diff options
Diffstat (limited to 'drivers/fsi/fsi-core.c')
-rw-r--r-- | drivers/fsi/fsi-core.c | 841 |
1 files changed, 841 insertions, 0 deletions
diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c index 3d55bd547178..a485864cb512 100644 --- a/drivers/fsi/fsi-core.c +++ b/drivers/fsi/fsi-core.c @@ -13,9 +13,830 @@ * GNU General Public License for more details. */ +#include <linux/crc4.h> #include <linux/device.h> #include <linux/fsi.h> +#include <linux/idr.h> #include <linux/module.h> +#include <linux/slab.h> +#include <linux/bitops.h> + +#include "fsi-master.h" + +#define CREATE_TRACE_POINTS +#include <trace/events/fsi.h> + +#define FSI_SLAVE_CONF_NEXT_MASK GENMASK(31, 31) +#define FSI_SLAVE_CONF_SLOTS_MASK GENMASK(23, 16) +#define FSI_SLAVE_CONF_SLOTS_SHIFT 16 +#define FSI_SLAVE_CONF_VERSION_MASK GENMASK(15, 12) +#define FSI_SLAVE_CONF_VERSION_SHIFT 12 +#define FSI_SLAVE_CONF_TYPE_MASK GENMASK(11, 4) +#define FSI_SLAVE_CONF_TYPE_SHIFT 4 +#define FSI_SLAVE_CONF_CRC_SHIFT 4 +#define FSI_SLAVE_CONF_CRC_MASK GENMASK(3, 0) +#define FSI_SLAVE_CONF_DATA_BITS 28 + +#define FSI_PEEK_BASE 0x410 + +static const int engine_page_size = 0x400; + +#define FSI_SLAVE_BASE 0x800 + +/* + * FSI slave engine control register offsets + */ +#define FSI_SMODE 0x0 /* R/W: Mode register */ +#define FSI_SISC 0x8 /* R/W: Interrupt condition */ +#define FSI_SSTAT 0x14 /* R : Slave status */ +#define FSI_LLMODE 0x100 /* R/W: Link layer mode register */ + +/* + * SMODE fields + */ +#define FSI_SMODE_WSC 0x80000000 /* Warm start done */ +#define FSI_SMODE_ECRC 0x20000000 /* Hw CRC check */ +#define FSI_SMODE_SID_SHIFT 24 /* ID shift */ +#define FSI_SMODE_SID_MASK 3 /* ID Mask */ +#define FSI_SMODE_ED_SHIFT 20 /* Echo delay shift */ +#define FSI_SMODE_ED_MASK 0xf /* Echo delay mask */ +#define FSI_SMODE_SD_SHIFT 16 /* Send delay shift */ +#define FSI_SMODE_SD_MASK 0xf /* Send delay mask */ +#define FSI_SMODE_LBCRR_SHIFT 8 /* Clk ratio shift */ +#define FSI_SMODE_LBCRR_MASK 0xf /* Clk ratio mask */ + +/* + * LLMODE fields + */ +#define FSI_LLMODE_ASYNC 0x1 + +#define FSI_SLAVE_SIZE_23b 0x800000 + +static DEFINE_IDA(master_ida); + +struct fsi_slave { + struct device dev; + struct fsi_master *master; + int id; + int link; + uint32_t size; /* size of slave address space */ +}; + +#define to_fsi_master(d) container_of(d, struct fsi_master, dev) +#define to_fsi_slave(d) container_of(d, struct fsi_slave, dev) + +static const int slave_retries = 2; +static int discard_errors; + +static int fsi_master_read(struct fsi_master *master, int link, + uint8_t slave_id, uint32_t addr, void *val, size_t size); +static int fsi_master_write(struct fsi_master *master, int link, + uint8_t slave_id, uint32_t addr, const void *val, size_t size); +static int fsi_master_break(struct fsi_master *master, int link); + +/* + * fsi_device_read() / fsi_device_write() / fsi_device_peek() + * + * FSI endpoint-device support + * + * Read / write / peek accessors for a client + * + * Parameters: + * dev: Structure passed to FSI client device drivers on probe(). + * addr: FSI address of given device. Client should pass in its base address + * plus desired offset to access its register space. + * val: For read/peek this is the value read at the specified address. For + * write this is value to write to the specified address. + * The data in val must be FSI bus endian (big endian). + * size: Size in bytes of the operation. Sizes supported are 1, 2 and 4 bytes. + * Addresses must be aligned on size