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https://github.com/brain-hackers/u-boot-brain
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77ef136950
Right now U-Boot supports the CONFIG_OLD_SUNXI_KERNEL_COMPAT option, which makes it go out of its way in limiting the selection of PLL clock frequencies and PMIC voltages in order not to upset outdated buggy sunxi-3.4 kernel releases. And if the CONFIG_OLD_SUNXI_KERNEL_COMPAT option is not set, then booting such old kernels exhibits various failures at runtime. This is very user unfriendly, and there were already several incidents when people wasted their time being hit by these runtime failures and trying to debug them. The right solution is not to add hacks and workarounds to the mainline U-Boot, but to fix these bugs in the sunxi-3.4 kernel. And in fact, the updated sunxi-3.4 kernels already exist. Still we need to follow the 'Principle of Least Surprise' and U-Boot needs to ensure that the old buggy kernels are not getting happily booted when the CONFIG_OLD_SUNXI_KERNEL_COMPAT option is not set. And this patch addresses this particular issue. This patch makes U-Boot store the 'compatibility revision' number in the top 4 bits of the machine id and pass it to the kernel. The old buggy kernels will fail to load with a very much googlable error message on the serial console (the "r1 = 0x100010bb" part of it): "Error: unrecognized/unsupported machine ID (r1 = 0x100010bb)" This error message can be documented in the linux-sunxi wiki with proper explanations about how to resolve this situation and where to get the necessary bugfixes for the sunxi-3.4 kernel. The fixed sunxi-3.4 kernels implement a revision compatibility check and clear the top 4 bits of the machine id if everything is alright. By accepting the machine id with the bits 31:28 set to 1, the sunxi-3.4 kernel effectively certifies that it has the PLL5 clock speed and AXP209 DCDC3 voltage fixes applied. It is still possible to set the CONFIG_OLD_SUNXI_KERNEL_COMPAT option in U-Boot if the user desires to use an outdated unpatched sunxi-3.4 kernel. Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com> Acked-by: Ian Campbell <ijc@hellion.org.uk> Acked-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
35 lines
846 B
C
35 lines
846 B
C
/*
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* (C) Copyright 2012-2013 Henrik Nordstrom <henrik@henriknordstrom.net>
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* (C) Copyright 2013 Luke Kenneth Casson Leighton <lkcl@lkcl.net>
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*
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* Configuration settings for the Allwinner A20 (sun7i) CPU
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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#ifndef __CONFIG_H
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#define __CONFIG_H
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/*
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* A20 specific configuration
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*/
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#define CONFIG_CLK_FULL_SPEED 912000000
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#ifdef CONFIG_USB_EHCI
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#define CONFIG_USB_EHCI_SUNXI
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#define CONFIG_USB_MAX_CONTROLLER_COUNT 2
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#endif
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#define CONFIG_ARMV7_PSCI 1
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#define CONFIG_ARMV7_SECURE_BASE SUNXI_SRAM_B_BASE
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#define CONFIG_SYS_CLK_FREQ 24000000
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#define CONFIG_TIMER_CLK_FREQ CONFIG_SYS_CLK_FREQ
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/*
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* Include common sunxi configuration where most the settings are
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*/
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#include <configs/sunxi-common.h>
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#define CONFIG_MACH_TYPE (4283 | ((CONFIG_MACH_TYPE_COMPAT_REV) << 28))
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#endif /* __CONFIG_H */
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