From: Marco Felsch <m.felsch@pengutronix.de>
To: Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc: Abel Vesa <abelvesa@kernel.org>, Peng Fan <peng.fan@nxp.com>,
Michael Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@kernel.org>, Shawn Guo <shawnguo@kernel.org>,
Sascha Hauer <s.hauer@pengutronix.de>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
Fabio Estevam <festevam@gmail.com>,
NXP Linux Team <linux-imx@nxp.com>,
linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] clk: imx: composite-8m: avoid glitches when set_rate would be a no-op
Date: Tue, 1 Aug 2023 21:45:16 +0200 [thread overview]
Message-ID: <20230801194516.h6gxj2lqmmmls62k@pengutronix.de> (raw)
In-Reply-To: <20230801162731.3278396-1-a.fatoum@pengutronix.de>
On 23-08-01, Ahmad Fatoum wrote:
> Reconfiguring the clock divider to the exact same value is observed
> on an i.MX8MN to often cause a short clock pause, probably because
> the divider restarts counting from the time the register is written.
>
> This issue doesn't show up normally, because the clock framework will
> take care to not call set_rate when the clock rate is the same.
> However, when we configure an upstream clock (e.g. an audio_pll), the
> common code will call set_rate with the newly calculated rate on all
> children. As the new rate is different, we enter set_rate and compute
> the same divider values, write them back and cause the glitch (e.g.
> on a SAI's MCLK).
>
> To avoid the glitch, we skip writing the same value back again.
>
> Fixes: d3ff9728134e ("clk: imx: Add imx composite clock")
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>
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next prev parent reply other threads:[~2023-08-01 19:46 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-01 16:27 [PATCH] clk: imx: composite-8m: avoid glitches when set_rate would be a no-op Ahmad Fatoum
2023-08-01 19:45 ` Marco Felsch [this message]
2023-08-02 1:25 ` Peng Fan
2023-08-02 6:30 ` Ahmad Fatoum
2023-08-04 2:05 ` Peng Fan
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