diff options
Diffstat (limited to 'arch/arm/mach-tegra/ivc.c')
| -rw-r--r-- | arch/arm/mach-tegra/ivc.c | 553 |
1 files changed, 553 insertions, 0 deletions
diff --git a/arch/arm/mach-tegra/ivc.c b/arch/arm/mach-tegra/ivc.c new file mode 100644 index 0000000000..cf6626fb12 --- /dev/null +++ b/arch/arm/mach-tegra/ivc.c @@ -0,0 +1,553 @@ +/* + * Copyright (c) 2016, NVIDIA CORPORATION. + * + * SPDX-License-Identifier: GPL-2.0 + */ + +#include <common.h> +#include <asm/io.h> +#include <asm/arch-tegra/ivc.h> + +#define TEGRA_IVC_ALIGN 64 + +/* + * IVC channel reset protocol. + * + * Each end uses its tx_channel.state to indicate its synchronization state. + */ +enum ivc_state { + /* + * This value is zero for backwards compatibility with services that + * assume channels to be initially zeroed. Such channels are in an + * initially valid state, but cannot be asynchronously reset, and must + * maintain a valid state at all times. + * + * The transmitting end can enter the established state from the sync or + * ack state when it observes the receiving endpoint in the ack or + * established state, indicating that has cleared the counters in our + * rx_channel. + */ + ivc_state_established = 0, + + /* + * If an endpoint is observed in the sync state, the remote endpoint is + * allowed to clear the counters it owns asynchronously with respect to + * the current endpoint. Therefore, the current endpoint is no longer + * allowed to communicate. + */ + ivc_state_sync, + + /* + * When the transmitting end observes the receiving end in the sync + * state, it can clear the w_count and r_count and transition to the ack + * state. If the remote endpoint observes us in the ack state, it can + * return to the established state once it has cleared its counters. + */ + ivc_state_ack +}; + +/* + * This structure is divided into two-cache aligned parts, the first is only + * written through the tx_channel pointer, while the second is only written + * through the rx_channel pointer. This delineates ownership of the cache lines, + * which is critical to performance and necessary in non-cache coherent + * implementations. + */ +struct tegra_ivc_channel_header { + union { + /* fields owned by the transmitting end */ + struct { + uint32_t w_count; + uint32_t state; + }; + uint8_t w_align[TEGRA_IVC_ALIGN]; + }; + union { + /* fields owned by the receiving end */ + uint32_t r_count; + uint8_t r_align[TEGRA_IVC_ALIGN]; + }; +}; + +static inline void tegra_ivc_invalidate_counter(struct tegra_ivc *ivc, + struct tegra_ivc_channel_header *h, + ulong offset) +{ + ulong base = ((ulong)h) + offset; + invalidate_dcache_range(base, base + TEGRA_IVC_ALIGN); +} + +static inline void tegra_ivc_flush_counter(struct tegra_ivc *ivc, + struct tegra_ivc_channel_header *h, + ulong offset) +{ + ulong base = ((ulong)h) + offset; + flush_dcache_range(base, base + TEGRA_IVC_ALIGN); +} + +static inline ulong tegra_ivc_frame_addr(struct tegra_ivc *ivc, + struct tegra_ivc_channel_header *h, + uint32_t frame) +{ + BUG_ON(frame >= ivc->nframes); + + return ((ulong)h) + sizeof(struct tegra_ivc_channel_header) + + (ivc->frame_size * frame); +} + +static inline void *tegra_ivc_frame_pointer(struct tegra_ivc *ivc, + struct tegra_ivc_channel_header *ch, + uint32_t frame) +{ + return (void *)tegra_ivc_frame_addr(ivc, ch, frame); +} + +static inline void tegra_ivc_invalidate_frame(struct tegra_ivc *ivc, + struct tegra_ivc_channel_header *h, + unsigned frame) +{ + ulong base = tegra_ivc_frame_addr(ivc, h, frame); + invalidate_dcache_range(base, base + ivc->frame_size); +} + +static inline void tegra_ivc_flush_frame(struct tegra_ivc *ivc, + struct tegra_ivc_channel_header *h, + unsigned frame) +{ + ulong base = tegra_ivc_frame_addr(ivc, h, frame); + flush_dcache_range(base, base + ivc->frame_size); +} + +static inline int tegra_ivc_channel_empty(struct tegra_ivc *ivc, + struct tegra_ivc_channel_header *ch) +{ + /* + * This function performs multiple checks on the same values with + * security implications, so create snapshots with ACCESS_ONCE() to + * ensure that these checks use the same values. + */ + uint32_t w_count = ACCESS_ONCE(ch->w_count); + uint32_t r_count = ACCESS_ONCE(ch->r_count); + + /* + * Perform an over-full check to prevent denial of service attacks where + * a server could be easily fooled into believing that there's an + * extremely large number of frames ready, since receivers are not + * expected to check for full or over-full conditions. + * + * Although the channel isn't empty, this is an invalid case caused by + * a potentially malicious peer, so returning empty is safer, because it + * gives the impression that the channel has gone silent. + */ + if (w_count - r_count > ivc->nframes) + return 1; + + return w_count == r_count; +} + +static inline int tegra_ivc_channel_full(struct tegra_ivc *ivc, + struct tegra_ivc_channel_header *ch) +{ + /* + * Invalid cases where the counters indicate that the queue is over + * capacity also appear full. + */ + return (ACCESS_ONCE(ch->w_count) - ACCESS_ONCE(ch->r_count)) >= + ivc->nframes; +} + +static inline void tegra_ivc_advance_rx(struct tegra_ivc *ivc) +{ + ACCESS_ONCE(ivc->rx_channel->r_count) = + ACCESS_ONCE(ivc->rx_channel->r_count) + 1; + + if (ivc->r_pos == ivc->nframes - 1) + ivc->r_pos = 0; + else + ivc->r_pos++; +} + +static inline void tegra_ivc_advance_tx(struct tegra_ivc *ivc) +{ + ACCESS_ONCE(ivc->tx_channel->w_count) = + ACCESS_ONCE(ivc->tx_channel->w_count) + 1; + + if (ivc->w_pos == ivc->nframes - 1) + ivc->w_pos = 0; + else + ivc->w_pos++; +} + +static inline int tegra_ivc_check_read(struct tegra_ivc *ivc) +{ + ulong offset; + + /* + * tx_channel->state is set locally, so it is not synchronized with + * state from the remote peer. The remote peer cannot reset its + * transmit counters until we've acknowledged its synchronization + * request, so no additional synchronization is required because an + * asynchronous transition of rx_channel->state to ivc_state_ack is not + * allowed. + */ + if (ivc->tx_channel->state != ivc_state_established) + return -ECONNRESET; + + /* + * Avoid unnecessary invalidations when performing repeated accesses to + * an IVC channel by checking the old queue pointers first. + * Synchronization is only necessary when these pointers indicate empty + * or full. + */ + if (!tegra_ivc_channel_empty(ivc, ivc->rx_channel)) + return 0; + + offset = offsetof(struct tegra_ivc_channel_header, w_count); + tegra_ivc_invalidate_counter(ivc, ivc->rx_channel, offset); + return tegra_ivc_channel_empty(ivc, ivc->rx_channel) ? -ENOMEM : 0; +} + +static inline int tegra_ivc_check_write(struct tegra_ivc *ivc) +{ + ulong offset; + + if (ivc->tx_channel->state != ivc_state_established) + return -ECONNRESET; + + if (!tegra_ivc_channel_full(ivc, ivc->tx_channel)) + return 0; + + offset = offsetof(struct tegra_ivc_channel_header, r_count); + tegra_ivc_invalidate_counter(ivc, ivc->tx_channel, offset); + return tegra_ivc_channel_full(ivc, ivc->tx_channel) ? -ENOMEM : 