From: "Tomoya MORINAGA" <tomoya-linux@dsn.okisemi.com>
To: "'Wolfgang Grandegger'" <wg@grandegger.com>
Cc: <socketcan-core@lists.berlios.de>, <netdev@vger.kernel.org>,
<linux-kernel@vger.kernel.org>
Subject: RE: About bittiming calculation result
Date: Tue, 8 Feb 2011 10:27:11 +0900 [thread overview]
Message-ID: <93C12206407640199DCDD3A89A333F13@hacdom.okisemi.com> (raw)
In-Reply-To: <4D501555.5000905@grandegger.com>
On Tuesday, February 08, 2011 12:53 AM, Wolfgang Grandegger wrote:
> BTW, it's always possible to specify optimized bit-timing
> parameters directly, e.g. the following seem better:
>
> 800000 60 12 4 4 4 3 793650 0.8% 80.0% 81.0% 1.2%
>
> You could set these with:
>
> $ ip link set can0 type can \
> tq 60 prop-seg 12 phase-seg1 4 phase-seg2 4 sjw 4
I can confirm 800K comms works well using the above.
I wish Can-core could calculate like above.
>> seg1/seg2/sjw/prop_seg must be more than 1 ?
BTW, according to EG20T PCH data sheet,
CAN bit-timing parameters(BRP, Prop_Seg, Phase_Seg1, Phase_Seg2, SJW) must not be set 0.
Thanks,
-----------------------------------------
Tomoya MORINAGA
OKI SEMICONDUCTOR CO., LTD.
> -----Original Message-----
> From: Wolfgang Grandegger [mailto:wg@grandegger.com]
> Sent: Tuesday, February 08, 2011 12:53 AM
> To: Tomoya MORINAGA
> Cc: socketcan-core@lists.berlios.de; netdev@vger.kernel.org;
> linux-kernel@vger.kernel.org
> Subject: Re: About bittiming calculation result
>
> On 02/07/2011 01:00 PM, Wolfgang Grandegger wrote:
> > Hi Tomoya,
> >
> > On 02/07/2011 12:38 PM, Tomoya MORINAGA wrote:
> >> Hi,
> >>
> >> I have a question for bittiming-value calculated by Can-core.
> >>
> >> In case setting like below,
> >> - ip link set can0 type can bitrate 800000
> >> - clock=50MHz
> >> - Use pch_can
> >>
> >> Can-core calculates like below
> >> brp=21
> >> seg1=1
> >> seg2=1
> >> sjw=1
> >> prop_seg=0
> >>
> >> Is "prop_seg=0" true ?
> >
> > Well, only prop_seg+phase_seg=tseg1 is relevant and the
> pch_can driver
> > sets the allowed minimum "tseg1_min1" currently to 1:
> >
> > static struct can_bittiming_const pch_can_bittiming_const = {
> > .name = KBUILD_MODNAME,
> > .tseg1_min = 1,
> > .tseg1_max = 16,
> > .tseg2_min = 1,
> > .tseg2_max = 8,
> > .sjw_max = 4,
> > .brp_min = 1,
> > .brp_max = 1024, /* 6bit + extended 4bit */
> > .brp_inc = 1,
> > };
> >
> >> seg1/seg2/sjw/prop_seg must be more than 1 ?
> >
> > Then "tseg1_min" should be set to *2*.
> >
> >> Also I can see the following kernel error log.
> >> bitrate error 0.7%
> >
> > A clock frequency of 50 MHz is sub-optimal for CAN and some
> bit-rates
> > cannot be reproduced properly. Here is the output of the can-utils
> > program "can-calc-bit-timing" (with an entry for the pch-can added):
> >
> > $ ./can-calc-bit-timing pch-can
> > Bit timing parameters for pch-can with 50.000000 MHz ref clock
> > nominal real Bitrt nom real SampP
> > Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP Bitrate Error SampP
> SampP Error CNF1 CNF2 CNF3
> > 1000000 100 3 3 3 1 5 1000000 0.0% 75.0%
> 70.0% 6.7% 0x05 0x92 0x02
> > 800000 420 0 1 1 1 21 793650 0.8% 80.0%
> 66.6% 16.8% 0x15 0xff 0x00
> > 500000 100 8 8 3 1 5 500000 0.0% 87.5%
> 85.0% 2.9% 0x05 0xbf 0x02
> > 250000 500 3 3 1 1 25 250000 0.0% 87.5%
> 87.5% 0.0% 0x19 0x92 0x00
> > 125000 500 6 7 2 1 25 125000 0.0% 87.5%
> 87.5% 0.0% 0x19 0xb5 0x01
> > 100000 500 8 8 3 1 25 100000 0.0% 87.5%
> 85.0% 2.9% 0x19 0xbf 0x02
> > 50000 2500 3 3 1 1 125 50000 0.0% 87.5%
> 87.5% 0.0% 0x7d 0x92 0x00
> > 20000 2500 8 8 3 1 125 20000 0.0% 87.5%
> 85.0% 2.9% 0x7d 0xbf 0x02
> > 10000 12500 3 3 1 1 625 10000 0.0% 87.5%
> 87.5% 0.0% 0x71 0x92 0x00
> >
> > As you can see, especially 800000 gives rather bad results.