boundaries or an error will result. + */ +int fsi_device_read(struct fsi_device *dev, uint32_t addr, void *val, + size_t size) +{ + if (addr > dev->size || size > dev->size || addr > dev->size - size) + return -EINVAL; + + return fsi_slave_read(dev->slave, dev->addr + addr, val, size); +} +EXPORT_SYMBOL_GPL(fsi_device_read); + +int fsi_device_write(struct fsi_device *dev, uint32_t addr, const void *val, + size_t size) +{ + if (addr > dev->size || size > dev->size || addr > dev->size - size) + return -EINVAL; + + return fsi_slave_write(dev->slave, dev->addr + addr, val, size); +} +EXPORT_SYMBOL_GPL(fsi_device_write); + +int fsi_device_peek(struct fsi_device *dev, void *val) +{ + uint32_t addr = FSI_PEEK_BASE + ((dev->unit - 2) * sizeof(uint32_t)); + + return fsi_slave_read(dev->slave, addr, val, sizeof(uint32_t)); +} + +static void fsi_device_release(struct device *_device) +{ + struct fsi_device *device = to_fsi_dev(_device); + + kfree(device); +} + +static struct fsi_device *fsi_create_device(struct fsi_slave *slave) +{ + struct fsi_device *dev; + + dev = kzalloc(sizeof(*dev), GFP_KERNEL); + if (!dev) + return NULL; + + dev->dev.parent = &slave->dev; + dev->dev.bus = &fsi_bus_type; + dev->dev.release = fsi_device_release; + + return dev; +} + +/* FSI slave support */ +static int fsi_slave_calc_addr(struct fsi_slave *slave, uint32_t *addrp, + uint8_t *idp) +{ + uint32_t addr = *addrp; + uint8_t id = *idp; + + if (addr > slave->size) + return -EINVAL; + + /* For 23 bit addressing, we encode the extra two bits in the slave + * id (and the slave's actual ID needs to be 0). + */ + if (addr > 0x1fffff) { + if (slave->id != 0) + return -EINVAL; + id = (addr >> 21) & 0x3; + addr &= 0x1fffff; + } + + *addrp = addr; + *idp = id; + return 0; +} + +int fsi_slave_report_and_clear_errors(struct fsi_slave *slave) +{ + struct fsi_master *master = slave->master; + uint32_t irq, stat; + int rc, link; + uint8_t id; + + link = slave->link; + id = slave->id; + + rc = fsi_master_read(master, link, id, FSI_SLAVE_BASE + FSI_SISC, + &irq, sizeof(irq)); + if (rc) + return rc; + + rc = fsi_master_read(master, link, id, FSI_SLAVE_BASE + FSI_SSTAT, + &stat, sizeof(stat)); + if (rc) + return rc; + + dev_info(&slave->dev, "status: 0x%08x, sisc: 0x%08x\n", + be32_to_cpu(stat), be32_to_cpu(irq)); + + /* clear interrupts */ + return fsi_master_write(master, link, id, FSI_SLAVE_BASE + FSI_SISC, + &irq, sizeof(irq)); +} + +static int fsi_slave_set_smode(struct fsi_master *master, int link, int id); + +int fsi_slave_handle_error(struct fsi_slave *slave, bool write, uint32_t addr, + size_t size) +{ + struct fsi_master *master = slave->master; + int rc, link; + uint32_t reg; + uint8_t id; + + if (discard_errors) + return -1; + + link = slave->link; + id = slave->id; + + dev_dbg(&slave->dev, "handling error on %s to 0x%08x[%zd]", + write ? "write" : "read", addr, size); + + /* try a simple clear of error conditions, which may fail if we've lost + * communication with the slave + */ + rc = fsi_slave_report_and_clear_errors(slave); + if (!rc) + return 0; + + /* send a TERM and retry */ + if (master->term) { + rc = master->term(master, link, id); + if (!rc) { + rc = fsi_master_read(master, link, id, 0, + ®, sizeof(reg)); + if (!rc) + rc = fsi_slave_report_and_clear_errors(slave); + if (!rc) + return 0; + } + } + + /* getting serious, reset the slave via BREAK */ + rc = fsi_master_break(master, link); + if (rc) + return rc; + + rc = fsi_slave_set_smode(master, link, id); + if (rc) + return