diff mbox

[v3,1/8] clk: imx: add common logic to detect early UART usage

Message ID 1441638573-6701-2-git-send-email-l.stach@pengutronix.de (mailing list archive)
State New, archived
Headers show

Commit Message

Lucas Stach Sept. 7, 2015, 3:09 p.m. UTC 
Both earlycon and earlyprintk depend on the bootloader setup UART
clocks being retained. This patch adds the common logic to detect such
situations and make the information available to the clock drivers, as
well as adding the facilities to disable those clocks at the end of
the kernel init.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/clk/imx/clk.c | 38 ++++++++++++++++++++++++++++++++++++++
 drivers/clk/imx/clk.h |  1 +
 2 files changed, 39 insertions(+)

Comments

Uwe Kleine-König Sept. 7, 2015, 6:52 p.m. UTC | #1 
Hello Lucas,

On Mon, Sep 07, 2015 at 05:09:26PM +0200, Lucas Stach wrote:
> Both earlycon and earlyprintk depend on the bootloader setup UART
> clocks being retained. This patch adds the common logic to detect such
> situations and make the information available to the clock drivers, as
> well as adding the facilities to disable those clocks at the end of
> the kernel init.
> 
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>  drivers/clk/imx/clk.c | 38 ++++++++++++++++++++++++++++++++++++++
>  drivers/clk/imx/clk.h |  1 +
>  2 files changed, 39 insertions(+)
> 
> diff --git a/drivers/clk/imx/clk.c b/drivers/clk/imx/clk.c
> index df12b5307175..45a073dab435 100644
> --- a/drivers/clk/imx/clk.c
> +++ b/drivers/clk/imx/clk.c
> @@ -73,3 +73,41 @@ void imx_cscmr1_fixup(u32 *val)
>  	*val ^= CSCMR1_FIXUP;
>  	return;
>  }
> +
> +static int imx_keep_uart_clocks __initdata;
> +static struct clk ** const *imx_uart_clocks __initdata;
> +
> +static int __init imx_keep_uart_clocks_param(char *str)
> +{
> +	imx_keep_uart_clocks = 1;
> +
> +	return 0;
> +}
> +__setup_param("earlycon", imx_keep_uart_earlycon,
> +	      imx_keep_uart_clocks_param, 0);
> +__setup_param("earlyprintk", imx_keep_uart_earlyprintk,
> +	      imx_keep_uart_clocks_param, 0);
> +
> +void __init imx_register_uart_clocks(struct clk ** const clks[])
> +{
> +	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]);
> +	}
> +}
> +
> +static int __init imx_clk_disable_uart(void)
> +{
> +	if (imx_keep_uart_clocks) {
> +		int i;
> +
> +		for (i = 0; imx_uart_clocks[i]; i++)
> +			clk_disable_unprepare(*imx_uart_clocks[i]);
> +	}
> +
> +	return 0;
> +}
> +late_initcall_sync(imx_clk_disable_uart);

I bet you didn't test if this works when earlyprintk (or earlycon) is
provided on the command line but imx_register_uart_clocks isn't called
(e.g. because this is a Samsung CPU running a multiarch kernel).

