Re: [PATCH v10] i2c-designware: make SDA hold time configurable
On 06/26/2013 02:25 PM, Christian Ruppert wrote: > This patch makes the SDA hold time configurable through device tree. > > Signed-off-by: Christian Ruppert > Signed-off-by: Pierrick Hascoet > --- > .../devicetree/bindings/i2c/i2c-designware.txt | 15 +++ > arch/arc/boot/dts/abilis_tb100_dvk.dts | 10 +- > arch/arc/boot/dts/abilis_tb101_dvk.dts | 10 +- > drivers/i2c/busses/i2c-designware-core.c | 13 + > drivers/i2c/busses/i2c-designware-core.h |1 + > drivers/i2c/busses/i2c-designware-platdrv.c| 10 ++ > 6 files changed, 49 insertions(+), 10 deletions(-) Acked-by: Vineet Gupta for arch/arc bits -Vineet ___ devicetree-discuss mailing list devicetree-discuss@lists.ozlabs.org https://lists.ozlabs.org/listinfo/devicetree-discuss
Re: [PATCH v10] i2c-designware: make SDA hold time configurable
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 > > Signed-off-by: Pierrick Hascoet > > 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. Signed-off-by: Arnd Bergmann diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c index def79b5..57e3a07 100644 --- a/drivers/i2c/busses/i2c-designware-platdrv.c +++ b/drivers/i2c/busses/i2c-designware-platdrv.c @@ -119,10 +119,13 @@ static int dw_i2c_probe(struct platform_device *pdev) if (pdev->dev.of_node) { u32 ht = 0; u32 ic_clk = dev->get_clk_rate_khz(dev); + u64 hold_time; of_property_read_u32(pdev->dev.of_node, "i2c-sda-hold-time-ns", &ht); - dev->sda_hold_time = ((u64)ic_clk * ht + 50) / 100; + hold_time = (u64)ic_clk * ht + 50; + do_div(hold_time, 100); + dev->sda_hold_time = hold_time; } dev->functionality = ___ devicetree-discuss mailing list devicetree-discuss@lists.ozlabs.org https://lists.ozlabs.org/listinfo/devicetree-discuss
Re: [PATCH v10] i2c-designware: make SDA hold time configurable
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 > > > > Signed-off-by: Pierrick Hascoet > > > > > > 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 + 50, 100); assigns the division remainder to sda_hold_time, not the quotient. Arnd > > Signed-off-by: Arnd Bergmann > > > > diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c > > b/drivers/i2c/busses/i2c-designware-platdrv.c > > index def79b5..57e3a07 100644 > > --- a/drivers/i2c/busses/i2c-designware-platdrv.c > > +++ b/drivers/i2c/busses/i2c-designware-platdrv.c > > @@ -119,10 +119,13 @@ static int dw_i2c_probe(struct platform_device *pdev) > > if (pdev->dev.of_node) { > > u32 ht = 0; > > u32 ic_clk = dev->get_clk_rate_khz(dev); > > + u64 hold_time; > > > > of_property_read_u32(pdev->dev.of_node, > > "i2c-sda-hold-time-ns", &ht); > > - dev->sda_hold_time = ((u64)ic_clk * ht + 50) / 100; > > + hold_time = (u64)ic_clk * ht + 50; > > + do_div(hold_time, 100); > > + dev->sda_hold_time = hold_time; > > } > > > > dev->functionality = ___ devicetree-discuss mailing list devicetree-discuss@lists.ozlabs.org https://lists.ozlabs.org/listinfo/devicetree-discuss
Re: [PATCH v10] i2c-designware: make SDA hold time configurable
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 > > > > > > Signed-off-by: Pierrick Hascoet > > > > > > > > > > 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 + 50, 100); > > > > 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. Arnd ___ devicetree-discuss mailing list devicetree-discuss@lists.ozlabs.org https://lists.ozlabs.org/listinfo/devicetree-discuss
Re: [PATCH v10] i2c-designware: make SDA hold time configurable
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 > > > > > > Signed-off-by: Pierrick Hascoet > > > > > > > > > > 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 + 50, 100); > > > > 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. Arnd ___ devicetree-discuss mailing list devicetree-discuss@lists.ozlabs.org https://lists.ozlabs.org/listinfo/devicetree-discuss
Re: [PATCH v10] i2c-designware: make SDA hold time configurable
On Wednesday 03 July 2013, Stehle Vincent-B46079 wrote: > > From: Christian Ruppert [mailto:christian.rupp...@abilis.com] > (..) > > Although this doesn't explicitly state what the function returns to me > > this sounds more like the quotient is returned rather than the remainder? > > Hi, > > Yes div_u64() returns the quotient. > > It is defined in linux/math64.h as: > > static inline u64 div_u64(u64 dividend, u32 divisor) > { > u32 remainder; > return div_u64_rem(dividend, divisor, &remainder); > } > > The remainder is probably fully optimized out. Ah, you are right, sorry for the confusion on my part. I thought you had used do_div() rather than div_u64(). Everything's fine then, feel free to add my Acked-by: Arnd Bergmann to your patch. Arnd ___ devicetree-discuss mailing list devicetree-discuss@lists.ozlabs.org https://lists.ozlabs.org/listinfo/devicetree-discuss