Re: [PATCH] zynq-fpga: Only route PR via PCAP when required
From: Moritz Fischer
Date: Tue Oct 23 2018 - 07:04:52 EST
On Tue, Oct 23, 2018 at 10:53:50AM +0000, Mike Looijmans wrote:
> On 23-10-18 11:01, Moritz Fischer wrote:
> > Hi Mike,
> > seems like a good usecase (though uncommon), question below
> Usecases for ICAP:
> - It's considerably faster than PCAP
> - Self-repairing logic (e.g. single-event upsets)
> - Being programmed from a remote FPGA
> - Programming through another bus (e.g. PCIe)
Yeah, I wasn't saying it's a bad usecase, just not super common :)
> > On Tue, Oct 23, 2018 at 08:31:19AM +0200, Mike Looijmans wrote:
> >> The Xilinx Zynq FPGA driver takes ownership of the PR interface, making
> >> it impossible to use the ICAP interface for partial reconfiguration.
> >> This patch changes the driver to only activate PR over PCAP while the
> >> device is actively being accessed by the driver for programming.
> >> This allows both PCAP and ICAP interfaces to be used for PR.
> >> Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
> >> ---
> >> drivers/fpga/zynq-fpga.c | 4 ++++
> >> 1 file changed, 4 insertions(+)
> >> diff --git a/drivers/fpga/zynq-fpga.c b/drivers/fpga/zynq-fpga.c
> >> index 3110e00..f6c205a 100644
> >> --- a/drivers/fpga/zynq-fpga.c
> >> +++ b/drivers/fpga/zynq-fpga.c
> >> @@ -497,6 +497,10 @@ static int zynq_fpga_ops_write_complete(struct fpga_manager *mgr,
> >> int err;
> >> u32 intr_status;
> >> + /* Release 'PR' control back to the ICAP */
> >> + zynq_fpga_write(priv, CTRL_OFFSET,
> >> + zynq_fpga_read(priv, CTRL_OFFSET) & ~CTRL_PCAP_PR_MASK);
> >> +
> > Shouldn't that be after the below stanza that enables the clock?
> I'm actually not sure, and I did not encounter any problems while testing
> this, but it's easier to just move it than to find out, so I'll go for "yes,
> let's enable the clock first".
> I'll await a bit more feedback and post a v2 for that.
Ok, I had suspected you tested it and probably didn't run into issues,
but just wanted to make sure we think about it. If you don't mind, swap
it around as I suggested just to be safe.
With that change feel free to add my Reviewed-by: Moritz Fischer
<mdf@xxxxxxxxxx> in your v2.
Thanks for the patch,