rc; + + return fsi_slave_report_and_clear_errors(slave); +} + +int fsi_slave_read(struct fsi_slave *slave, uint32_t addr, + void *val, size_t size) +{ + uint8_t id = slave->id; + int rc, err_rc, i; + + rc = fsi_slave_calc_addr(slave, &addr, &id); + if (rc) + return rc; + + for (i = 0; i < slave_retries; i++) { + rc = fsi_master_read(slave->master, slave->link, + id, addr, val, size); + if (!rc) + break; + + err_rc = fsi_slave_handle_error(slave, false, addr, size); + if (err_rc) + break; + } + + return rc; +} +EXPORT_SYMBOL_GPL(fsi_slave_read); + +int fsi_slave_write(struct fsi_slave *slave, uint32_t addr, + const void *val, size_t size) +{ + uint8_t id = slave->id; + int rc, err_rc, i; + + rc = fsi_slave_calc_addr(slave, &addr, &id); + if (rc) + return rc; + + for (i = 0; i < slave_retries; i++) { + rc = fsi_master_write(slave->master, slave->link, + id, addr, val, size); + if (!rc) + break; + + err_rc = fsi_slave_handle_error(slave, true, addr, size); + if (err_rc) + break; + } + + return rc; +} +EXPORT_SYMBOL_GPL(fsi_slave_write); + +extern int fsi_slave_claim_range(struct fsi_slave *slave, + uint32_t addr, uint32_t size) +{ + if (addr + size < addr) + return -EINVAL; + + if (addr + size > slave->size) + return -EINVAL; + + /* todo: check for overlapping claims */ + return 0; +} +EXPORT_SYMBOL_GPL(fsi_slave_claim_range); + +extern void fsi_slave_release_range(struct fsi_slave *slave, + uint32_t addr, uint32_t size) +{ +} +EXPORT_SYMBOL_GPL(fsi_slave_release_range); + +static int fsi_slave_scan(struct fsi_slave *slave) +{ + uint32_t engine_addr; + uint32_t conf; + int rc, i; + + /* + * scan engines + * + * We keep the peek mode and slave engines for the core; so start + * at the third slot in the configuration table. We also need to + * skip the chip ID entry at the start of the address space. + */ + engine_addr = engine_page_size * 3; + for (i = 2; i < engine_page_size / sizeof(uint32_t); i++) { + uint8_t slots, version, type, crc; + struct fsi_device *dev; + + rc = fsi_slave_read(slave, (i + 1) * sizeof(conf), + &conf, sizeof(conf)); + if (rc) { + dev_warn(&slave->dev, + "error reading slave registers\n"); + return -1; + } + conf = be32_to_cpu(conf); + + crc = crc4(0, conf, 32); + if (crc) { + dev_warn(&slave->dev, + "crc error in slave register at 0x%04x\n", + i); + return -1; + } + + slots = (conf & FSI_SLAVE_CONF_SLOTS_MASK) + >> FSI_SLAVE_CONF_SLOTS_SHIFT; + version = (conf & FSI_SLAVE_CONF_VERSION_MASK) + >> FSI_SLAVE_CONF_VERSION_SHIFT; + type = (conf & FSI_SLAVE_CONF_TYPE_MASK) + >> FSI_SLAVE_CONF_TYPE_SHIFT; + + /* + * Unused address areas are marked by a zero type value; this + * skips the defined address areas + */ + if (type != 0 && slots != 0) { + + /* create device */ + dev = fsi_create_device(slave); + if (!dev) + return -ENOMEM; + + dev->slave = slave; + dev->engine_type = type; + dev->version = version; + dev->unit = i; + dev->addr = engine_addr; + dev->size = slots * engine_page_size; + + dev_dbg(&slave->dev, + "engine[%i]: type %x, version %x, addr %x size %x\n", + dev->unit, dev->engine_type, version, + dev->addr, dev->size); + + dev_set_name(&dev->dev, "%02x:%02x:%02x:%02x", + slave->master->idx, slave->link, + slave->id, i - 2); + + rc = device_register(&dev->dev); + if (rc) { + dev_warn(&slave->dev, "add failed: %d\n", rc); + put_device(&dev->dev); + } + } + + engine_addr += slots * engine_page_size; + + if (!