0; +} + +static inline uint32_t tegra_ivc_channel_avail_count(struct tegra_ivc *ivc, + struct tegra_ivc_channel_header *ch) +{ + /* + * This function isn't expected to be used in scenarios where an + * over-full situation can lead to denial of service attacks. See the + * comment in tegra_ivc_channel_empty() for an explanation about + * special over-full considerations. + */ + return ACCESS_ONCE(ch->w_count) - ACCESS_ONCE(ch->r_count); +} + +int tegra_ivc_read_get_next_frame(struct tegra_ivc *ivc, void **frame) +{ + int result = tegra_ivc_check_read(ivc); + if (result < 0) + return result; + + /* + * Order observation of w_pos potentially indicating new data before + * data read. + */ + mb(); + + tegra_ivc_invalidate_frame(ivc, ivc->rx_channel, ivc->r_pos); + *frame = tegra_ivc_frame_pointer(ivc, ivc->rx_channel, ivc->r_pos); + + return 0; +} + +int tegra_ivc_read_advance(struct tegra_ivc *ivc) +{ + ulong offset; + int result; + + /* + * No read barriers or synchronization here: the caller is expected to + * have already observed the channel non-empty. This check is just to + * catch programming errors. + */ + result = tegra_ivc_check_read(ivc); + if (result) + return result; + + tegra_ivc_advance_rx(ivc); + offset = offsetof(struct tegra_ivc_channel_header, r_count); + tegra_ivc_flush_counter(ivc, ivc->rx_channel, offset); + + /* + * Ensure our write to r_pos occurs before our read from w_pos. + */ + mb(); + + offset = offsetof(struct tegra_ivc_channel_header, w_count); + tegra_ivc_invalidate_counter(ivc, ivc->rx_channel, offset); + + if (tegra_ivc_channel_avail_count(ivc, ivc->rx_channel) == + ivc->nframes - 1) + ivc->notify(ivc); + + return 0; +} + +int tegra_ivc_write_get_next_frame(struct tegra_ivc *ivc, void **frame) +{ + int result = tegra_ivc_check_write(ivc); + if (result) + return result; + + *frame = tegra_ivc_frame_pointer(ivc, ivc->tx_channel, ivc->w_pos); + + return 0; +} + +int tegra_ivc_write_advance(struct tegra_ivc *ivc) +{ + ulong offset; + int result; + + result = tegra_ivc_check_write(ivc); + if (result) + return result; + + tegra_ivc_flush_frame(ivc, ivc->tx_channel, ivc->w_pos); + + /* + * Order any possible stores to the frame before update of w_pos. + */ + mb(); + + tegra_ivc_advance_tx(ivc); + offset = offsetof(struct tegra_ivc_channel_header, w_count); + tegra_ivc_flush_counter(ivc, ivc->tx_channel, offset); + + /* + * Ensure our write to w_pos occurs before our read from r_pos. + */ + mb(); + + offset = offsetof(struct tegra_ivc_channel_header, r_count); + tegra_ivc_invalidate_counter(ivc, ivc->tx_channel, offset); + + if (tegra_ivc_channel_avail_count(ivc, ivc->tx_channel) == 1) + ivc->notify(ivc); + + return 0; +} + +/* + * =============================================================== + * IVC State Transition Table - see tegra_ivc_channel_notified() + * =============================================================== + * + * local remote action + * ----- ------ ----------------------------------- + * SYNC EST <none> + * SYNC ACK reset counters; move to EST; notify + * SYNC SYNC reset counters; move to ACK; notify + * ACK EST move to EST; notify + * ACK ACK move to EST; notify + * ACK SYNC reset counters; move to ACK; notify + * EST EST <none> + * EST ACK <none> + * EST SYNC reset counters; move to ACK; notify + * + * =============================================================== + */ +int tegra_ivc_channel_notified(struct tegra_ivc *ivc) +{ + ulong offset; + enum ivc_state peer_state; + + /* Copy the receiver's state out