From: Mark Brown <broonie@kernel.org> To: Nicolin Chen <nicoleotsuka@gmail.com> Cc: "Łukasz Majewski" <lukma@denx.de>, "Timur Tabi" <timur@tabi.org>, "Xiubo Li" <Xiubo.Lee@gmail.com>, "Fabio Estevam" <fabio.estevam@nxp.com>, "Liam Girdwood" <lgirdwood@gmail.com>, "Jaroslav Kysela" <perex@perex.cz>, "Takashi Iwai" <tiwai@suse.com>, alsa-devel@alsa-project.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal to system freq Date: Thu, 7 Sep 2017 14:44:11 +0100 [thread overview] Message-ID: <20170907134411.uzwh54lstzmvp6dd@sirena.co.uk> (raw) In-Reply-To: <20170905174528.GA23906@Asurada-Nvidia> [-- Attachment #1: Type: text/plain, Size: 1569 bytes --] On Tue, Sep 05, 2017 at 10:45:29AM -0700, Nicolin Chen wrote: > The ipg clock is merely used to access registers, and has nothing > (directly) to do with external clock outputs. The driver shall not > change the ipg clock as the system ipg clock (its parent clock) > might be messed and even system time would get weird -- happened > once when the fsl_spdif driver used to call clk_set_rate() on its > ipg clock. Although the clock controller should have some kind of > protection in my opinion, we just avoid IP clock rate change in all > audio drivers as well. Yes, the clock API needs constraints code. > On the other hand, the sys clock (baudclk in the driver) should be > configured whenever it's related to external clock outputs. When I > implemented this set_sysclk() for fsl_ssi.c, I used it to set this > sys clock (baudclk) by a machine driver, in order to set bit clock. > Then someone patched the driver by moving all the code to set_bclk() > to make machine drivers simpler. Now the set_sysclk() is remained > to give machine drivers a chance to override clock configurations > in the hw_params(). This could be used in TDM or some other special > cases (It could also have a purpose for backwards compatibility). > So here, we should set baudclk (BCLK generator). No, that's just going to cause confusion - if all the other drivers are using set_sysclk() to set an input clock rate to the IP rather than an output clock but your driver does something else then sooner or later someone will run into trouble with that. [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 488 bytes --]
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From: Mark Brown <broonie@kernel.org> To: Nicolin Chen <nicoleotsuka@gmail.com> Cc: alsa-devel@alsa-project.org, "Timur Tabi" <timur@tabi.org>, "Xiubo Li" <Xiubo.Lee@gmail.com>, linux-kernel@vger.kernel.org, "Takashi Iwai" <tiwai@suse.com>, "Liam Girdwood" <lgirdwood@gmail.com>, "Łukasz Majewski" <lukma@denx.de>, "Fabio Estevam" <fabio.estevam@nxp.com>, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal to system freq Date: Thu, 7 Sep 2017 14:44:11 +0100 [thread overview] Message-ID: <20170907134411.uzwh54lstzmvp6dd@sirena.co.uk> (raw) In-Reply-To: <20170905174528.GA23906@Asurada-Nvidia> [-- Attachment #1.1: Type: text/plain, Size: 1569 bytes --] On Tue, Sep 05, 2017 at 10:45:29AM -0700, Nicolin Chen wrote: > The ipg clock is merely used to access registers, and has nothing > (directly) to do with external clock outputs. The driver shall not > change the ipg clock as the system ipg clock (its parent clock) > might be messed and even system time would get weird -- happened > once when the fsl_spdif driver used to call clk_set_rate() on its > ipg clock. Although the clock controller should have some kind of > protection in my opinion, we just avoid IP clock rate change in all > audio drivers as well. Yes, the clock API needs constraints code. > On the other hand, the sys clock (baudclk in the driver) should be > configured whenever it's related to external clock outputs. When I > implemented this set_sysclk() for fsl_ssi.c, I used it to set this > sys clock (baudclk) by a machine driver, in order to set bit clock. > Then someone patched the driver by moving all the code to set_bclk() > to make machine drivers simpler. Now the set_sysclk() is remained > to give machine drivers a chance to override clock configurations > in the hw_params(). This could be used in TDM or some other special > cases (It could also have a purpose for backwards compatibility). > So here, we should set baudclk (BCLK generator). No, that's just going to cause confusion - if all the other drivers are using set_sysclk() to set an input clock rate to the IP rather than an output clock but your driver does something else then sooner or later someone will run into trouble with that. [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 488 bytes --] [-- Attachment #2: Type: text/plain, Size: 0 bytes --]
next prev parent reply other threads:[~2017-09-07 13:44 UTC|newest] Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-09-03 11:05 [PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal to system freq Lukasz Majewski 2017-09-03 12:44 ` Fabio Estevam 2017-09-03 12:44 ` Fabio Estevam 2017-09-03 14:40 ` Łukasz Majewski 2017-09-03 15:29 ` Fabio Estevam 2017-09-03 15:29 ` Fabio Estevam 2017-09-03 15:29 ` Fabio Estevam 2017-09-05 5:20 ` Nicolin Chen 2017-09-05 8:35 ` Łukasz Majewski 2017-09-05 18:11 ` Nicolin Chen 2017-09-05 21:13 ` Łukasz Majewski 2017-09-05 21:13 ` Łukasz Majewski 2017-09-05 22:52 ` Nicolin Chen 2017-09-05 22:52 ` Nicolin Chen 2017-09-06 9:22 ` Łukasz Majewski 2017-09-06 9:22 ` Łukasz Majewski 2017-09-06 17:33 ` Nicolin Chen 2017-09-06 17:33 ` Nicolin Chen 2017-09-06 18:35 ` Łukasz Majewski 2017-09-06 19:47 ` Nicolin Chen 2017-09-06 19:47 ` Nicolin Chen 2017-09-06 21:18 ` Łukasz Majewski 2017-09-06 21:18 ` Łukasz Majewski 2017-09-07 23:10 ` Łukasz Majewski 2017-09-07 23:10 ` Łukasz Majewski 2017-09-08 0:39 ` Nicolin Chen 2017-09-08 0:39 ` Nicolin Chen 2017-09-05 23:20 ` Fabio Estevam 2017-09-05 23:20 ` Fabio Estevam 2017-09-05 23:20 ` Fabio Estevam 2017-09-06 8:44 ` Łukasz Majewski 2017-09-05 20:14 ` Fabio Estevam 2017-09-05 20:14 ` Fabio Estevam 2017-09-05 21:14 ` Łukasz Majewski 2017-09-05 5:06 ` Nicolin Chen 2017-09-05 7:37 ` Łukasz Majewski 2017-09-05 7:52 ` Nicolin Chen 2017-09-05 8:19 ` Łukasz Majewski 2017-09-05 8:19 ` Łukasz Majewski 2017-09-05 15:15 ` Mark Brown 2017-09-05 15:15 ` Mark Brown 2017-09-05 17:45 ` Nicolin Chen 2017-09-07 13:44 ` Mark Brown [this message] 2017-09-07 13:44 ` Mark Brown 2017-09-07 23:03 ` Nicolin Chen
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