On Fri, May 15, 2015 at 03:48:38PM +0800, Chen-Yu Tsai wrote:

On Fri, May 15, 2015 at 3:43 PM, Maxime Ripard
[off-list ref] wrote:

quoted

On Thu, May 14, 2015 at 05:12:07PM +0800, Chen-Yu Tsai wrote:

quoted

On Sat, May 2, 2015 at 7:24 PM, Maxime Ripard
[off-list ref] wrote:

quoted

Some clocks start incrementing the m factor at 0. Add a parameter to handle
it just like we did for the N factor.

Since the behaviour until now was to assume that the m factor was starting
at 1, we also need to fix the other users.

Signed-off-by: Maxime Ripard <redacted>
---
 drivers/clk/sunxi/clk-factors.c    | 11 ++++++++++-
 drivers/clk/sunxi/clk-factors.h    |  2 ++
 drivers/clk/sunxi/clk-mod0.c       |  2 ++
 drivers/clk/sunxi/clk-sun8i-mbus.c |  2 ++
 drivers/clk/sunxi/clk-sun9i-core.c |  6 ++++++
 drivers/clk/sunxi/clk-sunxi.c      | 10 ++++++++++
 6 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/sunxi/clk-factors.c b/drivers/clk/sunxi/clk-factors.c
index 8c20190a3e9f..100a711c3e3d 100644
--- a/drivers/clk/sunxi/clk-factors.c
+++ b/drivers/clk/sunxi/clk-factors.c

@@ -56,15 +56,24 @@ static unsigned long clk_factors_recalc_rate(struct clk_hw *hw,
        /* Get each individual factor if applicable */
        if (config->nwidth != SUNXI_FACTORS_NOT_APPLICABLE)
                n = FACTOR_GET(config->nshift, config->nwidth, reg);
+
        if (config->kwidth != SUNXI_FACTORS_NOT_APPLICABLE)
                k = FACTOR_GET(config->kshift, config->kwidth, reg);
+
        if (config->mwidth != SUNXI_FACTORS_NOT_APPLICABLE)
                m = FACTOR_GET(config->mshift, config->mwidth, reg);
+       else
+               /* Make sure we don't get a division by zero */
+               m = 1;

What happens when mwidth is valid, m_start = 0, and m = 0?

That's a very good question. A division by zero in the kernel, I'd
say.

But I don't think we can end up in such a case today, and it's
somewhat expected that it will happen, and no clock have looked at can
actually end up in such a case.

It's possible if the bootloader left the clock in an invalid state.
How about just returning 0, indicating an invalid rate, early?

The value set in the register might be zero, but that will always
really mean 1, either through m_start or m_zero. That would be a bug
in the driver itself.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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