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[spi_device] Remove generic mode
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Remove generic mode from spi_device.

Generic mode has a very different timing model than the relatively high
throughput, high latency flash and tpm modes. Generic mode requires data
to be available on the MISO pin *before* the first SCK edge, whereas
flash and tpm modes have a significant command phase that comes first.
In addition, generic mode requires support for a number of different
idle clock polarities and sampling phases, whereas flash and TPM modes
have one clearly defined set.

The complexity for supporting both timing models for one IP led to a
compromised performance for flash and TPM. Remove generic mode here to
permit optimizations that target the latter modes.

Signed-off-by: Alexander Williams <[email protected]>
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@a-will
a-will committed Jan 23, 2024
1 parent 7203583 commit 726cd46
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299 changes: 17 additions & 282 deletions hw/ip/spi_device/data/spi_device.hjson
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,7 @@
human_name: "SPI Device",
one_line_desc: "Serial peripheral interface supporting different device modes, suitable for bulk-load of data into and out of the chip",
one_paragraph_desc: '''
SPI Device is a configurable, versatile hardware block that implements a generic SPI device mode, plus three additional modes (SPI Flash emulation mode, SPI passthrough mode, and TPM over SPI mode) to support a variety of different applications.
For example, generic mode can be used in a raw data transfer protocol termed "Firmware Operation Mode", which is intended to be used to bulk-load data into and out of the chip.
SPI Device is a configurable, versatile hardware block that implements three modes (SPI Flash emulation mode, SPI passthrough mode, and TPM over SPI mode) to support a variety of different applications.
TPM over SPI operates in compliance with TPM PC Client Platform, unloading this protocol from a software solution.
SPI Flash emulation mode supports many JEDEC standard commands such as Read Status, Read JEDEC ID, Read SFDP, EN4B/EX4B, and multiple other read commands, allowing OpenTitan to provide, for example, verified boot firmware to other external devices.
'''
Expand Down Expand Up @@ -35,6 +34,14 @@
commit_id: "",
notes: ""
}
{ version: "2.0.0",
life_stage: "L1",
design_stage: "D1",
verification_stage: "V1",
dif_stage: "S1",
commit_id: "",
notes: ""
}
]
clocking: [
{clock: "clk_i", reset: "rst_ni", primary: true},
Expand All @@ -59,27 +66,6 @@
}
]
interrupt_list: [
{ name: "generic_rx_full"
desc: "RX SRAM FIFO Full"
}
{ name: "generic_rx_watermark"
desc: "RX SRAM FIFO is above the level"
}
{ name: "generic_tx_watermark"
desc: "TX SRAM FIFO is under the level"
}
{ name: "generic_rx_error"
desc: "SDI in FwMode has error"
type: "event"
}
{ name: "generic_rx_overflow"
desc: "RX Async FIFO overflow"
type: "event"
}
{ name: "generic_tx_underflow"
desc: "TX Async FIFO underflow"
type: "event"
}
{ name: "upload_cmdfifo_not_empty"
desc: "Upload Command FIFO is not empty"
}
Expand Down Expand Up @@ -191,12 +177,6 @@
}
],
features: [
{
name: "SPI_DEVICE.MODE.GENERIC",
desc: '''Single-lane SPI device interface implementing a raw data transfer protocol for bulk-data loading.
AKA. Firmware Operation Mode
'''
}
{
name: "SPI_DEVICE.MODE.FLASH_EMULATION",
desc: '''Emulates the behaviour of a Serial Flash device when connected to an upstream SPI Host.
Expand Down Expand Up @@ -246,35 +226,6 @@
desc: '''CSR.STATUS fields show the current status of the two CSB signals (.csb/.tpm_csb).
'''
}
{
name: "SPI_DEVICE.MODE.GENERIC.ASYNC_FIFOS",
desc: '''A pair of asynchronous FIFOs (RXFIFO/TXFIFO) interface with the bus in Generic mode.

- The bus-facing side of the FIFOs is driven by the bus-CLK.
- The internal-facing side of the FIFOs is driven by the core-CLK.
- Generic-mode logic interfaces the internal-facing sides of the FIFOs with the DPSRAM.
- Generic-mode uses the entire DPSRAM space exclusively (See feature SPI_DEVICE.MODE.GENERIC.DPSRAM_TXF_RXF).
- Writing to "CSR.CONTROL.rst_txfifo" soft-resets the contents of the TXFIFO.
- Received data is normally written from the RXFIFO output to the DPSRAM receive buffer on 32b word boundaries.
- "CSR.CFG.timer_v" provides configurable control of the delay between the end of unaligned receive data and
the construction of an (abnormal) sub-word write to the DPSRAM receive buffer.
- "CSR.ASYNC_FIFO_LEVEL.txlvl" and "CSR.ASYNC_FIFO_LEVEL.rxlvl" contain the current levels of each FIFO.
'''
}
{
name: "SPI_DEVICE.MODE.GENERIC.DPSRAM_TXF_RXF",
desc: '''A dual-port SRAM, notionally split into transmit (TXF) and receive (RXF) circular buffers, holds data in Generic Mode.

