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From: Richard Cochran <richardcochran@gmail.com>
To: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	netdev@vger.kernel.org, Mugunthan V N <mugunthanvnm@ti.com>,
	Sekhar Nori <nsekhar@ti.com>,
	linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org,
	WingMan Kwok <w-kwok2@ti.com>,
	John Stultz <john.stultz@linaro.org>
Subject: Re: [PATCH 7/9] net: ethernet: ti: cpts: calc mult and shift from refclk freq
Date: Wed, 14 Sep 2016 23:03:32 +0200	[thread overview]
Message-ID: <20160914210332.GG12195@netboy> (raw)
In-Reply-To: <4add2983-bdfe-8436-de62-4b2fdc2ea750@ti.com>

On Wed, Sep 14, 2016 at 11:47:46PM +0300, Grygorii Strashko wrote:
> As I understand (and tested), clocks_calc_mult_shift() will 
> return max possible mult which can be used without overflow.

Yes, BUT the returned values depends on the @maxsec input.  As the
kerneldec says,

 * Larger ranges may reduce the conversion accuracy by chosing smaller
 * mult and shift factors.

In addition to that, frequency tuning by calculating a percentage of
'mult', and if 'mult' is small, then the tuning resolution is poor.

So we don't want @maxsec as large as possible, but as small as
possible.

> if calculated results do not satisfy end user - the custom values can
> be passed in DT.  

If we calculate automatically, then the result had better well be
optimal or nearly so.  Otherwise, we should leave it as a manual input
via DTS, IMHO, so that someone is forced to check the values.

Thanks,
Richard

  reply	other threads:[~2016-09-14 21:03 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-14 13:02 [PATCH 0/9] net: ethernet: ti: cpts: update and fixes Grygorii Strashko
2016-09-14 13:02 ` Grygorii Strashko
2016-09-14 13:02 ` [PATCH 1/9] net: ethernet: ti: exclude cpts from build when disabled Grygorii Strashko
2016-09-14 13:02   ` Grygorii Strashko
2016-09-14 13:02 ` [PATCH 2/9] net: ethernet: ti: cpsw: minimize direct access to struct cpts Grygorii Strashko
2016-09-14 13:02   ` Grygorii Strashko
2016-09-14 13:02 ` [PATCH 3/9] net: ethernet: ti: cpts: rework initialization/deinitialization Grygorii Strashko
2016-09-14 13:02   ` Grygorii Strashko
2016-09-14 13:52   ` Richard Cochran
2016-09-14 20:10     ` Grygorii Strashko
2016-09-14 20:10       ` Grygorii Strashko
2016-09-14 20:32       ` Richard Cochran
2016-09-14 20:37         ` Grygorii Strashko
2016-09-14 20:37           ` Grygorii Strashko
2016-09-14 20:52           ` Richard Cochran
2016-09-14 20:59             ` Grygorii Strashko
2016-09-14 20:59               ` Grygorii Strashko
2016-09-15  8:13   ` Richard Cochran
2016-09-14 13:02 ` [PATCH 4/9] net: ethernet: ti: cpts: move dt props parsing to cpts driver Grygorii Strashko
2016-09-14 13:02   ` Grygorii Strashko
2016-09-14 13:55   ` Richard Cochran
2016-09-14 19:45     ` Grygorii Strashko
2016-09-14 19:45       ` Grygorii Strashko
2016-09-14 20:03       ` Richard Cochran
2016-09-14 13:02 ` [PATCH 5/9] net: ethernet: ti: cpts: add return value to tx and rx timestamp funcitons Grygorii Strashko
2016-09-14 13:02   ` Grygorii Strashko
2016-09-14 14:00   ` Richard Cochran
2016-09-14 13:02 ` [PATCH 6/9] net: ethernet: ti: cpts: clean up event list if event pool is empty Grygorii Strashko
2016-09-14 13:02   ` Grygorii Strashko
2016-09-14 14:14   ` Richard Cochran
2016-09-14 19:54     ` Grygorii Strashko
2016-09-14 19:54       ` Grygorii Strashko
2016-09-14 13:02 ` [PATCH 7/9] net: ethernet: ti: cpts: calc mult and shift from refclk freq Grygorii Strashko
2016-09-14 13:02   ` Grygorii Strashko
2016-09-14 14:22   ` Richard Cochran
2016-09-14 19:59     ` Grygorii Strashko
2016-09-14 19:59       ` Grygorii Strashko
2016-09-14 20:26   ` Richard Cochran
2016-09-14 20:47     ` Grygorii Strashko
2016-09-14 20:47       ` Grygorii Strashko
2016-09-14 21:03       ` Richard Cochran [this message]
2016-09-14 21:14         ` Grygorii Strashko
2016-09-14 21:14           ` Grygorii Strashko
2016-09-15 11:58     ` Richard Cochran
2016-09-15 13:49       ` Richard Cochran
2016-09-14 13:02 ` [PATCH 8/9] net: ethernet: ti: cpts: fix overflow check period Grygorii Strashko
2016-09-14 13:02   ` Grygorii Strashko
2016-09-14 14:25   ` Richard Cochran
2016-09-14 20:03     ` Grygorii Strashko
2016-09-14 20:03       ` Grygorii Strashko
2016-09-14 20:08       ` Richard Cochran
2016-09-14 20:23         ` Grygorii Strashko
2016-09-14 20:23           ` Grygorii Strashko
2016-09-14 20:43           ` Richard Cochran
2016-09-14 20:48             ` Grygorii Strashko
2016-09-14 20:48               ` Grygorii Strashko
2016-09-14 13:02 ` [PATCH 9/9] net: ethernet: ti: cpts: switch to readl/writel_relaxed() Grygorii Strashko
2016-09-14 13:02   ` Grygorii Strashko

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