[PATCH] ARM: Samsung: add a workaround for get_clock() for serial driver

[PATCH] ARM: Samsung: add a workaround for get_clock() for serial driver

[Marek Szyprowski]

Serial drivers call get_clock() very early, before platform bus
has been set up, this requires a special check to let them get
a proper clock. Without this patch, a serial console is broken
on Universal C210 board.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 arch/arm/plat-samsung/clock.c |   25 ++++++++++++++++++++++++-
 1 files changed, 24 insertions(+), 1 deletions(-)

diff --git a/arch/arm/plat-samsung/clock.c b/arch/arm/plat-samsung/clock.c
index 90a2051..da847f1 100644
--- a/arch/arm/plat-samsung/clock.c
+++ b/arch/arm/plat-samsung/clock.c
@@ -48,6 +48,9 @@
 #include <plat/clock.h>
 #include <plat/cpu.h>
 
+#include <linux/serial_core.h>
+#include <plat/regs-serial.h> /* for s3c24xx_uart_devs */
+
 /* clock information */
 
 static LIST_HEAD(clocks);
@@ -65,6 +68,26 @@ static int clk_null_enable(struct clk *clk, int enable)
 	return 0;
 }
 
+static int dev_is_s3c_uart(struct device *dev)
+{
+	struct platform_device **pdev = s3c24xx_uart_devs;
+	int i;
+	for (i=0; i<ARRAY_SIZE(s3c24xx_uart_devs); i++, pdev++)
+		if (*pdev && dev == &(*pdev)->dev)
+			return 1;
+	return 0;
+}
+
+/* Serial drivers call get_clock() very early, before platform bus
+   has been set up, this requires a special check to let them get
+   a proper clock */
+
+static int dev_is_platform_device(struct device *dev)
+{
+	return dev->bus == &platform_bus_type ||
+	       (dev->bus == NULL && dev_is_s3c_uart(dev));
+}
+
 /* Clock API calls */
 
 struct clk *clk_get(struct device *dev, const char *id)
@@ -73,7 +96,7 @@ struct clk *clk_get(struct device *dev, const char *id)
 	struct clk *clk = ERR_PTR(-ENOENT);
 	int idno;
 
-	if (dev == NULL || dev->bus != &platform_bus_type)
+	if (dev == NULL || !dev_is_platform_device(dev))
 		idno = -1;
 	else
 		idno = to_platform_device(dev)->id;
-- 
1.7.1.569.g6f426

RE: [PATCH] ARM: Samsung: add a workaround for get_clock() for serial driver

[Kukjin Kim]

Marek Szyprowski wrote:
> 
> Serial drivers call get_clock() very early, before platform bus
> has been set up, this requires a special check to let them get
> a proper clock. Without this patch, a serial console is broken
> on Universal C210 board.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> ---
>  arch/arm/plat-samsung/clock.c |   25 ++++++++++++++++++++++++-
>  1 files changed, 24 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/plat-samsung/clock.c b/arch/arm/plat-samsung/clock.c
> index 90a2051..da847f1 100644
> --- a/arch/arm/plat-samsung/clock.c
> +++ b/arch/arm/plat-samsung/clock.c
> @@ -48,6 +48,9 @@
>  #include <plat/clock.h>
>  #include <plat/cpu.h>
> 
> +#include <linux/serial_core.h>
> +#include <plat/regs-serial.h> /* for s3c24xx_uart_devs */
> +
>  /* clock information */
> 
>  static LIST_HEAD(clocks);
> @@ -65,6 +68,26 @@ static int clk_null_enable(struct clk *clk, int enable)
>  	return 0;
>  }
> 
> +static int dev_is_s3c_uart(struct device *dev)
> +{
> +	struct platform_device **pdev = s3c24xx_uart_devs;
> +	int i;
> +	for (i=0; i<ARRAY_SIZE(s3c24xx_uart_devs); i++, pdev++)
> +		if (*pdev && dev == &(*pdev)->dev)
> +			return 1;
> +	return 0;
> +}
> +
> +/* Serial drivers call get_clock() very early, before platform bus
> +   has been set up, this requires a special check to let them get
> +   a proper clock */
> +
> +static int dev_is_platform_device(struct device *dev)
> +{
> +	return dev->bus == &platform_bus_type ||
> +	       (dev->bus == NULL && dev_is_s3c_uart(dev));
> +}
> +
>  /* Clock API calls */
> 
>  struct clk *clk_get(struct device *dev, const char *id)
> @@ -73,7 +96,7 @@ struct clk *clk_get(struct device *dev, const char *id)
>  	struct clk *clk = ERR_PTR(-ENOENT);
>  	int idno;
> 
> -	if (dev == NULL || dev->bus != &platform_bus_type)
> +	if (dev == NULL || !dev_is_platform_device(dev))
>  		idno = -1;
>  	else
>  		idno = to_platform_device(dev)->id;
> --
Hi,

It works well on SMDKV310 and SMDKC210 with your patch.
But I'm not sure whether this is real solution for this situation.

Anyway I think we need to sort out this stuff in future time.

Ben,
If you're ok, I will apply this.

Thanks.

Best regards,
Kgene.
--
Kukjin Kim <kgene.kim@samsung.com>, Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.