Messages in this thread | | | Date | Mon, 13 May 2013 18:21:13 +0200 | From | Sebastian Hesselbarth <> | Subject | Re: [PATCH RFC] clk: Introduce userspace clock driver |
| |
On 05/13/13 18:09, Sören Brinkmann wrote: > On Mon, May 13, 2013 at 09:21:35AM +0400, Mark Brown wrote: >> On Sun, May 12, 2013 at 12:05:04PM -0700, Sören Brinkmann wrote: >>> On Sun, May 12, 2013 at 06:33:44PM +0400, Mark Brown wrote: >>>> No, there's no confusion here - the clocks that are being exposed to >>>> userspace are the clocks which enter the FPGA. The driver or whatever >>>> that understands the FPGA can do what is needed to control them, >>>> including routing them on to subdevices it instantiates or exposing them >>>> to userspace. >> >>> Such a driver does not exist in general. >>> For some IP cores, Linux drivers do exist and then >>> they are supposed to directly use the CCF, IMHO, no need to expose >>> things to userspace in that case. >>> I'm trying to cover cases, in which there is no driver available/needed for >>> the FPGA design, other than some simple clock controls. >> >> You're not understanding the point here. If you've got a >> reprogrammmable FPGA you at least need some way to get the FPGA image in >> there. This driver is presumably responsible for instantiating whatever >> is needed to control what is on the FPGA, that could include punting the >> clocks to userspace if that's sane. > Well, that driver actually exists. But that just programs a bitstream > you give it to program. It does not know anything about the design it > programs and cannot make any kind of decision whether the clocks should > be userspace controlled or not.
Soeren,
what Mark wants to point out is that you add fabric clocks to the Xilinx driver instead. This way, you will have user-space controllable clocks but only if you loaded the xilinx driver first.
IIRC the fabric clock controller provided by Zynq _is_ always there and accessible from ARM CPUs. You just don't have a new generic driver allowing to poke with all clocks, but a xilinx only driver allowing you to set the (xilinx only) fabric clocks.
I've played with Zynq a while ago, did Xilinx mainline the bitfile driver already? If not, why don't you give it a shot?
Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |