Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> writes: > On Mon, 2016-01-25 at 07:32 +0000, Vineet Gupta wrote: >> On Monday 25 January 2016 12:55 AM, Mans Rullgard wrote: >> > From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> >> > >> > There are several changes are done here: >> > >> > - Convert the property to be in bytes >> > >> > Much more convenient than keeping encoded value. >> > >> > - Use one value for all AHB masters for now >> > >> > It seems in practice we have no controllers where masters have >> > different >> > data bus width, we still might return to distinct values when >> > there is a use >> > case. >> > >> > - Rename data_width to data-width in the device tree bindings. >> > >> > - While here, replace dwc_fast_ffs() by __ffs(). >> > >> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> >> > Signed-off-by: Mans Rullgard <mans@xxxxxxxxx> >> > --- >> > This patch changes the DT binding, so it should probably be amended >> > for >> > compatibility with old device trees. I've included it as is since >> > I think >> > the change as such is good. >> > --- >> > Documentation/devicetree/bindings/dma/snps-dma.txt | 5 ++- >> > arch/arc/boot/dts/abilis_tb10x.dtsi | 2 +- >> > arch/arm/boot/dts/spear13xx.dtsi | 4 +-- >> > drivers/dma/dw/core.c | 40 +++------- >> > ------------ >> > drivers/dma/dw/platform.c | 8 ++--- >> > drivers/dma/dw/regs.h | 2 +- >> > include/linux/platform_data/dma-dw.h | 5 ++- >> > 7 files changed, 16 insertions(+), 50 deletions(-) >> > >> > diff --git a/Documentation/devicetree/bindings/dma/snps-dma.txt >> > b/Documentation/devicetree/bindings/dma/snps-dma.txt >> > index c99c1ffac199..fe7f7710a6b4 100644 >> > --- a/Documentation/devicetree/bindings/dma/snps-dma.txt >> > +++ b/Documentation/devicetree/bindings/dma/snps-dma.txt >> > @@ -13,8 +13,7 @@ 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 (in bytes) >> >> To the reader this suggests a value truely byte granular, but code >> uses ffs >> implying that it is still power of 2. >> Can you mention this here (....in bytes, always power of 2). > > While this comment is good, I have still note that using non-power of 2 > values will not break anything. Least power of two number will be used > in that case. So, means I would suggest to replace 'always' by 'better > to be' or something like that. Although the code rounds down, the hardware actually works in powers of two, and it's better to document this. -- Måns Rullgård -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
