On Mon, Oct 28, 2013 at 10:13:28PM +0100, Tomasz Figa wrote: > Hi Soren, > > On Thursday 10 of October 2013 10:10:17 Soren Brinkmann wrote: > > In some use cases Zynq's FPGA clocks are used as static clock > > generators for IP in the FPGA part of the SOC for which no Linux driver > > exists and would control those clocks. To avoid automatic > > gating of these clocks in such cases a new property - fclk-enable - is > > added to the clock controller's DT description to accomodate such use > > cases. It's value is a bitmask, where a set bit results in enabling > > the corresponding FCLK through the clkc. > > > > FPGA clocks are handled following the rules below: > > > > If an FCLK is not enabled by bootloaders, that FCLK will be disabled in > > Linux. Drivers can enable and control it through the CCF as usual. > > > > If an FCLK is enabled by bootloaders AND the corresponding bit in the > > 'fclk-enable' DT property is set, that FCLK will be enabled by the clkc, > > resulting in an off by one reference count for that clock. Ensuring it > > will always be running. > > > > Signed-off-by: Soren Brinkmann <soren.brinkmann@xxxxxxxxxx> > > --- > > v2: > > - change default value for fclk-enable to '0' > > --- > > Documentation/devicetree/bindings/clock/zynq-7000.txt | 4 ++++ > > drivers/clk/zynq/clkc.c | 18 > > +++++++++++++++--- 2 files changed, 19 insertions(+), 3 deletions(-) > > > > diff --git a/Documentation/devicetree/bindings/clock/zynq-7000.txt > > b/Documentation/devicetree/bindings/clock/zynq-7000.txt index > > d99af878f5d7..11fdd146ec83 100644 > > --- a/Documentation/devicetree/bindings/clock/zynq-7000.txt > > +++ b/Documentation/devicetree/bindings/clock/zynq-7000.txt > > @@ -22,6 +22,10 @@ Required properties: > > Optional properties: > > - clocks : as described in the clock bindings > > - clock-names : as described in the clock bindings > > + - fclk-enable : Bit mask to enable FCLKs in cases no proper CCF > > Since it's a vendor specific property, it should include vendor prefix. The whole driver is vendor specific. Should there really be another prefix for that property? > > Also CCF is a Linux-specific implementation detail, which DT bindings > should not be involved into. If you really need to implement this using > this way, then at least property description should say something like > this: > > xlnx,fclk-enable : Bit mask of bits of fclk enable register that must > be statically enabled at boot-up time. Fair enough. I'll change the description > > However, I wonder why you can't simply define an FPGA block using a single > node, which would be a consumer to all the fclk clocks you need to enable > and then make a driver for it that would simply enable all clocks > specified in clocks property. Well, then we'd have a dummy driver that wouldn't fit into any subsystem and wouldn't do anything but enabling clocks. Seems much easier to handle it in this driver. Especially, since I hope that this is just a workaround and that the majority of use cases involves drivers for their soft-IP that simply uses the CCF. Sören -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
