David Hendricks (dhendrix@chromium.org) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/3121
-gerrit
commit 9cd5ebe34dae69febebce240ca0123d4f4f9d2ec Author: David Hendricks dhendrix@chromium.org Date: Mon Apr 22 16:03:11 2013 -0700
exynos5250: ungate the product ID register
This makes sure that the product ID (PRO_ID) register can be read when the OS kernel is figuring out what kind of CPU it's running on.
For historical reference, the original U-Boot code seems to have worked basically by accident here. The hardware has a quirk where by reading the value before gating the IP block keeps the value persistent. U-Boot reads the chip ID early on to distinguish between chip family, but we do not mix code the same way so we do not read the chip ID. Since the value has been read before the clock gating happens, the value remains available for the kernel to use during the decompression stage. We don't want to rely on that behavior when using coreboot. Instead the kernel should gate unused IPs.
(credit to Gabe for finding symptom in the kernel)
Change-Id: Iaa21e6e718b9000b5558f568020f393779fd208e Signed-off-by: Gabe Black gabeblack@chromium.org Signed-off-by: David Hendricks dhendrix@chromium.org --- src/cpu/samsung/exynos5250/clock_init.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/src/cpu/samsung/exynos5250/clock_init.c b/src/cpu/samsung/exynos5250/clock_init.c index c94cadf..0989b88 100644 --- a/src/cpu/samsung/exynos5250/clock_init.c +++ b/src/cpu/samsung/exynos5250/clock_init.c @@ -416,7 +416,12 @@ void clock_gate(void) CLK_SPI2_MASK | CLK_SPI0_MASK);
- /* CLK_GATE_IP_PERIS */ + /* + * CLK_GATE_IP_PERIS + * Note: Keep CHIPID_APBIF ungated to ensure reading the product ID + * register (PRO_ID) works correctly when the OS kernel determines + * which chip it is running on. + */ clrbits_le32(&clk->gate_ip_peris, CLK_RTC_MASK | CLK_TZPC9_MASK | CLK_TZPC8_MASK | @@ -427,8 +432,7 @@ void clock_gate(void) CLK_TZPC3_MASK | CLK_TZPC2_MASK | CLK_TZPC1_MASK | - CLK_TZPC0_MASK | - CLK_CHIPID_MASK); + CLK_TZPC0_MASK);
/* CLK_GATE_BLOCK */ clrbits_le32(&clk->gate_block, CLK_ACP_MASK);