[PATCH v3 0/8] i.MX early debug UART clock fixes

[PATCH v3 0/8] i.MX early debug UART clock fixes

[Lucas Stach]

This series fixes a long standing interaction issue between the
kernels early debug facilities and the i.MX clock drivers.

Both earlyprintk and earlycon rely on the bootloader setup clocks
for the UARTs to be retained during kernel init. As those clocks are
only enabled in hardware, but not referenced in software they (or even
their parent clocks) may get disabled as a result of other clocks being
en-/disabled during boot.

This results in missing messages from the early debug console until the
regular system console takes over, or even worse system hangs in response
to unclocked register accesses. This renders those debugging facilities a
lot less useful.

The fix implemented here is to check if any of this early debugging is
enabled and keep the UART clocks referenced and enabled in that case.
The clocks will then only be disabled at the end of kernel init, at which
point the real console should have taken over and the early outputs being
disabled.

I've runtime tested this on i.MX6Q and i.MX53, other platforms are only
compile tested. This is mostly a mechanical change, but still I would
appreciate some testing.

Changes since v1:
- reworked logic to require significantly less code in the individual
  clock drivers

Changes since v2:
- fix checkpatch warning about initdata annotation placement
- make code a bit more compact in the for(...) loops
  (since 2 people already commented about this I made up my mind)
- change code style in driver as requested by Shawn
- add more const correctness
  (note that this triggers a false positive checkpatch error in the first patch)

Regards,
Lucas

Lucas Stach (8):
  clk: imx: add common logic to detect early UART usage
  clk: imx25: retain early UART clocks during kernel init
  clk: imx27: retain early UART clocks during kernel init
  clk: imx31: retain early UART clocks during kernel init
  clk: imx35: retain early UART clocks during kernel init
  clk: imx5: retain early UART clocks during kernel init
  clk: imx6: retain early UART clocks during kernel init
  clk: imx7d: retain early UART clocks during kernel init

 drivers/clk/imx/clk-imx25.c       | 12 ++++++++++++
 drivers/clk/imx/clk-imx27.c       | 13 +++++++++++++
 drivers/clk/imx/clk-imx31.c       | 12 ++++++++++++
 drivers/clk/imx/clk-imx35.c       | 10 ++++++++++
 drivers/clk/imx/clk-imx51-imx53.c | 16 ++++++++++++++++
 drivers/clk/imx/clk-imx6q.c       |  8 ++++++++
 drivers/clk/imx/clk-imx6sl.c      |  8 ++++++++
 drivers/clk/imx/clk-imx6sx.c      |  8 ++++++++
 drivers/clk/imx/clk-imx7d.c       | 13 +++++++++++++
 drivers/clk/imx/clk.c             | 38 ++++++++++++++++++++++++++++++++++++++
 drivers/clk/imx/clk.h             |  1 +
 11 files changed, 139 insertions(+)

-- 
2.5.0

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

[Lucas Stach]

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);
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);
 
-- 
2.5.0

[PATCH v3 2/8] clk: imx25: retain early UART clocks during kernel init

[Lucas Stach]

Make sure to keep UART clocks enabled during kernel init if
earlyprintk or earlycon are active.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/clk/imx/clk-imx25.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/clk/imx/clk-imx25.c b/drivers/clk/imx/clk-imx25.c
index ec1a4c1dacf1..c4c141cab444 100644
--- a/drivers/clk/imx/clk-imx25.c
+++ b/drivers/clk/imx/clk-imx25.c
@@ -86,6 +86,16 @@ enum mx25_clks {
 
 static struct clk *clk[clk_max];
 
+static struct clk ** const uart_clks[] __initconst = {
+	&clk[uart_ipg_per],
+	&clk[uart1_ipg],
+	&clk[uart2_ipg],
+	&clk[uart3_ipg],
+	&clk[uart4_ipg],
+	&clk[uart5_ipg],
+	NULL
+};
+
 static int __init __mx25_clocks_init(unsigned long osc_rate,
 				     void __iomem *ccm_base)
 {
@@ -233,6 +243,8 @@ static int __init __mx25_clocks_init(unsigned long osc_rate,
 	 */
 	clk_set_parent(clk[cko_sel], clk[ipg]);
 
+	imx_register_uart_clocks(uart_clks);
+
 	return 0;
 }
 
-- 
2.5.0

[PATCH v3 3/8] clk: imx27: retain early UART clocks during kernel init

[Lucas Stach]

