Re: [PATCH v2 2/3] fpga: zynq: Add support for encrypted bitstreams

From: Michal Simek
Date: Tue Feb 21 2017 - 08:55:43 EST


On 20.2.2017 21:55, mdf@xxxxxxxxxx wrote:
> From: Moritz Fischer <mdf@xxxxxxxxxx>
>
> Add support for encrypted bitstreams. For this to work the system
> must be booted in secure mode.
>
> In order for on-the-fly decryption to work, the PCAP clock rate
> needs to be lowered via the PCAP_RATE_EN bit.
>
> Signed-off-by: Moritz Fischer <mdf@xxxxxxxxxx>
> Cc: Alan Tull <atull@xxxxxxxxxx>
> Cc: Michal Simek <michal.simek@xxxxxxxxxx>
> Cc: SÃren Brinkmann <soren.brinkmann@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-fpga@xxxxxxxxxxxxxxx
> ---
>
> Changes from v1:
> - Renamed flag from FPGA_MGR_DECRYPT_BITSTREAM->FPGA_MGR_ENCRYPTED_BITSTREAM
>
> ---
> drivers/fpga/zynq-fpga.c | 28 +++++++++++++++++++++++++---
> 1 file changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/fpga/zynq-fpga.c b/drivers/fpga/zynq-fpga.c
> index 34cb981..70b15b3 100644
> --- a/drivers/fpga/zynq-fpga.c
> +++ b/drivers/fpga/zynq-fpga.c
> @@ -72,6 +72,10 @@
> #define CTRL_PCAP_PR_MASK BIT(27)
> /* Enable PCAP */
> #define CTRL_PCAP_MODE_MASK BIT(26)
> +/* Lower rate to allow decrypt on the fly */
> +#define CTRL_PCAP_RATE_EN_MASK BIT(25)
> +/* System booted in secure mode */
> +#define CTRL_SEC_EN_MASK BIT(7)
>
> /* Miscellaneous Control Register bit definitions */
> /* Internal PCAP loopback */
> @@ -266,6 +270,17 @@ static int zynq_fpga_ops_write_init(struct fpga_manager *mgr,
> if (err)
> return err;
>
> + /* check if bitstream is encrypted & and system's still secure */
> + if (info->flags & FPGA_MGR_ENCRYPTED_BITSTREAM) {
> + ctrl = zynq_fpga_read(priv, CTRL_OFFSET);
> + if (!(ctrl & CTRL_SEC_EN_MASK)) {
> + dev_err(&mgr->dev,
> + "System not secure, can't use crypted bitstreams\n");
> + err = -EINVAL;
> + goto out_err;
> + }
> + }
> +
> /* don't globally reset PL if we're doing partial reconfig */
> if (!(info->flags & FPGA_MGR_PARTIAL_RECONFIG)) {
> if (!zynq_fpga_has_sync(buf, count)) {
> @@ -337,12 +352,19 @@ static int zynq_fpga_ops_write_init(struct fpga_manager *mgr,
>
> /* set configuration register with following options:
> * - enable PCAP interface
> - * - set throughput for maximum speed
> + * - set throughput for maximum speed (if bistream not crypted)
> * - set CPU in user mode
> */
> ctrl = zynq_fpga_read(priv, CTRL_OFFSET);
> - zynq_fpga_write(priv, CTRL_OFFSET,
> - (CTRL_PCAP_PR_MASK | CTRL_PCAP_MODE_MASK | ctrl));
> + if (info->flags & FPGA_MGR_ENCRYPTED_BITSTREAM)
> + zynq_fpga_write(priv, CTRL_OFFSET,
> + (CTRL_PCAP_PR_MASK | CTRL_PCAP_MODE_MASK
> + | CTRL_PCAP_RATE_EN_MASK | ctrl));
> + else
> + zynq_fpga_write(priv, CTRL_OFFSET,
> + (CTRL_PCAP_PR_MASK | CTRL_PCAP_MODE_MASK
> + | ctrl));
> +
>
> /* We expect that the command queue is empty right now. */
> status = zynq_fpga_read(priv, STATUS_OFFSET);
>

Acked-by: Michal Simek <michal.simek@xxxxxxxxxx>

Thanks,
Michal