Re: [PATCH v9 3/3] fpga: Add support for Lattice iCE40 FPGAs

[Alan Tull]

On Fri, 9 Dec 2016, Moritz Fischer wrote:

> Joel,
> 
> A couple of minor nits below (none of them are real blockers), other
> than that looks good.
> 
> On Thu, Dec 8, 2016 at 9:35 PM, Joel Holdsworth
> <joel@xxxxxxxxxxxxxxxxxxx> wrote:
> > The Lattice iCE40 is a family of FPGAs with a minimalistic architecture
> > and very regular structure, designed for low-cost, high-volume consumer
> > and system applications.
> 
> <snip>
> 
> > This patch adds support to the FPGA manager for configuring the SRAM of
> > iCE40LM, iCE40LP, iCE40HX, iCE40 Ultra, iCE40 UltraLite and iCE40
> > UltraPlus devices, through slave SPI.
> 
> </snip>
> 
> I think just this paragraph would be enough.

With these changes,

Acked-by: Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx>

Thanks,
Alan


> >
> > The iCE40 family is notable because it is the first FPGA family to have
> > complete reverse engineered bit-stream documentation for the iCE40LP and
> > iCE40HX devices. Furthermore, there is now a Free Software Verilog
> > synthesis tool-chain: the "IceStorm" tool-chain.
> >
> > This project is the work of Clifford Wolf, who is the maintainer of
> > Yosys Verilog RTL synthesis framework, and Mathias Lasser, with notable
> > contributions from "Cotton Seed", the main author of "arachne-pnr"; a
> > place-and-route tool for iCE40 FPGAs.
> >
> > Having a Free Software synthesis tool-chain offers interesting
> > opportunities for embedded devices that are able reconfigure themselves
> > with open firmware that is generated on the device itself. For example
> > a mobile device might have an application processor with an iCE40 FPGA
> > attached, which implements slave devices, or through which the processor
> > communicates with other devices through the FPGA fabric.
> >
> > A kernel driver for the iCE40 is useful, because in some cases, the FPGA
> > may need to be configured before other devices can be accessed.
> >
> > An example of such a device is the icoBoard; a RaspberryPI HAT which
> > features an iCE40HX8K with a 1 or 8 MBit SRAM and ports for
> > Digilent-compatible PMOD modules. A PMOD module may contain a device
> > with which the kernel communicates, via the FPGA.
> >
> > Signed-off-by: Joel Holdsworth <joel@xxxxxxxxxxxxxxxxxxx>
> Modulo nits:
> 
> Reviewed-by: Moritz Fischer <moritz.fischer@xxxxxxxxx>
> 
> > ---
> >  drivers/fpga/Kconfig     |   6 ++
> >  drivers/fpga/Makefile    |   1 +
> >  drivers/fpga/ice40-spi.c | 213 +++++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 220 insertions(+)
> >  create mode 100644 drivers/fpga/ice40-spi.c
> >
> > diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
> > index ce861a2..967cda4 100644
> > --- a/drivers/fpga/Kconfig
> > +++ b/drivers/fpga/Kconfig
> > @@ -20,6 +20,12 @@ config FPGA_REGION
> >           FPGA Regions allow loading FPGA images under control of
> >           the Device Tree.
> >
> > +config FPGA_MGR_ICE40_SPI
> > +       tristate "Lattice iCE40 SPI"
> > +       depends on OF && SPI
> > +       help
> > +         FPGA manager driver support for Lattice iCE40 FPGAs over SPI.
> > +
> >  config FPGA_MGR_SOCFPGA
> >         tristate "Altera SOCFPGA FPGA Manager"
> >         depends on ARCH_SOCFPGA || COMPILE_TEST
> > diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
> > index 8df07bc..cc0d364 100644
> > --- a/drivers/fpga/Makefile
> > +++ b/drivers/fpga/Makefile
> > @@ -6,6 +6,7 @@
> >  obj-$(CONFIG_FPGA)                     += fpga-mgr.o
> >
> >  # FPGA Manager Drivers
> > +obj-$(CONFIG_FPGA_MGR_ICE40_SPI)       += ice40-spi.o
> >  obj-$(CONFIG_FPGA_MGR_SOCFPGA)         += socfpga.o
> >  obj-$(CONFIG_FPGA_MGR_SOCFPGA_A10)     += socfpga-a10.o
> >  obj-$(CONFIG_FPGA_MGR_ZYNQ_FPGA)       += zynq-fpga.o
> > diff --git a/drivers/fpga/ice40-spi.c b/drivers/fpga/ice40-spi.c
> > new file mode 100644
> > index 0000000..3c99859