Make sure to keep UART clocks enabled during kernel init if
earlyprintk or earlycon are active.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/clk/imx/clk-imx27.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/clk/imx/clk-imx27.c b/drivers/clk/imx/clk-imx27.c
index d9d50d54ef2a..0d7b8df04dfa 100644
--- a/drivers/clk/imx/clk-imx27.c
+++ b/drivers/clk/imx/clk-imx27.c
@@ -47,6 +47,17 @@ static const char *ssi_sel_clks[] = { "spll_gate", "mpll", };
 static struct clk *clk[IMX27_CLK_MAX];
 static struct clk_onecell_data clk_data;
 
+static struct clk ** const uart_clks[] __initconst = {
+	&clk[IMX27_CLK_PER1_GATE],
+	&clk[IMX27_CLK_UART1_IPG_GATE],
+	&clk[IMX27_CLK_UART2_IPG_GATE],
+	&clk[IMX27_CLK_UART3_IPG_GATE],
+	&clk[IMX27_CLK_UART4_IPG_GATE],
+	&clk[IMX27_CLK_UART5_IPG_GATE],
+	&clk[IMX27_CLK_UART6_IPG_GATE],
+	NULL
+};
+
 static void __init _mx27_clocks_init(unsigned long fref)
 {
 	BUG_ON(!ccm);
@@ -163,6 +174,8 @@ static void __init _mx27_clocks_init(unsigned long fref)
 
 	clk_prepare_enable(clk[IMX27_CLK_EMI_AHB_GATE]);
 
+	imx_register_uart_clocks(uart_clks);
+
 	imx_print_silicon_rev("i.MX27", mx27_revision());
 }
 
-- 
2.5.0

[PATCH v3 4/8] clk: imx31: retain early UART clocks during kernel init

[Lucas Stach]

Make sure to keep UART clocks enabled during kernel init if
earlyprintk or earlycon are active.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/clk/imx/clk-imx31.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/clk/imx/clk-imx31.c b/drivers/clk/imx/clk-imx31.c
index fe66c40b7be2..e283142f123a 100644
--- a/drivers/clk/imx/clk-imx31.c
+++ b/drivers/clk/imx/clk-imx31.c
@@ -62,6 +62,16 @@ enum mx31_clks {
 static struct clk *clk[clk_max];
 static struct clk_onecell_data clk_data;
 
+static struct clk ** const uart_clks[] __initconst = {
+	&clk[ipg],
+	&clk[uart1_gate],
+	&clk[uart2_gate],
+	&clk[uart3_gate],
+	&clk[uart4_gate],
+	&clk[uart5_gate],
+	NULL
+};
+
 int __init mx31_clocks_init(unsigned long fref)
 {
 	void __iomem *base;
@@ -199,6 +209,8 @@ int __init mx31_clocks_init(unsigned long fref)
 	mx31_revision();
 	clk_disable_unprepare(clk[iim_gate]);
 
+	imx_register_uart_clocks(uart_clks);
+
 	mxc_timer_init(MX31_GPT1_BASE_ADDR, MX31_INT_GPT, GPT_TYPE_IMX31);
 
 	return 0;
-- 
2.5.0

[PATCH v3 5/8] clk: imx35: retain early UART clocks during kernel init

[Lucas Stach]

Make sure to keep UART clocks enabled during kernel init if
earlyprintk or earlycon are active.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/clk/imx/clk-imx35.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/clk/imx/clk-imx35.c b/drivers/clk/imx/clk-imx35.c
index 69138ba3dec7..cbe9eee8c80b 100644
--- a/drivers/clk/imx/clk-imx35.c
+++ b/drivers/clk/imx/clk-imx35.c
@@ -84,6 +84,14 @@ enum mx35_clks {
 
 static struct clk *clk[clk_max];
 
+static struct clk ** const uart_clks[] __initconst = {
+	&clk[ipg],
+	&clk[uart1_gate],
+	&clk[uart2_gate],
+	&clk[uart3_gate],
+	NULL
+};
+
 int __init mx35_clocks_init(void)
 {
 	void __iomem *base;
@@ -292,6 +300,8 @@ int __init mx35_clocks_init(void)
 	 */
 	clk_prepare_enable(clk[scc_gate]);
 
+	imx_register_uart_clocks(uart_clks);
+
 	imx_print_silicon_rev("i.MX35", mx35_revision());
 
 	mxc_timer_init(MX35_GPT1_BASE_ADDR, MX35_INT_GPT, GPT_TYPE_IMX31);
-- 
2.5.0

[PATCH v3 6/8] clk: imx5: retain early UART clocks during kernel init

[Lucas Stach]