- TXF and RXF sections are defined by CSR.RXF_ADDR and CSR.TXF_ADDR, each of which contains a base and limit value.
- The boundary between TXF and RXF sections is configurable at runtime by writing to CSR.RXF_ADDR and CSR.TXF_ADDR.
- The current contents of TXF and RXF is defined by CSR.TXF_PTR and CSR.RXF_PTR, each of which contain a rptr and wptr.
- HW interfaces the buffers with the bus through two async-fifos (See feature SPI_DEVICE.MODE.GENERIC.ASYNC_FIFOS).
- CSR.TXF_PTR.rptr and CSR.RXF_PTR.wptr are controlled by HW in response to bus operations that consume or provide data.
- SW updates the rptr/wptr values to indicate it has written-to or read-from each buffer.
- CSR.STATUS contains empty and full flags for each buffer (.txf_empty/.txf_full/.rxf_empty/.rxf_full)
-
'''
}
{
name: "SPI_DEVICE.MODE.FLASH_EMULATION.COMMANDS",
desc: '''Device should respond to all specified standard SPI Flash Commands.
Expand Down Expand Up @@ -404,30 +355,17 @@
swaccess: "rw",
hwaccess: "hro",
fields: [
{ bits: "0",
name: "ABORT",
desc: '''Abort pending TX data in Generic mode.

If TX_FIFO (Asynchronous) is full, the TXF waits indefinitely to
push the next byte into the asynchronous FIFO. SW may reset the
Async FIFO along with aborting the current task. SW should update
the write pointer of the TXF in order not to push the byte to
Asynchronous FIFO again by TXF logic.
'''
resval: "0"
},
{ bits: "5:4",
name: "MODE",
desc: "SPI Device operation mode. Currently only FwMode is supported.",
desc: "SPI Device flash operation mode.",
resval: "1"
enum: [
{ value: "0",
name: "fwmode",
desc: '''
FW operation mode.
name: "disabled",
desc: '''SPI Flash operations disabled.

HW just dumps incoming data to SRAM and reads from SRAM and
sends to SDO. This mode doesn't support Dual or Quad mode
SPI device flash operations are disabled, and all transactions are ignored.
Note that SPI TPM operations are controlled by !!TPM_CFG
'''
},
{ value: "1"
Expand Down Expand Up @@ -457,51 +395,6 @@
// passed between spi_dev/host due to passthrough
"excl:CsrNonInitTests:CsrExclWrite"]
},
{ bits: "16",
name: "rst_txfifo",
desc: '''
Reset Async TX_FIFO.

This only resets asynchronous fifo. If firmware wants to reset SRAM
FIFO, it should write 0 into read/write pointers.

_Note_: This value should be controlled only when SPI interface is
in Idle state as this reset signal doesn't have reset synchronizer.
'''
resval: "0",
},
{ bits: "17",
name: "rst_rxfifo",
desc: '''
Reset Async RX_FIFO.

This only resets asynchronous fifo. If firmware wants to reset SRAM
FIFO, it should write 0 into read pointer and write pointer.

_Note_: This value should be controlled only when SPI interface is
in Idle state as this reset signal doesn't have reset synchronizer.
'''
resval: "0",
},
{ bits: "31"
name: "sram_clk_en",
desc: '''SRAM Clock Enable.

This controls the clock gating cell lying on DP SRAM clock. As the
nature of absent of SPI_CLK in idle state, the clock mux for SRAM
B port cannot be glitch-free MUX. So, it is up to SW to change the
clock safely.

Programming sequence:

1. Check if SPI line is idle
2. Clear sram_clk_en to 0.
3. Change mode to FwMode for peri clk, FlashMode or PassThrough
for SPI_CLK.
4. Set sram_clk_en to 1.
'''
resval: "1"
}
]
},
{ name: "CFG",
Expand Down Expand Up @@ -529,16 +422,6 @@
desc: "RX bit order on SDI. Module stores bitstream from MSB to LSB if value is 0.",
resval: "0",
},
{ bits: "15:8",
name: "timer_v",
desc: '''
number of clocks for RXF to wait.

To reduce traffic to SRAM, RXF control module waits given clock cycle
if it doesn't fill SRAM data width even if Async RX FIFO is empty.
'''
resval: "0x7F",
},
{ bits: "16"
name: "addr_4b_en"
swaccess: "rw"
Expand Down Expand Up @@ -568,75 +451,12 @@
} // f: mailbox_en
]
},
{ name: "FIFO_LEVEL",
desc: "RX/ TX FIFO levels.",
swaccess: "rw",
hwaccess: "hro",
fields: [
{ bits: "15:0",
name: "rxlvl",
resval: "0x80",
desc: '''
RX FIFO level.

If RX SRAM FIFO level exceeds this value, it triggers interrupt.
'''
},
{ bits: "31:16",
name: "txlvl",
resval: "0x0",
desc: '''
TX FIFO level.