(conf & FSI_SLAVE_CONF_NEXT_MASK)) + break; + } + + return 0; +} + +static ssize_t fsi_slave_sysfs_raw_read(struct file *file, + struct kobject *kobj, struct bin_attribute *attr, char *buf, + loff_t off, size_t count) +{ + struct fsi_slave *slave = to_fsi_slave(kobj_to_dev(kobj)); + size_t total_len, read_len; + int rc; + + if (off < 0) + return -EINVAL; + + if (off > 0xffffffff || count > 0xffffffff || off + count > 0xffffffff) + return -EINVAL; + + for (total_len = 0; total_len < count; total_len += read_len) { + read_len = min_t(size_t, count, 4); + read_len -= off & 0x3; + + rc = fsi_slave_read(slave, off, buf + total_len, read_len); + if (rc) + return rc; + + off += read_len; + } + + return count; +} + +static ssize_t fsi_slave_sysfs_raw_write(struct file *file, + struct kobject *kobj, struct bin_attribute *attr, + char *buf, loff_t off, size_t count) +{ + struct fsi_slave *slave = to_fsi_slave(kobj_to_dev(kobj)); + size_t total_len, write_len; + int rc; + + if (off < 0) + return -EINVAL; + + if (off > 0xffffffff || count > 0xffffffff || off + count > 0xffffffff) + return -EINVAL; + + for (total_len = 0; total_len < count; total_len += write_len) { + write_len = min_t(size_t, count, 4); + write_len -= off & 0x3; + + rc = fsi_slave_write(slave, off, buf + total_len, write_len); + if (rc) + return rc; + + off += write_len; + } + + return count; +} + +static struct bin_attribute fsi_slave_raw_attr = { + .attr = { + .name = "raw", + .mode = 0600, + }, + .size = 0, + .read = fsi_slave_sysfs_raw_read, + .write = fsi_slave_sysfs_raw_write, +}; + +static ssize_t fsi_slave_sysfs_term_write(struct file *file, + struct kobject *kobj, struct bin_attribute *attr, + char *buf, loff_t off, size_t count) +{ + struct fsi_slave *slave = to_fsi_slave(kobj_to_dev(kobj)); + struct fsi_master *master = slave->master; + + if (!master->term) + return -ENODEV; + + master->term(master, slave->link, slave->id); + return count; +} + +static struct bin_attribute fsi_slave_term_attr = { + .attr = { + .name = "term", + .mode = 0200, + }, + .size = 0, + .write = fsi_slave_sysfs_term_write, +}; + +/* Encode slave local bus echo delay */ +static inline uint32_t fsi_smode_echodly(int x) +{ + return (x & FSI_SMODE_ED_MASK) << FSI_SMODE_ED_SHIFT; +} + +/* Encode slave local bus send delay */ +static inline uint32_t fsi_smode_senddly(int x) +{ + return (x & FSI_SMODE_SD_MASK) << FSI_SMODE_SD_SHIFT; +} + +/* Encode slave local bus clock rate ratio */ +static inline uint32_t fsi_smode_lbcrr(int x) +{ + return (x & FSI_SMODE_LBCRR_MASK) << FSI_SMODE_LBCRR_SHIFT; +} + +/* Encode slave ID */ +static inline uint32_t fsi_smode_sid(int x) +{ + return (x & FSI_SMODE_SID_MASK) << FSI_SMODE_SID_SHIFT; +} + +static const uint32_t fsi_slave_smode(int id) +{ + return FSI_SMODE_WSC | FSI_SMODE_ECRC + | fsi_smode_sid(id) + | fsi_smode_echodly(0xf) | fsi_smode_senddly(0xf) + | fsi_smode_lbcrr(0x8); +} + +static int fsi_slave_set_smode(struct fsi_master *master, int link, int id) +{ + uint32_t smode; + + /* set our smode register with the slave ID field to 0; this enables + * extended slave addressing + */ + smode = fsi_slave_smode(id); + smode = cpu_to_be32(smode); + + return fsi_master_write(master, link, id, FSI_SLAVE_BASE + FSI_SMODE, + &smode, sizeof(smode)); +} + +static void fsi_slave_release(struct device *dev) +{ + struct fsi_slave *slave = to_fsi_slave(dev); + + kfree(slave); +} + +static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id) +{ + uint32_t chip_id, llmode; + struct fsi_slave *slave; + uint8_t crc; + int rc; + + /* Currently, we only support single slaves on a link, and use the + * full 23-bit address range + */ + if (id != 0) + return -EINVAL; + + rc = fsi_master_read(master, link, id, 0, &chip_id, sizeof(chip_id)); + if (rc) { + dev_dbg(&master->dev, "can't read slave %02x:%02x %d\n", + link, id, rc); + return -ENODEV; + } + chip_id = be32_to_cpu(chip_id); + + crc = crc4(0, chip_id, 32); + if (crc) { + dev_warn(&master->dev, "slave %02x:%02x invalid chip id CRC!