> > --- /dev/null
> > +++ b/drivers/fpga/ice40-spi.c
> > @@ -0,0 +1,213 @@
> > +/*
> > + * FPGA Manager Driver for Lattice iCE40.
> > + *
> > + *  Copyright (c) 2016 Joel Holdsworth
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License as published by
> > + * the Free Software Foundation; version 2 of the License.
> > + *
> > + * This driver adds support to the FPGA manager for configuring the SRAM of
> > + * Lattice iCE40 FPGAs through slave SPI.
> > + */
> > +
> > +#include <linux/fpga/fpga-mgr.h>
> > +#include <linux/gpio/consumer.h>
> > +#include <linux/module.h>
> > +#include <linux/of_gpio.h>
> > +#include <linux/spi/spi.h>
> > +
> > +#define ICE40_SPI_FPGAMGR_RESET_DELAY 1 /* us (>200ns) */
> > +#define ICE40_SPI_FPGAMGR_HOUSEKEEPING_DELAY 1200 /* us */
> > +
> > +#define ICE40_SPI_FPGAMGR_NUM_ACTIVATION_BYTES DIV_ROUND_UP(49, 8)
> > +
> > +struct ice40_fpga_priv {
> > +       struct spi_device *dev;
> > +       struct gpio_desc *reset;
> > +       struct gpio_desc *cdone;
> > +};
> > +
> > +static enum fpga_mgr_states ice40_fpga_ops_state(struct fpga_manager *mgr)
> > +{
> > +       struct ice40_fpga_priv *priv = mgr->priv;
> > +
> > +       return gpiod_get_value(priv->cdone) ? FPGA_MGR_STATE_OPERATING :
> > +               FPGA_MGR_STATE_UNKNOWN;
> > +}
> > +
> > +static int ice40_fpga_ops_write_init(struct fpga_manager *mgr,
> > +                                    struct fpga_image_info *info,
> > +                                    const char *buf, size_t count)
> > +{
> > +       struct ice40_fpga_priv *priv = mgr->priv;
> > +       struct spi_device *dev = priv->dev;
> > +       struct spi_message message;
> > +       struct spi_transfer assert_cs_then_reset_delay = {
> > +               .cs_change   = 1,
> > +               .delay_usecs = ICE40_SPI_FPGAMGR_RESET_DELAY
> > +       };
> > +       struct spi_transfer housekeeping_delay_then_release_cs = {
> > +               .delay_usecs = ICE40_SPI_FPGAMGR_HOUSEKEEPING_DELAY
> > +       };
> > +       int ret;
> > +
> > +       if ((info->flags & FPGA_MGR_PARTIAL_RECONFIG)) {
> > +               dev_err(&dev->dev,
> > +                       "Partial reconfiguration is not supported\n");
> > +               return -ENOTSUPP;
> > +       }
> > +
> > +       /* Lock the bus, assert CRESET_B and SS_B and delay >200ns */
> > +       spi_bus_lock(dev->master);
> > +
> > +       gpiod_set_value(priv->reset, 1);
> > +
> > +       spi_message_init(&message);
> > +       spi_message_add_tail(&assert_cs_then_reset_delay, &message);
> > +       ret = spi_sync_locked(dev, &message);
> > +
> > +       /* Come out of reset */
> > +       gpiod_set_value(priv->reset, 0);
> > +
> > +       /* Abort if the chip-select failed */
> > +       if (ret)
> > +               goto fail;
> > +
> > +       /* Check CDONE is de-asserted i.e. the FPGA is reset */
> > +       if (gpiod_get_value(priv->cdone)) {
> > +               dev_err(&dev->dev, "Device reset failed, CDONE is asserted\n");
> > +               ret = -EIO;
> > +               goto fail;
> > +       }
> > +
> > +       /* Wait for the housekeeping to complete, and release SS_B */
> > +       spi_message_init(&message);
> > +       spi_message_add_tail(&housekeeping_delay_then_release_cs, &message);
> > +       ret = spi_sync_locked(dev, &message);
> > +
> > +fail:
> > +       spi_bus_unlock(dev->master);
> > +
> > +       return ret;
> > +}
> > +
> > +static int ice40_fpga_ops_write(struct fpga_manager *mgr,
> > +                               const char *buf, size_t count)
> > +{
> > +       struct ice40_fpga_priv *priv = mgr->priv;
> > +
> > +       return spi_write(priv->dev, buf, count);
> > +}
> > +
> > +static int ice40_fpga_ops_write_complete(struct fpga_manager *mgr,
> > +                                        struct fpga_image_info *info)
> > +{
> > +       struct ice40_fpga_priv *priv = mgr->priv;
> > +       struct spi_device *dev = priv->dev;
