From: Tomi Valkeinen <tomi.valkeinen@ti.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
Liu Ying <Ying.Liu@freescale.com>,
<dri-devel@lists.freedesktop.org>, <stefan.wahren@i2se.com>,
<devicetree@vger.kernel.org>, <kernel@pengutronix.de>,
<sboyd@codeaurora.org>, <linux-kernel@vger.kernel.org>,
<a.hajda@samsung.com>, <andy.yan@rock-chips.com>,
<mturquette@linaro.org>, <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH RFC v9 01/20] clk: divider: Correct parent clk round rate if no bestdiv is normally found
Date: Mon, 16 Feb 2015 13:18:13 +0200 [thread overview]
Message-ID: <54E1D1F5.2050603@ti.com> (raw)
In-Reply-To: <20150213185713.GA12209@pengutronix.de>
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On 13/02/15 20:57, Sascha Hauer wrote:
> On Fri, Feb 13, 2015 at 04:35:36PM +0200, Tomi Valkeinen wrote:
>> On 12/02/15 15:41, Sascha Hauer wrote:
>>
>>> Tomis patch is based on the assumption that clk_set_rate(clk_round_rate(rate))
>>> is equal to clk_round_rate(rate). So when this assumption is wrong then
>>> it should simply be reverted.
>>
>> When is it not equal?
>>
>> I agree that doing clk_set_rate(clk, clk_round_rate(clk, rate)) is
>> pointless, but shouldn't it still work?
>>
>> And we can forget about clk_round_rate. Without my patch, this would
>> behave oddly also:
>>
>> rate = clk_get_rate(clk);
>> clk_set_rate(clk, rate);
>>
>> The end result could be something else than 'rate'.
>
> I agree that it's a bit odd, but I think it has to be like this.
> Consider that you request a rate of 100Hz, but the clock can only
> produce 99.5Hz, so due to rounding clk_round_rate() returns 99Hz.
> Now when you request 99Hz from clk_set_rate() the 99.5Hz value
> can't be used because it's too high.
Would that problem better be fixed by changing the clock driver so that
when asked for 99Hz, it would look for rates less than 100Hz?
I think the old behavior was so odd that I would call it broken, so I
hope the current problems can be fixed via some other ways than breaking
it again.
Tomi
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next prev parent reply other threads:[~2015-02-16 11:19 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-12 6:01 [PATCH RFC v9 00/20] Add support for i.MX MIPI DSI DRM driver Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 01/20] clk: divider: Correct parent clk round rate if no bestdiv is normally found Liu Ying
2015-02-12 9:33 ` Sascha Hauer
2015-02-12 10:39 ` Liu Ying
2015-02-12 12:24 ` Sascha Hauer
2015-02-12 12:56 ` Russell King - ARM Linux
2015-02-12 13:41 ` Sascha Hauer
2015-02-12 14:06 ` Liu Ying
2015-02-13 2:58 ` Liu Ying
2015-02-13 2:58 ` Travis
2015-02-13 14:35 ` Tomi Valkeinen
2015-02-13 18:57 ` Sascha Hauer
2015-02-16 11:18 ` Tomi Valkeinen [this message]
2015-02-17 10:32 ` Sascha Hauer
2015-02-16 11:27 ` Russell King - ARM Linux
2015-02-20 19:13 ` Mike Turquette
2015-02-20 19:20 ` Russell King - ARM Linux
2015-02-21 8:56 ` Uwe Kleine-König
2015-02-21 10:40 ` [PATCH 0/3] clk: divider: three exactness fixes (and a rant) Uwe Kleine-König
2015-02-21 10:40 ` [PATCH 1/3] clk: divider: fix calculation of maximal parent rate for a given divider Uwe Kleine-König
2015-02-23 7:32 ` Sascha Hauer
2015-03-05 8:35 ` Uwe Kleine-König
2015-02-21 10:40 ` [PATCH 2/3] clk: divider: fix selection of divider when rounding to closest Uwe Kleine-König
2015-02-23 9:46 ` Maxime Coquelin
2015-02-21 10:40 ` [PATCH 3/3] clk: divider: fix calculation of initial best " Uwe Kleine-König