Make sure to keep UART clocks enabled during kernel init if
earlyprintk or earlycon are active.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/clk/imx/clk-imx51-imx53.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/clk/imx/clk-imx51-imx53.c b/drivers/clk/imx/clk-imx51-imx53.c
index a7e4f394be0d..c6770348d2ab 100644
--- a/drivers/clk/imx/clk-imx51-imx53.c
+++ b/drivers/clk/imx/clk-imx51-imx53.c
@@ -130,6 +130,20 @@ static const char *cpu_podf_sels[] = { "pll1_sw", "step_sel" };
 static struct clk *clk[IMX5_CLK_END];
 static struct clk_onecell_data clk_data;
 
+static struct clk ** const uart_clks[] __initconst = {
+	&clk[IMX5_CLK_UART1_IPG_GATE],
+	&clk[IMX5_CLK_UART1_PER_GATE],
+	&clk[IMX5_CLK_UART2_IPG_GATE],
+	&clk[IMX5_CLK_UART2_PER_GATE],
+	&clk[IMX5_CLK_UART3_IPG_GATE],
+	&clk[IMX5_CLK_UART3_PER_GATE],
+	&clk[IMX5_CLK_UART4_IPG_GATE],
+	&clk[IMX5_CLK_UART4_PER_GATE],
+	&clk[IMX5_CLK_UART5_IPG_GATE],
+	&clk[IMX5_CLK_UART5_PER_GATE],
+	NULL
+};
+
 static void __init mx5_clocks_common_init(void __iomem *ccm_base)
 {
 	clk[IMX5_CLK_DUMMY]		= imx_clk_fixed("dummy", 0);
@@ -310,6 +324,8 @@ static void __init mx5_clocks_common_init(void __iomem *ccm_base)
 	clk_prepare_enable(clk[IMX5_CLK_TMAX1]);
 	clk_prepare_enable(clk[IMX5_CLK_TMAX2]); /* esdhc2, fec */
 	clk_prepare_enable(clk[IMX5_CLK_TMAX3]); /* esdhc1, esdhc4 */
+
+	imx_register_uart_clocks(uart_clks);
 }
 
 static void __init mx50_clocks_init(struct device_node *np)
-- 
2.5.0

[PATCH v3 7/8] clk: imx6: retain early UART clocks during kernel init

[Lucas Stach]

Make sure to keep UART clocks enabled during kernel init if
earlyprintk or earlycon are active.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/clk/imx/clk-imx6q.c  | 8 ++++++++
 drivers/clk/imx/clk-imx6sl.c | 8 ++++++++
 drivers/clk/imx/clk-imx6sx.c | 8 ++++++++
 3 files changed, 24 insertions(+)

diff --git a/drivers/clk/imx/clk-imx6q.c b/drivers/clk/imx/clk-imx6q.c
index d046f8e43de8..4221c038a3ba 100644
--- a/drivers/clk/imx/clk-imx6q.c
+++ b/drivers/clk/imx/clk-imx6q.c
@@ -130,6 +130,12 @@ static inline int clk_on_imx6dl(void)
 	return of_machine_is_compatible("fsl,imx6dl");
 }
 
+static struct clk ** const uart_clks[] __initconst = {
+	&clk[IMX6QDL_CLK_UART_IPG],
+	&clk[IMX6QDL_CLK_UART_SERIAL],
+	NULL
+};
+
 static void __init imx6q_clocks_init(struct device_node *ccm_node)
 {
 	struct device_node *np;
@@ -534,5 +540,7 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
 	/* All existing boards with PCIe use LVDS1 */
 	if (IS_ENABLED(CONFIG_PCI_IMX6))
 		clk_set_parent(clk[IMX6QDL_CLK_LVDS1_SEL], clk[IMX6QDL_CLK_SATA_REF_100M]);
+
+	imx_register_uart_clocks(uart_clks);
 }
 CLK_OF_DECLARE(imx6q, "fsl,imx6q-ccm", imx6q_clocks_init);
diff --git a/drivers/clk/imx/clk-imx6sl.c b/drivers/clk/imx/clk-imx6sl.c
index a0d4cf26cfa9..3c3333faae8e 100644
--- a/drivers/clk/imx/clk-imx6sl.c
+++ b/drivers/clk/imx/clk-imx6sl.c
@@ -184,6 +184,12 @@ void imx6sl_set_wait_clk(bool enter)
 		imx6sl_enable_pll_arm(false);
 }
 