> > +       const u8 padding[ICE40_SPI_FPGAMGR_NUM_ACTIVATION_BYTES] = {0};
> > +
> > +       /* Check CDONE is asserted */
> > +       if (!gpiod_get_value(priv->cdone)) {
> > +               dev_err(&dev->dev,
> > +                       "CDONE was not asserted after firmware transfer\n");
> > +               return -EIO;
> > +       }
> > +
> > +       /* Send of zero-padding to activate the firmware */
> > +       return spi_write(dev, padding, sizeof(padding));
> > +}
> > +
> > +static const struct fpga_manager_ops ice40_fpga_ops = {
> > +       .state = ice40_fpga_ops_state,
> > +       .write_init = ice40_fpga_ops_write_init,
> > +       .write = ice40_fpga_ops_write,
> > +       .write_complete = ice40_fpga_ops_write_complete,
> > +};
> > +
> > +static int ice40_fpga_probe(struct spi_device *spi)
> > +{
> > +       struct device *dev = &spi->dev;
> > +       struct device_node *np = spi->dev.of_node;
> > +       struct ice40_fpga_priv *priv;
> > +       int ret;
> > +
> > +       if (!np) {
> > +               dev_err(dev, "No Device Tree entry\n");
> > +               return -EINVAL;
> > +       }
> > +
> > +       priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);
> > +       if (!priv)
> > +               return -ENOMEM;
> > +
> > +       priv->dev = spi;
> > +
> > +       /* Check board setup data. */
> > +       if (spi->max_speed_hz > 25000000) {
> > +               dev_err(dev, "Speed is too high\n");
> 
> Speed is too high, maximum speed is X. Maybe make it a ICE40_SPI_MAX_SPEED
> > +               return -EINVAL;
> > +       }
> > +
> > +       if (spi->max_speed_hz < 1000000) {
> > +               dev_err(dev, "Speed is too low\n");
> 
> Speed is too low, minimum speed is X. Maybe make it a ICE40_SPI_MIN_SPEED
> > +               return -EINVAL;
> > +       }
> > +
> > +       if (spi->mode & SPI_CPHA) {
> > +               dev_err(dev, "Bad mode\n");
> 
> 'Bad mode, SPI_CPHA not supported' mabye.
> > +               return -EINVAL;
> > +       }
> > +
> > +       /* Set up the GPIOs */
> > +       priv->cdone = devm_gpiod_get(dev, "cdone", GPIOD_IN);
> > +       if (IS_ERR(priv->cdone)) {
> > +               dev_err(dev, "Failed to get CDONE GPIO: %ld\n",
> > +                       PTR_ERR(priv->cdone));
> > +               return -EINVAL;
> > +       }
> > +
> > +       priv->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
> > +       if (IS_ERR(priv->reset)) {
> > +               dev_err(dev, "Failed to get CRESET_B GPIO: %ld\n",
> > +                       PTR_ERR(priv->reset));
> > +               return -EINVAL;
> > +       }
> > +
> > +       /* Register with the FPGA manager */
> > +       ret = fpga_mgr_register(dev, "Lattice iCE40 FPGA Manager",
> > +                               &ice40_fpga_ops, priv);
> > +       if (ret) {
> > +               dev_err(dev, "Unable to register FPGA manager");
> > +               return ret;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static int ice40_fpga_remove(struct spi_device *spi)
> > +{
> > +       fpga_mgr_unregister(&spi->dev);
> > +       return 0;
> > +}
> > +
> > +static const struct of_device_id ice40_fpga_of_match[] = {
> > +       { .compatible = "lattice,ice40-fpga-mgr", },
> > +       {},
> > +};
> > +MODULE_DEVICE_TABLE(of, ice40_fpga_of_match);
> > +
> > +static struct spi_driver ice40_fpga_driver = {
> > +       .probe = ice40_fpga_probe,
> > +       .remove = ice40_fpga_remove,
> > +       .driver = {
> > +               .name = "ice40spi",
> > +               .of_match_table = of_match_ptr(ice40_fpga_of_match),
> > +       },
> > +};
> > +
> > +module_spi_driver(ice40_fpga_driver);
> > +
> > +MODULE_AUTHOR("Joel Holdsworth <joel@xxxxxxxxxxxxxxxxxxx>");
> > +MODULE_DESCRIPTION("Lattice iCE40 FPGA Manager");
> > +MODULE_LICENSE("GPL v2");
> > --
> > 2.7.4
> >
> 
> Thanks,
> 
> Moritz
> 
> PS: can you also Cc linux-fpga mailing list in the future?
>