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ARM: tegra: only enable SCU on Tegra20

PATCH New Stephen Warren 2 participants 3 messages May 23, 2013 – Jun 4, 2013

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Arm (32-bit) Tegra architecture support
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Stephen Warren

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#0 lore raw

PATCH 1/1 ARM: tegra: only enable SCU on Tegra20

From: Tom Warren <[email protected]>

The non-SPL build of U-Boot on Tegra only runs on a single CPU, and hence there is no need to enable the SCU when running U-Boot. If an SMP OS is booted, and it needs the SCU enabled, it will enable the SCU itself. U-Boot doing so is redundant.

The one exception is Tegra20, where an enabled SCU is required for some aspects of PCIe to work correctly.

Some Tegra SoCs contain CPUs without a software-controlled SCU. In this case, attempting to turn it on actively causes problems. This is the case for Tegra114. For example, when running Linux, the first (or at least some very early) user-space process will trigger the following kernel message:

Unhandled fault: imprecise external abort (0x406) at 0x00000000

This is typically accompanied by that process receving a fatal signal, and exiting. Since this process is usually pid 1, this causes total system boot failure.

Signed-off-by Tom Warren <[email protected]>
[swarren, fleshed out description, ported to upstream chipid APIs]
Signed-off-by Stephen Warren <[email protected]>
---
 arch/arm/cpu/tegra-common/ap.c |    4 ++++
 1 file changed, 4 insertions(+)
arch/arm/cpu/tegra-common/ap.c +4 -0
index e099683..9e6d51d 100644
@@ -109,6 +109,10 @@ static void enable_scu(void)
 	struct scu_ctlr *scu = (struct scu_ctlr *)NV_PA_ARM_PERIPHBASE;
 	u32 reg;
 
+	/* Only enable the SCU on T20/T25 */
+	if (tegra_get_chip() != CHIPID_TEGRA20)
+		return;
+
 	/* If SCU already setup/enabled, return */
 	if (readl(&scu->scu_ctrl) & SCU_CTRL_ENABLE)
 		return;
Signature · 1 line
1.7.10.4
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#1 lore raw

PATCH 1/1 ARM: tegra: only enable SCU on Tegra20

Quoted 16 lines · Stephen Warren

From: Tom Warren <[email protected]>

The non-SPL build of U-Boot on Tegra only runs on a single CPU, and hence there is no need to enable the SCU when running U-Boot. If an SMP OS is booted, and it needs the SCU enabled, it will enable the SCU itself. U-Boot doing so is redundant.

The one exception is Tegra20, where an enabled SCU is required for some aspects of PCIe to work correctly.

Some Tegra SoCs contain CPUs without a software-controlled SCU. In this case, attempting to turn it on actively causes problems. This is the case for Tegra114. For example, when running Linux, the first (or at least some very early) user-space process will trigger the following kernel message:

Quoted 5 lines

Unhandled fault: imprecise external abort (0x406) at 0x00000000

This is typically accompanied by that process receving a fatal signal, and exiting. Since this process is usually pid 1, this causes total system boot failure.

Tom, is this patch OK? It's a rather critical bug-fix for Tegra114, so I'd like to make sure it gets into the upcoming release. Thanks.

#2 lore raw

PATCH 1/1 ARM: tegra: only enable SCU on Tegra20

Sorry, my BW is being used up by internal projects. I'll pull it down, apply/build/test in u-boot-tegra/next, and then I can send a PR to Albert if you think it needs to move higher up right away.

Tom

Quoted 25 lines

-----Original Message-----
From: Stephen Warren [mailto:swarren at wwwdotorg.org]
Sent: Tuesday, June 04, 2013 12:34 PM
To: Tom Warren
Cc: u-boot at lists.denx.de; Simon Glass; Stephen Warren
Subject: Re: [U-Boot] [PATCH] ARM: tegra: only enable SCU on Tegra20

Quoted 17 lines · Stephen Warren

From: Tom Warren <[email protected]>

The non-SPL build of U-Boot on Tegra only runs on a single CPU, and hence there is no need to enable the SCU when running U-Boot. If an SMP OS is booted, and it needs the SCU enabled, it will enable the SCU itself. U-Boot doing so is redundant.

The one exception is Tegra20, where an enabled SCU is required for some aspects of PCIe to work correctly.

Some Tegra SoCs contain CPUs without a software-controlled SCU. In this case, attempting to turn it on actively causes problems. This is the case for Tegra114. For example, when running Linux, the first (or at least some very early) user-space process will trigger the following kernel
message:

Quoted 8 lines
Quoted 5 lines

Unhandled fault: imprecise external abort (0x406) at 0x00000000

This is typically accompanied by that process receving a fatal signal, and exiting. Since this process is usually pid 1, this causes total system boot failure.

Tom, is this patch OK? It's a rather critical bug-fix for Tegra114, so I'd like to make sure it gets into the upcoming release. Thanks.

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