Re: [U-Boot] [PATCH 1/3] ARM: implement some Cortex-A9 errata workarounds

On Tue, Feb 26, 2013 at 2:28 PM, Stephen Warren swarren@wwwdotorg.org wrote:

From: Stephen Warren swarren@nvidia.com

Various errata exist in the Cortex-A9 CPU, and may be worked around by setting some bits in a CP15 diagnostic register. Add code to implement the workarounds, enabled by new CONFIG_ options.

This code was taken from the Linux kernel, v3.8, arch/arm/mm/proc-v7.S, and modified to remove the logic to conditionally apply the WAR (since we know exactly which CPU we're running on given the U-Boot configuration), and use r0 instead of r10 for consistency with the rest of U-Boot's cpu_init_cp15().

Signed-off-by: Stephen Warren swarren@nvidia.com

Acked-by: Simon Glass sjg@chromium.org

Good to have. Although I wonder why we wouldn't want to probe it in U-Boot as with Linux?

---

README | 10 ++++++++++ arch/arm/cpu/armv7/start.S | 19 +++++++++++++++++++ 2 files changed, 29 insertions(+)

diff --git a/README b/README index d8cb394..f2b1c88 100644 --- a/README +++ b/README @@ -485,6 +485,16 @@ The following options need to be configured: Thumb2 this flag will result in Thumb2 code generated by GCC.

•           CONFIG_ARM_ERRATA_742230
  

•           CONFIG_ARM_ERRATA_743622
  

•           CONFIG_ARM_ERRATA_751472
  

•           If set, the workarounds for these ARM errata are applied early
  

•           during U-Boot startup. Note that these options force the
  

•           workarounds to be applied; no CPU-type/version detection
  

•           exists, unlike the similar options in the Linux kernel. Do not
  

•           set these options unless they apply!
  

• Linux Kernel Interface: CONFIG_CLOCKS_IN_MHZ

diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S index 6b59529d..30f02d3 100644 --- a/arch/arm/cpu/armv7/start.S +++ b/arch/arm/cpu/armv7/start.S @@ -309,6 +309,25 @@ ENTRY(cpu_init_cp15) orr r0, r0, #0x00001000 @ set bit 12 (I) I-cache #endif mcr p15, 0, r0, c1, c0, 0

+#ifdef CONFIG_ARM_ERRATA_742230

•   mrc     p15, 0, r0, c15, c0, 1  @ read diagnostic register
  

•   orr     r0, r0, #1 << 4         @ set bit #4
  

•   mcr     p15, 0, r0, c15, c0, 1  @ write diagnostic register
  

+#endif

+#ifdef CONFIG_ARM_ERRATA_743622

•   mrc     p15, 0, r0, c15, c0, 1  @ read diagnostic register
  

•   orr     r0, r0, #1 << 6         @ set bit #6
  

•   mcr     p15, 0, r0, c15, c0, 1  @ write diagnostic register
  

+#endif

+#ifdef CONFIG_ARM_ERRATA_751472

•   mrc     p15, 0, r0, c15, c0, 1  @ read diagnostic register
  

•   orr     r0, r0, #1 << 11        @ set bit #11
  

•   mcr     p15, 0, r0, c15, c0, 1  @ write diagnostic register
  

+#endif

•   mov     pc, lr                  @ back to my caller
  

ENDPROC(cpu_init_cp15)

-- 1.7.10.4