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@xxxxxxxxx> > 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@xxxxxxxx> 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] * >> -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
