linux-kernel - [PATCH v2] ARM: exynos: add debug_ll_io_init() call in exynos_init

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Message-Id: <1370465793-7997-1-git-send-email-dianders@chromium.org>
Date:	Wed,  5 Jun 2013 13:56:33 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Kukjin Kim <kgene.kim@...sung.com>, Olof Johansson <olof@...om.net>
Cc:	Thomas Abraham <thomas.abraham@...aro.org>,
	Simon Glass <sjg@...omium.org>,
	linux-samsung-soc@...r.kernel.org,
	Tomasz Figa <tomasz.figa@...il.com>,
	Russell King <linux@....linux.org.uk>,
	Ben Dooks <ben-linux@...ff.org>,
	Doug Anderson <dianders@...omium.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] ARM: exynos: add debug_ll_io_init() call in exynos_init_io()

If the early MMU mapping of the UART happens to get booted out of the
TLB between the start of paging_init() and when we finally re-add the
UART at the very end of s3c_init_cpu(), we'll get a hang at bootup if
we've got early_printk enabled.  Avoid this hang by calling
debug_ll_io_init() early.

Without this patch, you can reliably reproduce a hang when early
printk is enabled by adding flush_tlb_all() at the start of
exynos_init_io().  After this patch the hang goes away.

Signed-off-by: Doug Anderson <dianders@...omium.org>
---
Changes in v2:
- Use debug_ll_io_init() instead of reordering printks and adding
  warnings.  Thanks Olof!

 arch/arm/mach-exynos/common.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/mach-exynos/common.c b/arch/arm/mach-exynos/common.c
index 027c9e7..f7e504b 100644
--- a/arch/arm/mach-exynos/common.c
+++ b/arch/arm/mach-exynos/common.c
@@ -386,6 +386,8 @@ int __init exynos_fdt_map_chipid(unsigned long node, const char *uname,
 
 void __init exynos_init_io(struct map_desc *mach_desc, int size)
 {
+	debug_ll_io_init();
+
 #ifdef CONFIG_OF
 	if (initial_boot_params)
 		of_scan_flat_dt(exynos_fdt_map_chipid, NULL);
-- 
1.8.3

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