On Wed, Apr 27, 2016 at 9:43 AM, Viresh Kumar <[email protected]> wrote: > On 25-04-16, 15:35, Andy Shevchenko wrote: >> There are several changes are done here: >> >> - Convert the property to be in bytes >> >> Besides this is common practice for such property the use of a value in bytes >> much more convenient than handling the encoded value. >> >> - Rename data_width to data-width in the device tree bindings >> >> - While here, replace dwc_fast_ffs() by __ffs() >> >> The change leaves the support for old format as well just in case someone >> will >> use a newer kernel with an old device tree blob. >> >> Signed-off-by: Andy Shevchenko <[email protected]> >> --- >> Documentation/devicetree/bindings/dma/snps-dma.txt | 6 ++-- >> arch/arc/boot/dts/abilis_tb10x.dtsi | 2 +- >> arch/arm/boot/dts/spear13xx.dtsi | 4 +-- >> drivers/dma/dw/core.c | 42 >> ++++++---------------- >> drivers/dma/dw/platform.c | 5 ++- >> include/linux/platform_data/dma-dw.h | 2 +- >> 6 files changed, 21 insertions(+), 40 deletions(-) >> >> diff --git a/Documentation/devicetree/bindings/dma/snps-dma.txt >> b/Documentation/devicetree/bindings/dma/snps-dma.txt >> index c99c1ff..544b9b9 100644 >> --- a/Documentation/devicetree/bindings/dma/snps-dma.txt >> +++ b/Documentation/devicetree/bindings/dma/snps-dma.txt >> @@ -13,8 +13,8 @@ Required properties: >> - chan_priority: priority of channels. 0 (default): increase from chan >> 0->n, 1: >> increase from chan n->0 >> - block_size: Maximum block size supported by the controller >> -- data_width: Maximum data width supported by hardware per AHB master >> - (0 - 8bits, 1 - 16bits, ..., 5 - 256bits) >> +- data-width: Maximum data width supported by hardware per AHB master >> + (in bytes, power of 2) >> >> >> Optional properties: >> @@ -38,7 +38,7 @@ Example: >> chan_allocation_order = <1>; >> chan_priority = <1>; >> block_size = <0xfff>; >> - data_width = <3 3>; >> + data-width = <8 8>; >> }; > > You broke backward compatibility with earlier DTs.
How? > > What's backward compatibility ? > > Consider that the DT from an earlier version of kernel is part of the bootrom > of > a SoC. Now that bootrom should work just fine with any new kernel version. > i.e. > old DT + new kernels should always work. Yes, the property name is slightly different as meaning. If we find data-width property driver will use it, otherwise it takes old name and converts variable to be in bytes in the driver. -- With Best Regards, Andy Shevchenko