If TX SRAM FIFO level drops below this value, it triggers interrupt.
'''
},
],
},
{ name: "ASYNC_FIFO_LEVEL",
desc: "RX/ TX Async FIFO levels between main clk and spi clock",
swaccess: "ro",
hwaccess: "hwo",
hwext: "true",
fields: [
{ bits: "23:16",
name: "txlvl",
desc: '''
TX Async FIFO level.

This value shows the number of available entry in TX Async FIFO.
If the software writes message into SRAM FIFO and update FIFO write pointer
but no clock from the host is given, the data stuck at this async fifo waiting
host toggles SCK. This value represents the number of bytes.
'''
},
{ bits: "7:0",
name: "rxlvl",
desc: '''
RX Async FIFO level.

This value shows the number of available entry in RX Async FIFO.
'''
}
]
},
{ name: "STATUS",
desc: "SPI Device status register",
swaccess: "ro",
hwaccess: "hwo",
hwext: "true",
fields: [
{ bits: "0", name: "rxf_full", desc: "RX FIFO full" },
{ bits: "1", name: "rxf_empty", desc: "RX FIFO empty", resval: "1"},
{ bits: "2", name: "txf_full", desc: "TX FIFO full"},
{ bits: "3", name: "txf_empty", desc: "TX FIFO empty", resval: "1"},
{ bits: "4", name: "abort_done",
desc: '''Abort process is completed.

Current version does not implement abort_done logic. It is tied to
1 always.
'''
resval: "1" },
{ bits: "5", name: "csb", desc: "Direct input of CSb signal", resval: "1" },
{ bits: "6"
name: "tpm_csb"
Expand All @@ -650,90 +470,6 @@
}
]
},
{ name: "RXF_PTR",
desc: "Receiver FIFO (SRAM) pointers",
swaccess: "rw",
hwaccess: "hrw",
fields: [
{ bits: "15:0",
name: "RPTR",
desc: "Read pointer. bit x is for phase bit. check circular fifo description",
swaccess: "rw",
hwaccess: "hro",
resval: "0",
tags: [// Updating rptr will cause unexpected interrupts. These interrupts may take a
// while to generate and cip_base_vseq::clear_all_interrupts may not be able to
// clear them in time. Leftover interrupts will cause sim error
"excl:CsrNonInitTests:CsrExclWrite"]
},
{ bits: "31:16",
name: "WPTR",
desc: "Write pointer. Bit x is phase bit.",
swaccess: "ro",
hwaccess: "hwo",
resval: "0",
}
]
},
{ name: "TXF_PTR",
desc: "Transmitter FIFO (SRAM) pointers",
swaccess: "rw",
hwaccess: "hrw",
fields: [
{ bits: "15:0",
name: "RPTR",
desc: "Read pointer. bit x is for phase bit. check circular fifo description",
swaccess: "ro",
hwaccess: "hwo",
resval: "0",
},
{ bits: "31:16",
name: "WPTR",
desc: "Write pointer. Bit x is phase bit.",
swaccess: "rw",
hwaccess: "hro",
resval: "0",
tags: [// Updating rptr will cause unexpected interrupts. These interrupts may take a
// while to generate and cip_base_vseq::clear_all_interrupts may not be able to
// clear them in time. Leftover interrupts will cause sim error
"excl:CsrNonInitTests:CsrExclWrite"]
}
]
},
{ name: "RXF_ADDR",
desc: "Receiver FIFO (SRAM) Addresses",
swaccess: "rw",
hwaccess: "hro",
fields: [
{ bits: "15:0",
name: "base",
desc: "Base offset in bytes in the SRAM. Lower 2 bits are ignored.",
resval: "0",
},
{ bits: "31:16",
name: "limit",
desc: "Limit offset in bytes in the SRAM. Lower 2 bits are ignored.",
resval: "0x1FC",
}
],
},
{ name: "TXF_ADDR",
desc: "Transmitter FIFO (SRAM) Addresses",
swaccess: "rw",
hwaccess: "hro",
fields: [
{ bits: "15:0",
name: "base",
desc: "Base offset in bytes in the SRAM. Lower 2 bits are ignored.",
resval: "0x200",
},
{ bits: "31:16",
name: "limit",
desc: "Limit offset in bytes in the SRAM. Lower 2 bits are ignored.",
resval: "0x3FC",
}
],
},
//=========================================================================
// Flash & Passthrough CSRs
{ name: "INTERCEPT_EN"
Expand Down Expand Up @@ -1590,10 +1326,9 @@
desc: '''
SPI internal buffer.

In Generic mode, this buffer is used for RX/TX buffer. In Flash &
Passthrough mode, lower 2kB is for Read content emulating eFlash.
next 1kB is for Mailbox read/write buffer. The rest is 256B SFDP
buffer, 32B of CmdFIFO, 32B of AddrFIFO, and 256B of payload FIFO.
The lower 2kB is for Read content emulating eFlash. The next 1 kB is
for Mailbox read/write buffer. The rest is 256B SFDP buffer, 32B of
CmdFIFO, 32B of AddrFIFO, and 256B of payload FIFO.
'''
},
},
Expand Down
1 change: 0 additions & 1 deletion hw/ip/spi_device/doc/generic-blockdiagram.svg
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