Re: [PATCH v10 1/8] usage documentation for FPGA manager core

[Moritz Fischer]

Hi Alan,

thanks for continuing to work on this :) A couple of minor nits ...

On Thu, Aug 13, 2015 at 10:37 AM,  <atull@xxxxxxxxxxxxxxxxxxxxx> wrote:
> From: Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx>
>
> Add a document on the new FPGA manager core.
>
> Signed-off-by: Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx>
> ---
> v9:  initial version where this patch was added
>
> v10: requested cleanups to formatting and otherwise
>      s/fpga/FPGA/g
>      rewrite implementation section to not reference socfpga.c by name
>      other rewrites
>      Moved to Documentation/fpga/
> ---
>  Documentation/fpga/fpga-mgr.txt |  171 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 171 insertions(+)
>  create mode 100644 Documentation/fpga/fpga-mgr.txt
>
> diff --git a/Documentation/fpga/fpga-mgr.txt b/Documentation/fpga/fpga-mgr.txt
> new file mode 100644
> index 0000000..c5259e4
> --- /dev/null
> +++ b/Documentation/fpga/fpga-mgr.txt
> @@ -0,0 +1,171 @@
> +FPGA Manager Core
> +
> +Alan Tull 2015
> +
> +Overview
> +========
> +
> +The FPGA manager core exports a set of functions for programming an FPGA with
> +image.  The API is manufacturer agnostic.  All manufacturer specifics are
... with an image ?
> +hidden away in a low level driver which registers a set of ops with the core.
> +The FPGA image data itself is very manufacturer specific, but for our purposes
> +it's just binary data.  The FPGA manager core won't parse it.
> +
> +
> +API Functions:
> +==============
> +
> +To program the FPGA from a file or from a buffer:
> +-------------------------------------------------
> +
> +       int fpga_mgr_buf_load(struct fpga_manager *mgr, u32 flags,
> +                             const char *buf, size_t count);
> +
> +Load the FPGA from an image which exists as a buffer in memory.
> +
> +       int fpga_mgr_firmware_load(struct fpga_manager *mgr, u32 flags,
> +                                  const char *image_name);
> +
> +Load the FPGA from an image which exists as a file.  The image file must be on
> +the firmware search path (see the firmware class documentation).
> +
> +For both these functions, flags == 0 for normal full reconfiguration or
> +FPGA_MGR_PARTIAL_RECONFIG for partial reconfiguration.  If successful, the FPGA
> +ends up in operating mode.  Return 0 on success or a negative error code.
> +
> +
> +To get/put a reference to a FPGA manager:
> +-----------------------------------------
> +
> +       struct fpga_manager *of_fpga_mgr_get(struct device_node *node);
> +
> +       void fpga_mgr_put(struct fpga_manager *mgr);
> +
> +Given a DT node, get an exclusive reference to a FPGA manager or release
> +the reference.
> +
> +
> +To register or unregister the low level FPGA-specific driver:
> +-------------------------------------------------------------
> +
> +       int fpga_mgr_register(struct device *dev, const char *name,
> +                             const struct fpga_manager_ops *mops,
> +                             void *priv);
> +
> +       void fpga_mgr_unregister(struct device *dev);
> +
> +Use of these two functions is described below in "How To Support a new FPGA
> +device."
> +
> +
> +How to write an image buffer to a supported FPGA
> +================================================
> +/* Include to get the API */
> +#include <linux/fpga/fpga-mgr.h>
> +
> +/* device node that specifies the FPGA manager to use */
> +struct device_node *mgr_node = ...
> +
> +/* FPGA image is in this buffer.  count is size of the buffer. */
> +char *buf = ...
> +int count = ...
> +
> +/* flags indicates whether to do full or partial reconfiguration */
> +int flags = 0;
> +
> +int ret;
> +
> +/* Get exclusive control of FPGA manager */
> +struct fpga_manager *mgr = of_fpga_mgr_get(mgr_node);
> +
> +/* Load the buffer to the FPGA */
> +ret = fpga_mgr_buf_load(mgr, flags, buf, count);
> +
> +/* Release the FPGA manager */
> +fpga_mgr_put(mgr);
> +
> +
> +How to write an image file to a supported FPGA
> +==============================================
> +/* Include to get the API */
> +#include <linux/fpga/fpga-mgr.h>
> +
> +/* device node that specifies the FPGA manager to use */
> +struct device_node *mgr_node = ...
> +
> +/* FPGA image is in this file which is on the firmware search path */
... in the firmware search path .. not sure if that's better though :)
> +const char *path = "fpga-image-9.rbf"
> +
> +/* flags indicates whether to do full or partial reconfiguration */
> +int flags = 0;
> +
> +int ret;
> +
> +/* Get exclusive control of FPGA manager */
> +struct fpga_manager *mgr = of_fpga_mgr_get(mgr_node);
> +
> +/* Get the firmware image (path) and load it to the FPGA */
> +ret = fpga_mgr_firmware_load(mgr, flags, path);
> +
> +/* Release the FPGA manager */
> +fpga_mgr_put(mgr);
> +
> +
> +How to support a new FPGA device
> +================================
> +To add another FPGA manager, write a driver that implements a set of ops.  The
> +probe function calls fpga_mgr_register(), such as:
> +
> +static const struct fpga_manager_ops socfpga_fpga_ops = {
> +       .write_init = socfpga_fpga_ops_configure_init,
> +       .write = socfpga_fpga_ops_configure_write,
> +       .write_complete = socfpga_fpga_ops_configure_complete,
> +       .state = socfpga_fpga_ops_state,
> +};
> +
> +static int socfpga_fpga_probe(struct platform_device *pdev)
> +{
> +       struct device *dev = &pdev->dev;
> +       struct socfpga_fpga_priv *priv;
> +       int ret;
> +
> +       priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +       if (!priv)
> +               return -ENOMEM;
> +
> +       /* ... do ioremaps, get interrupts, etc. and save
> +          them in priv... */
> +
> +       return fpga_mgr_register(dev, "Altera SOCFPGA FPGA Manager",
> +                                &socfpga_fpga_ops, priv);
> +}
> +
> +static int socfpga_fpga_remove(struct platform_device *pdev)
> +{
> +       fpga_mgr_unregister(&pdev->dev);
> +
> +       return 0;
> +}
> +
> +
> +The ops will implement whatever device specific register writes are needed to
> +do the programming sequence for this particular FPGA.  These ops return 0 for
> +success or negative error codes otherwise.
> +
> +The programming sequence is:
> + 1. .write_init
> + 2. .write (may be called once or multiple times)
> + 3. .write_complete
> +
> +The .write_init function will prepare the FPGA to receive the image data.
> +
> +The .write function writes a buffer to the FPGA. The buffer may be contain the
> +whole FPGA image or may be a smaller chunk of an FPGA image.  In the latter
> +case, this function is called multiple times for successive chunks.
> +
> +The .write_complete function is called after all the image has been written
> +to put the FPGA into operating mode.
> +
> +The ops include a .state function which will read the hardware FPGA manager and
> +return a code of type enum fpga_mgr_states.  It doesn't result in a change in
> +hardware state.
> --
> 1.7.9.5
>

Cheers,

Moritz
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