Re: [PATCH] ARM: EXYNOS: Avoid early use of of_machine_is_compatible()

[Olof Johansson <olof@lixom.net>]

On Wed, Nov 28, 2012 at 02:23:09PM +0900, Kukjin Kim wrote:
> Olof Johansson wrote:
> > 
> > On Tue, Nov 27, 2012 at 2:27 PM, Kukjin Kim <kgene.kim@samsung.com> wrote:
> > > On 11/28/12 07:11, Olof Johansson wrote:
> > >>
> > >> On Tue, Nov 27, 2012 at 11:53 AM, Doug Anderson<dianders@chromium.org>
> > >> wrote:
> > >>>
> > >>> The recent commit "ARM: EXYNOS: add support for EXYNOS5440 SoC" broke
> > >>> support for exynos5250 because of_machine_is_compatible() was used too
> > >>> early in the boot process.  It also probably meant that the exynos5440
> > >>> failed to use the proper iotable.  Switch to use
> > >>> of_flat_dt_is_compatible() in both of these cases.
> > >>>
> > >>> The failure I was seeing in exynos5250 because of this was:
> > >>>    Division by zero in kernel.
> > >>>    [<80015ed4>] (unwind_backtrace+0x0/0xec) from [<8045c7a4>]
> > >>> (dump_stack+0x20/0x24)
> > >>>    [<8045c7a4>] (dump_stack+0x20/0x24) from [<80012990>]
> > >>> (__div0+0x20/0x28)
> > >>>    [<80012990>] (__div0+0x20/0x28) from [<8021ab04>]
> (Ldiv0_64+0x8/0x18)
> > >>>    [<8021ab04>] (Ldiv0_64+0x8/0x18) from [<80068560>]
> > >>> (__clocksource_updatefreq_scale+0x54/0x134)
> > >>>    [<80068560>] (__clocksource_updatefreq_scale+0x54/0x134) from
> > >>> [<8006865c>] (__clocksource_register_scale+0x1c/0x54)
> > >>>    [<8006865c>] (__clocksource_register_scale+0x1c/0x54) from
> > >>> [<80612a18>] (exynos_timer_init+0x100/0x1e8)
> > >>>    [<80612a18>] (exynos_timer_init+0x100/0x1e8) from [<8060d184>]
> > >>> (time_init+0x28/0x38)
> > >>>    [<8060d184>] (time_init+0x28/0x38) from [<8060a754>]
> > >>> (start_kernel+0x1e0/0x3c8)
> > >>>    [<8060a754>] (start_kernel+0x1e0/0x3c8) from [<40008078>]
> > (0x40008078)
> > >>>
> > >>> Signed-off-by: Doug Anderson<dianders@chromium.org>
> > >>
> > >>
> > >> Thanks Doug.
> > >>
> > >> Kukjin, I'll apply this directly on top of the previous branch in
> > >> arm-soc, if that's OK with you.
> > >>
> > > Sure, go ahead with my ack if you want,
> > >
> > > Acked-by: Kukjin Kim <kgene.kim@samsung.com>
> > >
> > > Note, actually there was a fix which uses soc_is_exynos5440() in my
> > local
> > > :-) I'm not sure which one is better at this moment, but I'm OK on this.
> > 
> > Ok, applied. Thanks all.
> > 
> Olof, just note, happens build error with exynos4_defconfig because of
> non-DT.

Ick, thanks for catching that.