2015-02-23 9:42 ` Maxime Coquelin
2015-02-23 7:23 ` [PATCH 0/3] clk: divider: three exactness fixes (and a rant) Sascha Hauer
2015-03-06 18:57 ` Mike Turquette
2015-03-06 19:28 ` Uwe Kleine-König
2015-03-06 19:40 ` Stephen Boyd
2015-03-09 9:58 ` Philipp Zabel
2015-03-09 19:05 ` Stephen Boyd
2015-03-09 20:23 ` Uwe Kleine-König
2015-03-09 21:07 ` Mike Turquette
2015-03-09 21:58 ` Uwe Kleine-König
2015-03-09 22:40 ` Stephen Boyd
2015-03-09 23:34 ` Uwe Kleine-König
2015-03-12 1:21 ` Stephen Boyd
2015-03-12 8:57 ` Philipp Zabel
2015-03-13 7:50 ` Uwe Kleine-König
2015-03-13 8:13 ` Philipp Zabel
2015-03-06 19:44 ` Stephen Boyd
2015-03-06 21:09 ` Uwe Kleine-König
2015-02-12 6:01 ` [PATCH RFC v9 02/20] ARM: imx6q: Add GPR3 MIPI muxing control register field shift bits definition Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 03/20] ARM: imx6q: clk: Add the video_27m clock Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 04/20] ARM: imx6q: clk: Change hdmi_isfr clock's parent to be " Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 05/20] ARM: imx6q: clk: Change hsi_tx clock to be a shared clock gate Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 06/20] ARM: imx6q: clk: Add support for mipi_core_cfg clock as " Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 07/20] ARM: imx6q: clk: Add support for mipi_ipg " Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 08/20] ARM: dts: imx6qdl: Move existing MIPI DSI ports into a new 'ports' node Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 09/20] drm/dsi: Add a helper to get bits per pixel of MIPI DSI pixel format Liu Ying
2015-02-12 9:26 ` Daniel Vetter
2015-02-13 5:01 ` Liu Ying
2015-03-03 11:07 ` Philipp Zabel
2015-04-03 3:28 ` Liu Ying
2015-04-09 7:10 ` Thierry Reding
2015-02-12 6:01 ` [PATCH RFC v9 10/20] Documentation: dt-bindings: Add bindings for Synopsys DW MIPI DSI DRM bridge driver Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 11/20] drm/bridge: Add Synopsys DesignWare MIPI DSI host controller driver Liu Ying
2015-04-09 8:43 ` Thierry Reding
2015-04-16 5:39 ` Archit Taneja
2015-04-22 12:13 ` Heiko Stübner
2015-02-12 6:01 ` [PATCH RFC v9 12/20] Documentation: dt-bindings: Add bindings for i.MX specific Synopsys DW MIPI DSI driver Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 13/20] drm: imx: Support Synopsys DesignWare MIPI DSI host controller Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 14/20] Documentation: dt-bindings: Add bindings for Himax HX8369A DRM panel driver Liu Ying
2015-04-09 7:20 ` Thierry Reding
2015-02-12 6:01 ` [PATCH RFC v9 15/20] drm: panel: Add support for Himax HX8369A MIPI DSI panel Liu Ying
2015-04-09 8:09 ` Thierry Reding
2015-02-12 6:01 ` [PATCH RFC v9 16/20] ARM: dtsi: imx6qdl: Add support for MIPI DSI host controller Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 17/20] ARM: dts: imx6qdl-sabresd: Add support for TRULY TFT480800-16-E MIPI DSI panel Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 18/20] ARM: imx_v6_v7_defconfig: Cleanup for imx drm being moved out of staging Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 19/20] ARM: imx_v6_v7_defconfig: Add support for MIPI DSI host controller Liu Ying
2015-02-12 6:01 ` [PATCH RFC v9 20/20] ARM: imx_v6_v7_defconfig: Add support for Himax HX8369A panel Liu Ying
2015-03-02 13:24 ` [PATCH RFC v9 00/20] Add support for i.MX MIPI DSI DRM driver Shawn Guo
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