[PATCH] [RFC] ARM OMAP4: enable DSS by default

Christoph Fritz chf.fritz at googlemail.com
Fri Mar 15 09:39:22 EDT 2013

On Fri, 2013-03-15 at 12:40 +0400, Alexander Shiyan wrote:

> MD command causes an error due to the inability of the reading memory area.
> Error can be disabled via the option "enable arm exception handling support",
> but it does not help solve the problem.
> OMAP has a memory areas (modules), which are locked,

This corresponds with my register observations. As noted above, register
CM_DSS_DSS_CLKCTRL (0x4a009120) reads 0x00070F02 which means: "Module is
disabled and cannot be accessed".

>  so you need to
> search this information from datasheet.

Finnaly I was very wise inspired to do "mw 0x4a009100 2". This disables
the HW_AUTO-Mode (Automatic transition) and starts a software forced
wake-up (SW_WKUP).

Now even the IDLEST field from CM_DSS_CLKSTCTRL reads 0x0: "Module is
fully functional, including INTRCONN" :-)

et la voila:
md 0x48040000+4
48040000: 00000040

What do you think about the patch below?

Subject: [PATCH] [RFC] ARM OMAP4: enable DSS by default

This patch removes the anyway default reset setting of HW_AUTO in favour of
SW_WKUP. So the DSS Module gets enabled and you gain full register access.
 arch/arm/mach-omap/omap4_clock.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-omap/omap4_clock.c b/arch/arm/mach-omap/omap4_clock.c
index 0621fd3..72335d9 100644
--- a/arch/arm/mach-omap/omap4_clock.c
+++ b/arch/arm/mach-omap/omap4_clock.c
@@ -375,8 +375,8 @@ void omap4_enable_all_clocks(void)
 	/* Check for DSS Clocks */
 	while ((__raw_readl(0x4A009100) & 0xF00) != 0xE00)
-	/* Set HW_AUTO transition mode */
-	sr32(CM_DSS_CLKSTCTRL, 0, 32, 0x3);
+	/* Set SW_WKUP to enable DSS Module with full register access */
+	sr32(CM_DSS_CLKSTCTRL, 0, 32, 0x2);
 	/* Enable SGX clocks */
 	sr32(CM_SGX_CLKSTCTRL, 0, 32, 0x2);

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