From: Roger Quadros <rogerq@ti•com>
To: Nishanth Menon <nm@ti•com>, <wg@grandegger•com>, <mkl@pengutronix•de>
Cc: <tony@atomide•com>, <tglx@linutronix•de>, <mugunthanvnm@ti•com>,
<george.cherian@ti•com>, <balbi@ti•com>, <nsekhar@ti•com>,
<sergei.shtylyov@cogentembedded•com>,
<linux-omap@vger•kernel.org>, <linux-can@vger•kernel.org>,
<netdev@vger•kernel.org>
Subject: Re: [PATCH v2 1/3] can: c_can_platform: Fix c_can_hw_raminit_ti() and add timeout
Date: Tue, 9 Sep 2014 17:54:26 +0300 [thread overview]
Message-ID: <540F14A2.6000904@ti.com> (raw)
In-Reply-To: <540F13E4.7020907@ti.com>
On 09/09/2014 05:51 PM, Nishanth Menon wrote:
> On 09/09/2014 09:45 AM, Roger Quadros wrote:
> [...]
>>>> /* We look only at the bits of our instance. */
>>>> val &= mask;
>>>> - while ((readl(priv->raminit_ctrlreg) & mask) != val)
>>>> + while ((readl(priv->raminit_ctrlreg) & mask) != val) {
>>>> udelay(1);
>>>> + timeout++;
>>>> +
>>>> + if (timeout == 1000) {
>>>
>>> How did we come up with this number?
>>
>> wild guess ;), that it should be set in a few microseconds and the delay is not too
>> large.
>>
>> Till I don't hear from hardware guys, it will remain a guess.
>>
>
> in cases like these, I suggest using emperical data as point ->
> example doing some 10,000 iterations of the operation and picking up
> the worse case number and double it.
In my tests the bit was either set immediately or never at all.
Not sure if we should increase it further.
>
> Either way, you need to document the same, else a few years down the
> line, when that number is in question, no one will know what it's
> basis was..
>
OK. I'll add a comment there.
cheers,
-roger
next prev parent reply other threads:[~2014-09-09 14:54 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-09 14:31 [PATCH v2 0/3] net: can: Use syscon regmap for TI specific RAMINIT register Roger Quadros
2014-09-09 14:31 ` [PATCH v2 1/3] can: c_can_platform: Fix c_can_hw_raminit_ti() and add timeout Roger Quadros
2014-09-09 14:34 ` Marc Kleine-Budde
2014-09-09 14:39 ` Roger Quadros
2014-09-16 14:13 ` Marc Kleine-Budde
2014-09-09 14:34 ` Nishanth Menon
2014-09-09 14:45 ` Roger Quadros
2014-09-09 14:51 ` Nishanth Menon
2014-09-09 14:54 ` Roger Quadros [this message]
2014-09-09 14:31 ` [PATCH v2 2/3] net: can: c_can: Add syscon/regmap RAMINIT mechanism Roger Quadros
2014-09-30 13:26 ` Wolfram Sang
2014-09-30 13:33 ` Roger Quadros
2014-09-30 13:52 ` Wolfram Sang
2014-09-30 13:58 ` Roger Quadros
2014-09-30 14:19 ` Wolfram Sang
2014-09-30 14:22 ` Marc Kleine-Budde
2014-09-30 14:49 ` Wolfram Sang
2014-09-30 15:01 ` Marc Kleine-Budde
2014-09-30 15:25 ` Wolfram Sang
2014-09-30 16:04 ` Marc Kleine-Budde
2014-10-01 8:45 ` Roger Quadros
2014-10-01 8:47 ` Marc Kleine-Budde
2014-10-01 9:06 ` Roger Quadros
2014-10-01 10:01 ` Marc Kleine-Budde
2014-10-01 10:12 ` Roger Quadros
2014-10-01 10:26 ` Marc Kleine-Budde
2014-10-01 10:43 ` Wolfram Sang
2014-10-01 10:57 ` Roger Quadros
2014-10-01 11:06 ` Marc Kleine-Budde
2014-10-01 11:10 ` Wolfram Sang
2014-10-01 11:11 ` Marc Kleine-Budde
2014-09-30 13:45 ` Marc Kleine-Budde
2014-09-30 14:02 ` Roger Quadros
2014-09-30 14:11 ` Marc Kleine-Budde
2014-09-09 14:31 ` [PATCH v2 3/3] net: can: c_can: Add support for START pulse in RAMINIT sequence Roger Quadros
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