Best regards
Uwe
Lucas Stach Sept. 8, 2015, 8:51 a.m. UTC | #2 
Hi Uwe,

Am Montag, den 07.09.2015, 20:52 +0200 schrieb Uwe Kleine-König:
> Hello Lucas,
> 
> On Mon, Sep 07, 2015 at 05:09:26PM +0200, Lucas Stach wrote:
> > Both earlycon and earlyprintk depend on the bootloader setup UART
> > clocks being retained. This patch adds the common logic to detect such
> > situations and make the information available to the clock drivers, as
> > well as adding the facilities to disable those clocks at the end of
> > the kernel init.
> > 
> > Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> > ---
> >  drivers/clk/imx/clk.c | 38 ++++++++++++++++++++++++++++++++++++++
> >  drivers/clk/imx/clk.h |  1 +
> >  2 files changed, 39 insertions(+)
> > 
> > diff --git a/drivers/clk/imx/clk.c b/drivers/clk/imx/clk.c
> > index df12b5307175..45a073dab435 100644
> > --- a/drivers/clk/imx/clk.c
> > +++ b/drivers/clk/imx/clk.c
> > @@ -73,3 +73,41 @@ void imx_cscmr1_fixup(u32 *val)
> >  	*val ^= CSCMR1_FIXUP;
> >  	return;
> >  }
> > +
> > +static int imx_keep_uart_clocks __initdata;
> > +static struct clk ** const *imx_uart_clocks __initdata;
> > +
> > +static int __init imx_keep_uart_clocks_param(char *str)
> > +{
> > +	imx_keep_uart_clocks = 1;
> > +
> > +	return 0;
> > +}
> > +__setup_param("earlycon", imx_keep_uart_earlycon,
> > +	      imx_keep_uart_clocks_param, 0);
> > +__setup_param("earlyprintk", imx_keep_uart_earlyprintk,
> > +	      imx_keep_uart_clocks_param, 0);
> > +
> > +void __init imx_register_uart_clocks(struct clk ** const clks[])
> > +{
> > +	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]);
> > +	}
> > +}
> > +
> > +static int __init imx_clk_disable_uart(void)
> > +{
> > +	if (imx_keep_uart_clocks) {
> > +		int i;
> > +
> > +		for (i = 0; imx_uart_clocks[i]; i++)
> > +			clk_disable_unprepare(*imx_uart_clocks[i]);
> > +	}
> > +
> > +	return 0;
> > +}
> > +late_initcall_sync(imx_clk_disable_uart);
> 
> I bet you didn't test if this works when earlyprintk (or earlycon) is
> provided on the command line but imx_register_uart_clocks isn't called
> (e.g. because this is a Samsung CPU running a multiarch kernel).
> 
Ah, damn! Thanks for spotting.

Regards,
Lucas
diff mbox

Patch

diff --git a/drivers/clk/imx/clk.c b/drivers/clk/imx/clk.c
index df12b5307175..45a073dab435 100644
--- a/drivers/clk/imx/clk.c
+++ b/drivers/clk/imx/clk.c
@@ -73,3 +73,41 @@  void imx_cscmr1_fixup(u32 *val)
 	*val ^= CSCMR1_FIXUP;
 	return;
 }
+
+static int imx_keep_uart_clocks __initdata;
+static struct clk ** const *imx_uart_clocks __initdata;
+
+static int __init imx_keep_uart_clocks_param(char *str)
+{
+	imx_keep_uart_clocks = 1;
+
+	return 0;
+}
+__setup_param("earlycon", imx_keep_uart_earlycon,
+	      imx_keep_uart_clocks_param, 0);
+__setup_param("earlyprintk", imx_keep_uart_earlyprintk,
+	      imx_keep_uart_clocks_param, 0);
+
+void __init imx_register_uart_clocks(struct clk ** const clks[])
+{
+	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]);
+	}
+}
+
+static int __init imx_clk_disable_uart(void)
+{
+	if (imx_keep_uart_clocks) {
+		int i;
+
+		for (i = 0; imx_uart_clocks[i]; i++)
+			clk_disable_unprepare(*imx_uart_clocks[i]);
+	}
+
+	return 0;
+}
+late_initcall_sync(imx_clk_disable_uart);
diff --git a/drivers/clk/imx/clk.h b/drivers/clk/imx/clk.h
index 1049b0c7d818..c94ac5c26226 100644
--- a/drivers/clk/imx/clk.h
+++ b/drivers/clk/imx/clk.h
@@ -7,6 +7,7 @@ 
 extern spinlock_t imx_ccm_lock;
 
 void imx_check_clocks(struct clk *clks[], unsigned int count);
+void imx_register_uart_clocks(struct clk ** const clks[]);
 
 extern void imx_cscmr1_fixup(u32 *val);