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Message-ID: <56348AF6.1000806@kernel.org> Date: Sat, 31 Oct 2015 09:33:42 +0000 From: Jonathan Cameron <jic23@...nel.org> To: Stefan Agner <stefan@...er.ch> Cc: Sanchayan Maity <maitysanchayan@...il.com>, b38611@...escale.com, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] iio: adc: vf610_adc: Fix division by zero error 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@...il.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@...er.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] * >>> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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