> 
> Following can resolve it or we should create null function for
> of_get_flat_dt_root() and of_flat_dt_is_compatible()...
> 
> 8<---------------------------------------
> From: Kukjin Kim <kgene.kim@samsung.com>
> Subject: ARM: EXYNOS: fix a build error with non-DT for exynos4
> 
> This fixes following in case of non-DT:
> arch/arm/mach-exynos/common.c: In function 'exynos_init_io':
> arch/arm/mach-exynos/common.c:339: error: implicit declaration of function
> 'of_get_flat_dt_root'
> arch/arm/mach-exynos/common.c:342: error: implicit declaration of function
> 'of_flat_dt_is_compatible'
> make[1]: *** [arch/arm/mach-exynos/common.o] Error 1
> 
> Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
> ---
> diff --git a/arch/arm/mach-exynos/common.c b/arch/arm/mach-exynos/common.c
> index b919f5f..2110091 100644
> --- a/arch/arm/mach-exynos/common.c
> +++ b/arch/arm/mach-exynos/common.c
> @@ -336,12 +336,14 @@ void __init exynos_init_late(void)
> 
>  void __init exynos_init_io(struct map_desc *mach_desc, int size)
>  {
> +#ifdef CONFIG_OF
>  	unsigned long root = of_get_flat_dt_root();
> 
>  	/* initialize the io descriptors we need for initialization */
>  	if (of_flat_dt_is_compatible(root, "samsung,exynos5440"))
>  		iotable_init(exynos5440_iodesc,
> ARRAY_SIZE(exynos5440_iodesc));
>  	else
> +#endif
>  		iotable_init(exynos_iodesc, ARRAY_SIZE(exynos_iodesc));

I really don't like splitting an if/else with an ifdef like this, it's fragile
code and can be hard to follow.

There's also a second build error with exynos_defconfig in the
exynos5-dt.c board file due to a missing include. Teaches me to just apply
patches without trying to build. :(

I'll squash this into Doug's original patch, if that's OK?


diff --git a/arch/arm/mach-exynos/common.c b/arch/arm/mach-exynos/common.c
index 796e0c9..77e7c5b 100644
--- a/arch/arm/mach-exynos/common.c
+++ b/arch/arm/mach-exynos/common.c
@@ -122,6 +122,7 @@ static struct map_desc exynos_iodesc[] __initdata = {
 	},
 };
 
+#ifdef CONFIG_ARCH_EXYNOS5
 static struct map_desc exynos5440_iodesc[] __initdata = {
 	{
 		.virtual	= (unsigned long)S5P_VA_CHIPID,
@@ -130,6 +131,7 @@ static struct map_desc exynos5440_iodesc[] __initdata = {
 		.type		= MT_DEVICE,
 	},
 };
+#endif
 
 static struct map_desc exynos4_iodesc[] __initdata = {
 	{
@@ -347,13 +349,19 @@ void __init exynos_init_late(void)
 
 void __init exynos_init_io(struct map_desc *mach_desc, int size)
 {
+	struct map_desc *iodesc = exynos_iodesc;
+	int iodesc_sz = ARRAY_SIZE(exynos_iodesc);
+#ifdef CONFIG_OF
 	unsigned long root = of_get_flat_dt_root();
 
 	/* initialize the io descriptors we need for initialization */
-	if (of_flat_dt_is_compatible(root, "samsung,exynos5440"))
-		iotable_init(exynos5440_iodesc, ARRAY_SIZE(exynos5440_iodesc));
-	else
-		iotable_init(exynos_iodesc, ARRAY_SIZE(exynos_iodesc));
+	if (of_flat_dt_is_compatible(root, "samsung,exynos5440")) {
+		iodesc = exynos5440_iodesc;
+		iodesc_sz = ARRAY_SIZE(exynos5440_iodesc);
+	}
+#endif
+
+	iotable_init(iodesc, iodesc_sz);
 
 	if (mach_desc)
 		iotable_init(mach_desc, size);
diff --git a/arch/arm/mach-exynos/mach-exynos5-dt.c b/arch/arm/mach-exynos/mach-exynos5-dt.c
index 2a75624..f1326be 100644
--- a/arch/arm/mach-exynos/mach-exynos5-dt.c
+++ b/arch/arm/mach-exynos/mach-exynos5-dt.c
@@ -10,6 +10,7 @@
 */
 
 #include <linux/of_platform.h>
+#include <linux/of_fdt.h>
 #include <linux/serial_core.h>
 
 #include <asm/mach/arch.h>