+static struct clk ** const uart_clks[] __initconst = {
+	&clks[IMX6SL_CLK_UART],
+	&clks[IMX6SL_CLK_UART_SERIAL],
+	NULL
+};
+
 static void __init imx6sl_clocks_init(struct device_node *ccm_node)
 {
 	struct device_node *np;
@@ -439,5 +445,7 @@ static void __init imx6sl_clocks_init(struct device_node *ccm_node)
 
 	clk_set_parent(clks[IMX6SL_CLK_LCDIF_AXI_SEL],
 		       clks[IMX6SL_CLK_PLL2_PFD2]);
+
+	imx_register_uart_clocks(uart_clks);
 }
 CLK_OF_DECLARE(imx6sl, "fsl,imx6sl-ccm", imx6sl_clocks_init);
diff --git a/drivers/clk/imx/clk-imx6sx.c b/drivers/clk/imx/clk-imx6sx.c
index 5b95c2c2bf52..f0ad8bbc12f8 100644
--- a/drivers/clk/imx/clk-imx6sx.c
+++ b/drivers/clk/imx/clk-imx6sx.c
@@ -135,6 +135,12 @@ static u32 share_count_ssi1;
 static u32 share_count_ssi2;
 static u32 share_count_ssi3;
 
+static struct clk ** const uart_clks[] __initconst = {
+	&clks[IMX6SX_CLK_UART_IPG],
+	&clks[IMX6SX_CLK_UART_SERIAL],
+	NULL
+};
+
 static void __init imx6sx_clocks_init(struct device_node *ccm_node)
 {
 	struct device_node *np;
@@ -557,5 +563,7 @@ static void __init imx6sx_clocks_init(struct device_node *ccm_node)
 
 	clk_set_parent(clks[IMX6SX_CLK_QSPI1_SEL], clks[IMX6SX_CLK_PLL2_BUS]);
 	clk_set_parent(clks[IMX6SX_CLK_QSPI2_SEL], clks[IMX6SX_CLK_PLL2_BUS]);
+
+	imx_register_uart_clocks(uart_clks);
 }
 CLK_OF_DECLARE(imx6sx, "fsl,imx6sx-ccm", imx6sx_clocks_init);
-- 
2.5.0

[PATCH v3 8/8] clk: imx7d: retain early UART clocks during kernel init

[Lucas Stach]

Make sure to keep UART clocks enabled during kernel init if
earlyprintk or earlycon are active.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/clk/imx/clk-imx7d.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/clk/imx/clk-imx7d.c b/drivers/clk/imx/clk-imx7d.c
index 71f3a94b472c..f86b68049872 100644
--- a/drivers/clk/imx/clk-imx7d.c
+++ b/drivers/clk/imx/clk-imx7d.c
@@ -363,6 +363,17 @@ static const char *pll_video_bypass_sel[] = { "pll_video_main", "pll_video_main_
 
 static struct clk_onecell_data clk_data;
 
+static struct clk ** const uart_clks[] __initconst = {
+	&clks[IMX7D_UART1_ROOT_CLK],
+	&clks[IMX7D_UART2_ROOT_CLK],
+	&clks[IMX7D_UART3_ROOT_CLK],
+	&clks[IMX7D_UART4_ROOT_CLK],
+	&clks[IMX7D_UART5_ROOT_CLK],
+	&clks[IMX7D_UART6_ROOT_CLK],
+	&clks[IMX7D_UART7_ROOT_CLK],
+	NULL
+};
+
 static void __init imx7d_clocks_init(struct device_node *ccm_node)
 {
 	struct device_node *np;
@@ -856,5 +867,7 @@ static void __init imx7d_clocks_init(struct device_node *ccm_node)
 	/* set uart module clock's parent clock source that must be great then 80MHz */
 	clk_set_parent(clks[IMX7D_UART1_ROOT_SRC], clks[IMX7D_OSC_24M_CLK]);
 
+	imx_register_uart_clocks(uart_clks);
+
 }
 CLK_OF_DECLARE(imx7d, "fsl,imx7d-ccm", imx7d_clocks_init);
-- 
2.5.0

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

[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).

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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

[Lucas Stach]

Hi Uwe,

Am Montag, den 07.09.2015, 20:52 +0200 schrieb Uwe Kleine-K?nig:
> 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

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Pengutronix e.K.             | Lucas Stach                 |
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