Thread (3 messages) 3 messages, 2 authors, 2012-08-03
DORMANTno replies

[PATCH] ARM: tegra: fix U16 divider range check

From: Stephen Warren <hidden>
Date: 2012-08-03 18:01:51
Also in: linux-tegra

On 07/24/2012 04:50 PM, 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.
Applied to for-3.7/common-clk.
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