[PATCH v2] i2c: mv64xxx: continue probe when clock-frequency is missing

[PATCH v2] i2c: mv64xxx: continue probe when clock-frequency is missing

[Chen-Yu Tsai]

The "clock-frequency" DT property is listed as optional, However,
the current code stores the return value of of_property_read_u32 in
the return code of mv64xxx_of_config, but then forgets to clear it
after setting the default value of "clock-frequency". It is then
passed out to the main probe function, resulting in a probe failure
when "clock-frequency" is missing.

This patch checks and then throws away the return value of
of_property_read_u32, instead of storing it and having to clear it
afterwards.

This issue was discovered after the property was removed from all
sunxi DTs.

Fixes: 4c730a06c19bb ("i2c: mv64xxx: Set bus frequency to 100kHz if clock-frequency is not provided")
Signed-off-by: Chen-Yu Tsai <wens-jdAy2FN1RRM@public.gmane.org>
Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Acked-by: Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>
Acked-by: Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
---
Changes in v2:

 - Added Fixes tag, and Acked-bys from Andrew and Maxime.
 - Slightly refined commit message to be clear what we're throwing away.
---
 drivers/i2c/busses/i2c-mv64xxx.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
index 6dc5ded..2f64273 100644
--- a/drivers/i2c/busses/i2c-mv64xxx.c
+++ b/drivers/i2c/busses/i2c-mv64xxx.c
@@ -746,8 +746,7 @@ mv64xxx_of_config(struct mv64xxx_i2c_data *drv_data,
 	}
 	tclk = clk_get_rate(drv_data->clk);
 
-	rc = of_property_read_u32(np, "clock-frequency", &bus_freq);
-	if (rc)
+	if (of_property_read_u32(np, "clock-frequency", &bus_freq))
 		bus_freq = 100000; /* 100kHz by default */
 
 	if (!mv64xxx_find_baud_factors(bus_freq, tclk,
-- 
2.1.0

Re: [PATCH v2] i2c: mv64xxx: continue probe when clock-frequency is missing

[Wolfram Sang]

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On Mon, Sep 01, 2014 at 10:28:13PM +0800, Chen-Yu Tsai wrote:
> The "clock-frequency" DT property is listed as optional, However,
> the current code stores the return value of of_property_read_u32 in
> the return code of mv64xxx_of_config, but then forgets to clear it
> after setting the default value of "clock-frequency". It is then
> passed out to the main probe function, resulting in a probe failure
> when "clock-frequency" is missing.
> 
> This patch checks and then throws away the return value of
> of_property_read_u32, instead of storing it and having to clear it
> afterwards.
> 
> This issue was discovered after the property was removed from all
> sunxi DTs.

Hmm, I don't like that removal. Probably I should take care that this
property is not "optional" but "recommended". The default value is
depending on the driver, mostly because of historic reasons. It is
definately better to explicitly state it. Despite all that...

> 
> Fixes: 4c730a06c19bb ("i2c: mv64xxx: Set bus frequency to 100kHz if clock-frequency is not provided")
> Signed-off-by: Chen-Yu Tsai <wens-jdAy2FN1RRM@public.gmane.org>
> Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Acked-by: Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>
> Acked-by: Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>

Applied to for-current, thanks!


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