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kernel-hacking-2024-linux-s.../include/net/nfc/nci_core.h
Eric Lapuyade 2bed278517 NFC: NCI: Modify NCI SPI to implement CS/INT handshake per the spec 
The NFC Forum NCI specification defines both a hardware and software
protocol when using a SPI physical transport to connect an NFC NCI
Chipset. The hardware requirement is that, after having raised the chip
select line, the SPI driver must wait for an INT line from the NFC
chipset to raise before it sends the data. The chip select must be
raised first though, because this is the signal that the NFC chipset
will detect to wake up and then raise its INT line. If the INT line
doesn't raise in a timely fashion, the SPI driver should abort
operation.

When data is transferred from Device host (DH) to NFC Controller (NFCC),
the signaling sequence is the following:

Data Transfer from DH to NFCC
• 1-Master asserts SPI_CSN
• 2-Slave asserts SPI_INT
• 3-Master sends NCI-over-SPI protocol header and payload data
• 4-Slave deasserts SPI_INT
• 5-Master deasserts SPI_CSN

When data must be transferred from NFCC to DH, things are a little bit
different.

Data Transfer from NFCC to DH
• 1-Slave asserts SPI_INT -> NFC chipset irq handler called -> process
reading from SPI
• 2-Master asserts SPI_CSN
• 3-Master send 2-octet NCI-over-SPI protocol header
• 4-Slave sends 2-octet NCI-over-SPI protocol payload length
• 5-Slave sends NCI-over-SPI protocol payload
• 6-Master deasserts SPI_CSN

In this case, SPI driver should function normally as it does today. Note
that the INT line can and will be lowered anytime between beginning of
step 3 and end of step 5. A low INT is therefore valid after chip select
has been raised.

This would be easily implemented in a single driver. Unfortunately, we
don't write the SPI driver and I had to imagine some workaround trick to
get the SPI and NFC drivers to work in a synchronized fashion. The trick
is the following:

- send an empty spi message: this will raise the chip select line, and
send nothing. We expect the /CS line will stay arisen because we asked
for it in the spi_transfer cs_change field
- wait for a completion, that will be completed by the NFC driver IRQ
handler when it knows we are in the process of sending data (NFC spec
says that we use SPI in a half duplex mode, so we are either sending or
receiving).
- when completed, proceed with the normal data send.

This has been tested and verified to work very consistently on a Nexus
10 (spi-s3c64xx driver). It may not work the same with other spi
drivers.

The previously defined nci_spi_ops{} whose intended purpose were to
address this problem are not used anymore and therefore totally removed.

The nci_spi_send() takes a new optional write_handshake_completion
completion pointer. If non NULL, the nci spi layer will run the above
trick when sending data to the NFC Chip. If NULL, the data is sent
normally all at once and it is then the NFC driver responsibility to
know what it's doing.

Signed-off-by: Eric Lapuyade <eric.lapuyade@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
2013-09-25 14:59:56 +02:00

