[PATCH] ARM: tegra: fix U16 divider range check
From: pgaikwad@nvidia.com (Prashant Gaikwad)
Date: 2012-07-25 06:42:44
Also in:
linux-tegra
On Wednesday 25 July 2012 04:20 AM, Stephen Warren wrote:
From: Stephen Warren<redacted> A U16 divider can divide a clock by 1..64K. However, the range-check in clk_div16_get_divider() limited the range to 1..256. Fix this. NVIDIA's downstream kernels already have the fixed range-check. In practice this is a problem on Whistler's I2C bus, which uses a bus clock rate of 100KHz (rather than the more common 400KHz on Tegra boards), which requires a HW module clock of 8*100KHz. The parent clock is 216MHz, leading to a desired divider of 270. Prior to conversion to the common clock framework, this range error was somehow ignored/irrelevant and caused no problems. However, the common clock framework evidently has more rigorous error-checking, so this failure causes the I2C bus to fail to operate correctly. Signed-off-by: Stephen Warren<redacted>
Thanks Stephen!! Verified on Cardhu and Ventana with common clock framework patches.
quoted hunk ↗ jump to hunk
--- arch/arm/mach-tegra/tegra2_clocks.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)diff --git a/arch/arm/mach-tegra/tegra2_clocks.c b/arch/arm/mach-tegra/tegra2_clocks.c index a703844..83ccb85 100644 --- a/arch/arm/mach-tegra/tegra2_clocks.c +++ b/arch/arm/mach-tegra/tegra2_clocks.c@@ -223,7 +223,7 @@ static int clk_div16_get_divider(unsigned long parent_rate, unsigned long rate) if (divider_u16 - 1< 0) return 0; - if (divider_u16 - 1> 255) + if (divider_u16 - 1> 0xFFFF) return -EINVAL; return divider_u16 - 1;