On Wed, Jul 03, 2013 at 04:44:09PM +0200, Arnd Bergmann wrote: > On Wednesday 03 July 2013, Christian Ruppert wrote: > > On Wed, Jul 03, 2013 at 04:20:03PM +0200, Arnd Bergmann wrote: > > > On Wednesday 03 July 2013, Christian Ruppert wrote: > > > > On Wed, Jul 03, 2013 at 01:43:11PM +0200, Arnd Bergmann wrote: > > > > > On Wednesday 26 June 2013, Wolfram Sang wrote: > > > > > > On Wed, Jun 26, 2013 at 10:55:06AM +0200, Christian Ruppert wrote: > > > > > > > This patch makes the SDA hold time configurable through device tree. > > > > > > > > > > > > > > Signed-off-by: Christian Ruppert <christian.ruppert@xxxxxxxxxx> > > > > > > > Signed-off-by: Pierrick Hascoet <pierrick.hascoet@xxxxxxxxxx> > > > > > > > > > > > > Applied to for-next, thanks for keeping at it and providing lots of > > > > > > useful information. Much appreciated! > > > > > > > > > > Sorry, but I got a regression that I didn't find reported elsewhere > > > > > so far, even though it breaks a lot of the ARM defconfig builds: > > > > > > > > > > drivers/built-in.o: In function `dw_i2c_probe': > > > > > /git/arm-soc/drivers/i2c/busses/i2c-designware-platdrv.c:125: undefined reference to `__udivdi3' > > > > > > > > > > I suspect you want something like the change below. > > > > > > > > This looks similar to a patch Vincent Stehle submitted yesterday, see > > > > https://lkml.org/lkml/2013/7/2/145 > > > > > > Thanks for the link. Actually his patch looks wrong to me, because > > > > > > dev->sda_hold_time = div_u64((u64)ic_clk * ht + 500000, 1000000); > > > > > > assigns the division remainder to sda_hold_time, not the quotient. > > > > Hrmmm... At least when I tested it this morning on an ARC architecture > > it worked as intended and returned the quotient. Does that mean we have > > an issue with this function on ARC? Can anyone who knows these functions > > better than I comment? > > ARC just uses the generic version of div_u64, which is defined in lib/div64.c. > > I suspect that the division remainder just happens to work well enough for > you to not cause any run-time error. You could try adding a printk > in that function to show the values you get on ARC. That's what I did and they were identical to the original values calculated with /. I just looked at include/linux/math64.h and found the following comment: /** * div_u64 - unsigned 64bit divide with 32bit divisor * * This is the most common 64bit divide and should be used if possible, * as many 32bit archs can optimize this variant better than a full 64bit * divide. */ Although this doesn't explicitly state what the function returns to me this sounds more like the quotient is returned rather than the remainder? -- Christian Ruppert , <christian.ruppert@xxxxxxxxxx> /| Tel: +41/(0)22 816 19-42 //| 3, Chemin du Pré-Fleuri _// | bilis Systems CH-1228 Plan-les-Ouates -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