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/*
* The NFC Controller Interface is the communication protocol between an
* NFC Controller (NFCC) and a Device Host (DH).
*
* Copyright (C) 2011 Texas Instruments, Inc.
* Copyright (C) 2013 Intel Corporation. All rights reserved.
*
* Written by Ilan Elias <ilane@ti.com>
*
* Acknowledgements:
* This file is based on hci_core.h, which was written
* by Maxim Krasnyansky.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#ifndef __NCI_CORE_H
#define __NCI_CORE_H
#include <linux/interrupt.h>
#include <linux/skbuff.h>
#include <net/nfc/nfc.h>
#include <net/nfc/nci.h>
/* NCI device flags */
enum nci_flag {
NCI_INIT,
NCI_UP,
NCI_DATA_EXCHANGE,
NCI_DATA_EXCHANGE_TO,
};
/* NCI device states */
enum nci_state {
NCI_IDLE,
NCI_DISCOVERY,
NCI_W4_ALL_DISCOVERIES,
NCI_W4_HOST_SELECT,
NCI_POLL_ACTIVE,
};
/* NCI timeouts */
#define NCI_RESET_TIMEOUT 5000
#define NCI_INIT_TIMEOUT 5000
#define NCI_SET_CONFIG_TIMEOUT 5000
#define NCI_RF_DISC_TIMEOUT 5000
#define NCI_RF_DISC_SELECT_TIMEOUT 5000
#define NCI_RF_DEACTIVATE_TIMEOUT 30000
#define NCI_CMD_TIMEOUT 5000
#define NCI_DATA_TIMEOUT 700
struct nci_dev;
struct nci_ops {
int (*open)(struct nci_dev *ndev);
int (*close)(struct nci_dev *ndev);
int (*send)(struct nci_dev *ndev, struct sk_buff *skb);
};
#define NCI_MAX_SUPPORTED_RF_INTERFACES 4
#define NCI_MAX_DISCOVERED_TARGETS 10
/* NCI Core structures */
struct nci_dev {
struct nfc_dev *nfc_dev;
struct nci_ops *ops;
int tx_headroom;
int tx_tailroom;
atomic_t state;
unsigned long flags;
atomic_t cmd_cnt;
atomic_t credits_cnt;
struct timer_list cmd_timer;
struct timer_list data_timer;
struct workqueue_struct *cmd_wq;
struct work_struct cmd_work;
struct workqueue_struct *rx_wq;
struct work_struct rx_work;
struct workqueue_struct *tx_wq;
struct work_struct tx_work;
struct sk_buff_head cmd_q;
struct sk_buff_head rx_q;
struct sk_buff_head tx_q;
struct mutex req_lock;
struct completion req_completion;
__u32 req_status;
__u32 req_result;
void *driver_data;
__u32 poll_prots;
__u32 target_active_prot;
struct nfc_target targets[NCI_MAX_DISCOVERED_TARGETS];
int n_targets;
/* received during NCI_OP_CORE_RESET_RSP */
__u8 nci_ver;
/* received during NCI_OP_CORE_INIT_RSP */
__u32 nfcc_features;
__u8 num_supported_rf_interfaces;
__u8 supported_rf_interfaces
[NCI_MAX_SUPPORTED_RF_INTERFACES];
__u8 max_logical_connections;
__u16 max_routing_table_size;
__u8 max_ctrl_pkt_payload_len;
__u16 max_size_for_large_params;
__u8 manufact_id;
__u32 manufact_specific_info;
/* received during NCI_OP_RF_INTF_ACTIVATED_NTF */
__u8 max_data_pkt_payload_size;
__u8 initial_num_credits;
/* stored during nci_data_exchange */
data_exchange_cb_t data_exchange_cb;
void *data_exchange_cb_context;
struct sk_buff *rx_data_reassembly;
/* stored during intf_activated_ntf */
__u8 remote_gb[NFC_MAX_GT_LEN];
__u8 remote_gb_len;
};
/* ----- NCI Devices ----- */
struct nci_dev *nci_allocate_device(struct nci_ops *ops,
__u32 supported_protocols,
int tx_headroom,
int tx_tailroom);
void nci_free_device(struct nci_dev *ndev);
int nci_register_device(struct nci_dev *ndev);
void nci_unregister_device(struct nci_dev *ndev);
int nci_recv_frame(struct nci_dev *ndev, struct sk_buff *skb);
static inline struct sk_buff *nci_skb_alloc(struct nci_dev *ndev,
unsigned int len,
gfp_t how)
{
struct sk_buff *skb;
skb = alloc_skb(len + ndev->tx_headroom + ndev->tx_tailroom, how);
if (skb)
skb_reserve(skb, ndev->tx_headroom);
return skb;
}
static inline void nci_set_parent_dev(struct nci_dev *ndev, struct device *dev)
{
nfc_set_parent_dev(ndev->nfc_dev, dev);
}
static inline void nci_set_drvdata(struct nci_dev *ndev, void *data)
{
ndev->driver_data = data;
}
static inline void *nci_get_drvdata(struct nci_dev *ndev)
{
return ndev->driver_data;
}
void nci_rsp_packet(struct nci_dev *ndev, struct sk_buff *skb);
void nci_ntf_packet(struct nci_dev *ndev, struct sk_buff *skb);
void nci_rx_data_packet(struct nci_dev *ndev, struct sk_buff *skb);
int nci_send_cmd(struct nci_dev *ndev, __u16 opcode, __u8 plen, void *payload);
int nci_send_data(struct nci_dev *ndev, __u8 conn_id, struct sk_buff *skb);
void nci_data_exchange_complete(struct nci_dev *ndev, struct sk_buff *skb,
int err);
void nci_clear_target_list(struct nci_dev *ndev);
/* ----- NCI requests ----- */
#define NCI_REQ_DONE 0
#define NCI_REQ_PEND 1
#define NCI_REQ_CANCELED 2
void nci_req_complete(struct nci_dev *ndev, int result);
/* ----- NCI status code ----- */
int nci_to_errno(__u8 code);
/* ----- NCI over SPI acknowledge modes ----- */
#define NCI_SPI_CRC_DISABLED 0x00
#define NCI_SPI_CRC_ENABLED 0x01
/* ----- NCI SPI structures ----- */
struct nci_spi {
struct nci_dev *ndev;
struct spi_device *spi;
unsigned int xfer_udelay; /* microseconds delay between
transactions */
u8 acknowledge_mode;
struct completion req_completion;
u8 req_result;
};
/* ----- NCI SPI ----- */
struct nci_spi *nci_spi_allocate_spi(struct spi_device *spi,
u8 acknowledge_mode, unsigned int delay,
struct nci_dev *ndev);
int nci_spi_send(struct nci_spi *nspi,
struct completion *write_handshake_completion,
struct sk_buff *skb);
struct sk_buff *nci_spi_read(struct nci_spi *nspi);
#endif /* __NCI_CORE_H */
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