tree)
>[    1.081135] Backtrace:
>[    1.083694] [<800134a4>] (dump_backtrace) from [<8001369c>]
>(show_stack+0x18/0x1c)
>[    1.091340]  r7:00000008 r6:8e0ae210 r5:00000000 r4:8e299800
>[    1.097146] [<80013684>] (show_stack) from [<80297b1c>]
>(dump_stack+0x24/0x28)
>[    1.104483] [<80297af8>] (dump_stack) from [<80013608>]
>(__div0+0x1c/0x20)
>[    1.111421] [<800135ec>] (__div0) from [<802968b4>] (Ldiv0+0x8/0x10)
>[    1.117865] [<80424350>] (vf610_adc_probe) from [<803153b4>]
>(platform_drv_probe+0x4c/0xac)
>[    1.126311]  r10:00000000 r9:8076a5ec r8:00000000 r7:fffffdfb
>r6:807cc67c r5:8e0ae210
>[    1.134319]  r4:807f6c54
>[    1.136915] [<80315368>] (platform_drv_probe) from [<803138bc>]
>(driver_probe_device+0x20c/0x2f8)
>[    1.145882]  r7:807cc67c r6:00000000 r5:8e0ae210 r4:807f6c54
>[    1.151657] [<803136b0>] (driver_probe_device) from [<80313a3c>]
>(__driver_attach+0x94/0x98)
>[    1.160190]  r9:8076a5ec r8:00000098 r7:00000000 r6:8e0ae244
>r5:807cc67c r4:8e0ae210
>[    1.168112] [<803139a8>] (__driver_attach) from [<80311cb8>]
>(bus_for_each_dev+0x70/0xa4)
>[    1.176383]  r7:00000000 r6:803139a8 r5:807cc67c r4:00000000
>[    1.182159] [<80311c48>] (bus_for_each_dev) from [<80313318>]
>(driver_attach+0x24/0x28)
>[    1.190260]  r6:807bb568 r5:8e2a5b00 r4:807cc67c
>[    1.194996] [<803132f4>] (driver_attach) from [<80312f50>]
>(bus_add_driver+0x1a4/0x21c)
>[    1.203113] [<80312dac>] (bus_add_driver) from [<803142a8>]
>(driver_register+0x80/0x100)
>[    1.211275]  r7:8e2a7dc0 r6:807a8160 r5:80789e14 r4:807cc67c
>[    1.217075] [<80314228>] (driver_register) from [<803152f8>]
>(__platform_driver_register+0x5c/0x64)
>[    1.226216]  r5:80789e14 r4:807a8160
>[    1.229877] [<8031529c>] (__platform_driver_register) from
>[<80789e30>] (vf610_adc_driver_init+0x1c/0x20)
>[    1.239556] [<80789e14>] (vf610_adc_driver_init) from [<800095f8>]
>(do_one_initcall+0x94/0x1dc)
>[    1.248365] [<80009564>] (do_one_initcall) from [<8076ae34>]
>(kernel_init_freeable+0x13c/0x1e0)
>[    1.257155]  r10:80794830 r9:8076a5ec r8:00000098 r7:807d5780
>r6:807d5780 r5:00000006
>[    1.265153]  r4:807a0ee8
>[    1.267753] [<8076acf8>] (kernel_init_freeable) from [<80590ef0>]
>(kernel_init+0x18/0xf0)
>[    1.276021]  r10:00000000 r9:00000000 r8:00000000 r7:00000000
>r6:00000000 r5:80590ed8
>[    1.284015]  r4:807d5780
>[    1.286615] [<80590ed8>] (kernel_init) from [<8000f878>]
>(ret_from_fork+0x14/0x3c)
>[    1.294278]  r5:80590ed8 r4:00000000
>
>Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>

 Acked-by: Fugang Duan <B38611@freescale.com>--
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