\n", + link, id); + return -EIO; + } + + dev_info(&master->dev, "fsi: found chip %08x at %02x:%02x:%02x\n", + chip_id, master->idx, link, id); + + rc = fsi_slave_set_smode(master, link, id); + if (rc) { + dev_warn(&master->dev, + "can't set smode on slave:%02x:%02x %d\n", + link, id, rc); + return -ENODEV; + } + + /* If we're behind a master that doesn't provide a self-running bus + * clock, put the slave into async mode + */ + if (master->flags & FSI_MASTER_FLAG_SWCLOCK) { + llmode = cpu_to_be32(FSI_LLMODE_ASYNC); + rc = fsi_master_write(master, link, id, + FSI_SLAVE_BASE + FSI_LLMODE, + &llmode, sizeof(llmode)); + if (rc) + dev_warn(&master->dev, + "can't set llmode on slave:%02x:%02x %d\n", + link, id, rc); + } + + /* We can communicate with a slave; create the slave device and + * register. + */ + slave = kzalloc(sizeof(*slave), GFP_KERNEL); + if (!slave) + return -ENOMEM; + + slave->master = master; + slave->dev.parent = &master->dev; + slave->dev.release = fsi_slave_release; + slave->link = link; + slave->id = id; + slave->size = FSI_SLAVE_SIZE_23b; + + dev_set_name(&slave->dev, "slave@%02x:%02x", link, id); + rc = device_register(&slave->dev); + if (rc < 0) { + dev_warn(&master->dev, "failed to create slave device: %d\n", + rc); + put_device(&slave->dev); + return rc; + } + + rc = device_create_bin_file(&slave->dev, &fsi_slave_raw_attr); + if (rc) + dev_warn(&slave->dev, "failed to create raw attr: %d\n", rc); + + rc = device_create_bin_file(&slave->dev, &fsi_slave_term_attr); + if (rc) + dev_warn(&slave->dev, "failed to create term attr: %d\n", rc); + + rc = fsi_slave_scan(slave); + if (rc) + dev_dbg(&master->dev, "failed during slave scan with: %d\n", + rc); + + return rc; +} + +/* FSI master support */ +static int fsi_check_access(uint32_t addr, size_t size) +{ + if (size != 1 && size != 2 && size != 4) + return -EINVAL; + + if ((addr & 0x3) != (size & 0x3)) + return -EINVAL; + + return 0; +} + +static int fsi_master_read(struct fsi_master *master, int link, + uint8_t slave_id, uint32_t addr, void *val, size_t size) +{ + int rc; + + trace_fsi_master_read(master, link, slave_id, addr, size); + + rc = fsi_check_access(addr, size); + if (!rc) + rc = master->read(master, link, slave_id, addr, val, size); + + trace_fsi_master_rw_result(master, link, slave_id, addr, size, + false, val, rc); + + return rc; +} + +static int fsi_master_write(struct fsi_master *master, int link, + uint8_t slave_id, uint32_t addr, const void *val, size_t size) +{ + int rc; + + trace_fsi_master_write(master, link, slave_id, addr, size, val); + + rc = fsi_check_access(addr, size); + if (!rc) + rc = master->write(master, link, slave_id, addr, val, size); + + trace_fsi_master_rw_result(master, link, slave_id, addr, size, + true, val, rc); + + return rc; +} + +static int fsi_master_link_enable(struct fsi_master *master, int link) +{ + if (master->link_enable) + return master->link_enable(master, link); + + return 0; +} + +/* + * Issue a break command on this link + */ +static int fsi_master_break(struct fsi_master *master, int link) +{ + trace_fsi_master_break(master, link); + + if (master->send_break) + return master->send_break(master, link); + + return 0; +} + +static int fsi_master_scan(struct fsi_master *master) +{ + int link, rc; + + for (link = 0; link < master->n_links; link++) { + rc = fsi_master_link_enable(master, link); + if (rc) { + dev_dbg(&master->dev, + "enable link %d failed: %d\n", link, rc); + continue; + } + rc = fsi_master_break(master, link); + if (rc) { + dev_dbg(&master->dev, + "break to link %d failed: %d\n", link, rc); + continue; + } + + fsi_slave_init(master, link, 0); + } + + return 0; +} + +static int fsi_slave_remove_device(struct device *dev, void *arg) +{ + device_unregister(dev); + return 0; +} + +static int fsi_master_remove_slave(struct device *dev, void *arg) +{ + device_for_each_child(dev, NULL, fsi_slave_remove_device); + device_unregister(dev); + return 0; +} + +static void fsi_master_unscan(struct fsi_master *master) +{ + device_for_each_child(&master->dev, NULL, fsi_master_remove_slave); +} + +static ssize_t master_rescan_store(struct device *dev, + struct device_attribute *attr, const char *buf, size_t count) +{ + struct fsi_master *master = to_fsi_master(dev); + int rc; + + fsi_master_unscan(master); + rc = fsi_master_scan(master); + if (rc < 0) + return rc; + + return count; +} + +static DEVICE_ATTR(rescan, 0200, NULL, master_rescan_store); + +static ssize_t master_break_store(struct device *dev, + struct device_attribute *attr, const char *buf, size_t count) +{ + struct fsi_master *master = to_fsi_master(dev); + + fsi_master_break(master, 0); + + return count; +} + +static DEVICE_ATTR(break, 0200, NULL, master_break_store); + +int fsi_master_register(struct fsi_master *master) +{ + int rc; + + if (!master) + return -EINVAL; + + master->idx = ida_simple_get(&master_ida, 0, INT_MAX, GFP_KERNEL); + dev_set_name(&master->dev, "fsi%d", master->idx); + + rc = device_register(&master->dev); + if (rc) { + ida_simple_remove(&master_ida, master->idx); + return rc; + } + + rc = device_create_file(&master->dev, &dev_attr_rescan); + if (rc) { + device_unregister(&master->dev); + ida_simple_remove(&master_ida, master->idx); + return rc; + } + + rc = device_create_file(&master->dev, &dev_attr_break); + if (rc) { + device_unregister(&master->dev); + ida_simple_remove(&master_ida, master->idx); + return rc; + } + + fsi_master_scan(master); + + return 0; +} +EXPORT_SYMBOL_GPL(fsi_master_register); + +void fsi_master_unregister(struct fsi_master *master) +{ + if (master->idx >= 0) { + ida_simple_remove(&master_ida, master->idx); + master->idx = -1; + } + + fsi_master_unscan(master); + device_unregister(&master->dev); +} +EXPORT_SYMBOL_GPL(fsi_master_unregister); /* FSI core & Linux bus type definitions */ @@ -39,6 +860,23 @@ static int fsi_bus_match(struct device *dev, struct device_driver *drv) return 0; } +int fsi_driver_register(struct fsi_driver *fsi_drv) +{ + if (!fsi_drv) + return -EINVAL; + if (!fsi_drv->id_table) + return -EINVAL; + + return driver_register(&fsi_drv->drv); +} +EXPORT_SYMBOL_GPL(fsi_driver_register); + +void fsi_driver_unregister(struct fsi_driver *fsi_drv) +{ + driver_unregister(&fsi_drv->drv); +} +EXPORT_SYMBOL_GPL(fsi_driver_unregister); + struct bus_type fsi_bus_type = { .name = "fsi", .match = fsi_bus_match, @@ -57,3 +895,6 @@ static void fsi_exit(void) module_init(fsi_init); module_exit(fsi_exit); +module_param(discard_errors, int, 0664); +MODULE_LICENSE("GPL"); +MODULE_PARM_DESC(discard_errors, "Don't invoke error handling on bus accesses"); |