From: Sascha Hauer <s.hauer@pengutronix.de>
To: Adam Ford <aford173@gmail.com>
Cc: linux-clk <linux-clk@vger.kernel.org>,
Adam Ford-BE <aford@beaconembedded.com>,
charles.steves@logicpd.com, Aisheng Dong <aisheng.dong@nxp.com>,
Michael Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@kernel.org>, Shawn Guo <shawnguo@kernel.org>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
Fabio Estevam <festevam@gmail.com>,
NXP Linux Team <linux-imx@nxp.com>,
Linus Walleij <linus.walleij@linaro.org>,
Jerome Brunet <jbrunet@baylibre.com>,
arm-soc <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] clk: imx: Fix reparenting of UARTs not associated with sdout
Date: Mon, 7 Dec 2020 17:53:44 +0100 [thread overview]
Message-ID: <20201207165344.GP3977@pengutronix.de> (raw)
In-Reply-To: <CAHCN7xJ8kmCxijvzpi+gj=R-QmPc6pqmsMzU5CRt3pQ9B98k+w@mail.gmail.com>
Hi Adam,
On Mon, Dec 07, 2020 at 09:51:33AM -0600, Adam Ford wrote:
> On Sun, Dec 6, 2020 at 11:24 PM Sascha Hauer <s.hauer@pengutronix.de> wrote:
> >
> > Hi Adam,
> >
> > On Fri, Dec 04, 2020 at 12:31:54PM -0600, Adam Ford wrote:
> > > The default clock source on i.MX8M Mini and Nano boards use a 24MHz clock,
> > > but users who need to re-parent the clock source run into issues because
> > > all the UART clocks are enabled whether or not they're needed by sdout.
> > >
> > > Any attempt to change the parent results in an busy error because the
> > > clocks have been enabled already.
> > >
> > > clk: failed to reparent uart1 to sys_pll1_80m: -16
> > >
> > > Instead of pre-initializing all UARTS, scan the device tree to see if UART
> > > clock is used as stdout before initializing it. Only enable the UART clock
> > > if it's needed in order to delay the clock initialization until after the
> > > re-parenting of the clocks.
> > >
> > > Fixes: 9461f7b33d11c ("clk: fix CLK_SET_RATE_GATE with clock rate protection")
> > > Suggested-by: Aisheng Dong <aisheng.dong@nxp.com>
> > > Signed-off-by: Adam Ford <aford173@gmail.com>
> > >
> > > diff --git a/drivers/clk/imx/clk.c b/drivers/clk/imx/clk.c
> > > index 47882c51cb85..6dcc5fbd8f3f 100644
> > > --- a/drivers/clk/imx/clk.c
> > > +++ b/drivers/clk/imx/clk.c
> > > @@ -163,12 +163,18 @@ __setup_param("earlyprintk", imx_keep_uart_earlyprintk,
> > >
> > > void imx_register_uart_clocks(struct clk ** const clks[])
> > > {
> > > + struct clk *uart_clk;
> > > if (imx_keep_uart_clocks) {
> > > int i;
> > >
> > > imx_uart_clocks = clks;
> > > - for (i = 0; imx_uart_clocks[i]; i++)
> > > - clk_prepare_enable(*imx_uart_clocks[i]);
> > > + for (i = 0; imx_uart_clocks[i]; i++) {
> > > + uart_clk = of_clk_get(of_stdout, i);
> >
> > This looks wrong. imx_uart_clocks is an array containing all clocks that
> > could possibly be used for an UART. With of_clk_get(of_stdout, i) you
> > get the nth clock for one specific UART.
> > What you have to do here is: For each of imx_uart_clocks[] you have to
> > iterate over all clocks of the of_stdout node.
>
> Sascha,
>
> Thanks for the review.
>
> I agree that I'm using the wrong index when checking of_stdout, but I
> am not sure we need to loop through imx_uart_clocks at all.
> I looked at the NXP repo, and they just focus on looping through
> of_stdout and don't reference the imx_uart_clocks. Can't we just loop
> through the of_stdout and enable any clocks found in that?
This sounds good. That way we could get rid of the imx_uart_clocks array
entirely.
Note that right below imx_register_uart_clocks() there is imx_clk_disable_uart()
which disables the previously enabled clocks again later when the real
driver has taken over. You'll have to change that as well accordingly.
Sascha
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prev parent reply other threads:[~2020-12-07 16:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-04 18:31 [PATCH] clk: imx: Fix reparenting of UARTs not associated with sdout Adam Ford
2020-12-07 5:24 ` Sascha Hauer
2020-12-07 15:51 ` Adam Ford
2020-12-07 16:53 ` Sascha Hauer [this message]
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