>
> BTW, it's always possible to specify optimized bit-timing
> parameters directly, e.g. the following seem better:
>
> 800000 60 12 4 4 4 3 793650 0.8% 80.0% 81.0% 1.2%
>
> You could set these with:
>
> $ ip link set can0 type can \
> tq 60 prop-seg 12 phase-seg1 4 phase-seg2 4 sjw 4
>
> Wolfgang.
>
next prev parent reply other threads:[~2011-02-08 1:27 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1296818921.git.segoon@openwall.com>
2011-02-04 12:23 ` [PATCH 01/20] mach-omap2: mux: world-writable debugfs files Vasiliy Kulikov
2011-02-04 20:09 ` Tony Lindgren
2011-02-04 12:23 ` [PATCH 02/20] mach-omap2: pm: world-writable debugfs timer files Vasiliy Kulikov
2011-02-04 20:10 ` Tony Lindgren
2011-02-04 22:53 ` Kevin Hilman
2011-02-04 12:23 ` [PATCH 03/20] mach-omap2: smartreflex: world-writable debugfs voltage files Vasiliy Kulikov
2011-02-04 20:10 ` Tony Lindgren
2011-02-04 22:54 ` Kevin Hilman
2011-02-07 5:33 ` Menon, Nishanth
2011-02-04 12:23 ` [PATCH 04/20] mach-ux500: mbox-db5500: world-writable sysfs fifo file Vasiliy Kulikov
2011-02-04 12:23 ` [PATCH 05/20] leds: lp5521: world-writable sysfs engine* files Vasiliy Kulikov
2011-02-04 12:23 ` [PATCH 06/20] leds: lp5523: world-writable engine* sysfs files Vasiliy Kulikov
2011-02-04 12:23 ` [PATCH 07/20] video: sn9c102: world-wirtable " Vasiliy Kulikov
2011-02-04 15:29 ` Mauro Carvalho Chehab
2011-02-04 20:28 ` Luca Risolia
2011-02-04 12:23 ` [PATCH 08/20] mfd: ab3100: world-writable debugfs *_priv files Vasiliy Kulikov
2011-02-18 17:01 ` Vasiliy Kulikov
2011-02-04 12:23 ` [PATCH 09/20] mfd: ab3500: world-writable debugfs register-* files Vasiliy Kulikov
2011-02-04 12:23 ` [PATCH 10/20] mfd: ab8500: " Vasiliy Kulikov
2011-02-04 12:23 ` [PATCH 11/20] misc: ep93xx_pwm: world-writable sysfs files Vasiliy Kulikov
2011-02-04 12:23 ` [PATCH 12/20] net: can: at91_can: " Vasiliy Kulikov
2011-02-04 12:42 ` Kurt Van Dijck
2011-02-04 21:06 ` David Miller
2011-02-07 11:38 ` About bittiming calculation result Tomoya MORINAGA
2011-02-07 12:00 ` Wolfgang Grandegger
2011-02-07 15:52 ` Wolfgang Grandegger
2011-02-08 1:27 ` Tomoya MORINAGA [this message]
2011-02-08 7:57 ` Wolfgang Grandegger
2011-02-08 1:09 ` Tomoya MORINAGA
2011-02-08 3:29 ` Bhupesh SHARMA
2011-02-08 4:11 ` Tomoya MORINAGA
2011-02-04 12:23 ` [PATCH 13/20] net: can: janz-ican3: world-writable sysfs termination file Vasiliy Kulikov
2011-02-04 21:06 ` David Miller
2011-02-04 12:23 ` [PATCH 14/20] platform: x86: acer-wmi: world-writable sysfs threeg file Vasiliy Kulikov
2011-02-04 12:23 ` [PATCH 15/20] platform: x86: asus_acpi: world-writable procfs files Vasiliy Kulikov
2011-02-04 12:53 ` Corentin Chary
2011-02-04 12:24 ` [PATCH 16/20] platform: x86: tc1100-wmi: world-writable sysfs wireless and jogdial files Vasiliy Kulikov
2011-02-04 12:24 ` [PATCH 17/20] rtc: rtc-ds1511: world-writable sysfs nvram file Vasiliy Kulikov
2011-02-04 12:24 ` [PATCH 18/20] scsi: aic94xx: world-writable sysfs update_bios file Vasiliy Kulikov
2011-02-04 12:24 ` [PATCH 19/20] scsi: iscsi: world-writable sysfs priv_sess file Vasiliy Kulikov
2011-03-13 8:28 ` Mike Christie
2011-02-04 12:24 ` [PATCH 20/20] fs: ubifs: world-writable debugfs dump_* files Vasiliy Kulikov
2011-02-06 15:16 ` Artem Bityutskiy
2011-02-21 11:42 ` [PATCH 00/20] world-writable files in sysfs and debugfs Samuel Ortiz
2011-03-12 20:23 ` Vasiliy Kulikov
2011-03-14 22:18 ` [Security] " Andrew Morton
2011-03-15 2:26 ` James Bottomley
2011-03-15 3:09 ` [Security] " Greg KH
2011-03-15 11:50 ` James Bottomley
2011-03-15 14:18 ` Greg KH
2011-03-15 14:25 ` James Bottomley
2011-03-15 16:08 ` Vasiliy Kulikov
2011-03-15 16:32 ` James Bottomley
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