of shared memory. */ + offset = offsetof(struct tegra_ivc_channel_header, w_count); + tegra_ivc_invalidate_counter(ivc, ivc->rx_channel, offset); + peer_state = ACCESS_ONCE(ivc->rx_channel->state); + + if (peer_state == ivc_state_sync) { + /* + * Order observation of ivc_state_sync before stores clearing + * tx_channel. + */ + mb(); + + /* + * Reset tx_channel counters. The remote end is in the SYNC + * state and won't make progress until we change our state, + * so the counters are not in use at this time. + */ + ivc->tx_channel->w_count = 0; + ivc->rx_channel->r_count = 0; + + ivc->w_pos = 0; + ivc->r_pos = 0; + + /* + * Ensure that counters appear cleared before new state can be + * observed. + */ + mb(); + + /* + * Move to ACK state. We have just cleared our counters, so it + * is now safe for the remote end to start using these values. + */ + ivc->tx_channel->state = ivc_state_ack; + offset = offsetof(struct tegra_ivc_channel_header, w_count); + tegra_ivc_flush_counter(ivc, ivc->tx_channel, offset); + + /* + * Notify remote end to observe state transition. + */ + ivc->notify(ivc); + } else if (ivc->tx_channel->state == ivc_state_sync && + peer_state == ivc_state_ack) { + /* + * Order observation of ivc_state_sync before stores clearing + * tx_channel. + */ + mb(); + + /* + * Reset tx_channel counters. The remote end is in the ACK + * state and won't make progress until we change our state, + * so the counters are not in use at this time. + */ + ivc->tx_channel->w_count = 0; + ivc->rx_channel->r_count = 0; + + ivc->w_pos = 0; + ivc->r_pos = 0; + + /* + * Ensure that counters appear cleared before new state can be + * observed. + */ + mb(); + + /* + * Move to ESTABLISHED state. We know that the remote end has + * already cleared its counters, so it is safe to start + * writing/reading on this channel. + */ + ivc->tx_channel->state = ivc_state_established; + offset = offsetof(struct tegra_ivc_channel_header, w_count); + tegra_ivc_flush_counter(ivc, ivc->tx_channel, offset); + + /* + * Notify remote end to observe state transition. + */ + ivc->notify(ivc); + } else if (ivc->tx_channel->state == ivc_state_ack) { + /* + * At this point, we have observed the peer to be in either + * the ACK or ESTABLISHED state. Next, order observation of + * peer state before storing to tx_channel. + */ + mb(); + + /* + * Move to ESTABLISHED state. We know that we have previously + * cleared our counters, and we know that the remote end has + * cleared its counters, so it is safe to start writing/reading + * on this channel. + */ + ivc->tx_channel->state = ivc_state_established; + offset = offsetof(struct tegra_ivc_channel_header, w_count); + tegra_ivc_flush_counter(ivc, ivc->tx_channel, offset); + + /* + * Notify remote end to observe state transition. + */ + ivc->notify(ivc); + } else { + /* + * There is no need to handle any further action. Either the + * channel is already fully established, or we are waiting for + * the remote end to catch up with our current state. Refer + * to the diagram in "IVC State Transition Table" above. + */ + } + + if (ivc->tx_channel->state != ivc_state_established) + return -EAGAIN; + + return 0; +} + +void tegra_ivc_channel_reset(struct tegra_ivc *ivc) +{ + ulong offset; + + ivc->tx_channel->state = ivc_state_sync; + offset = offsetof(struct tegra_ivc_channel_header, w_count); + tegra_ivc_flush_counter(ivc, ivc->tx_channel, offset); + ivc->notify(ivc); +} + +static int check_ivc_params(ulong qbase1, ulong qbase2, uint32_t nframes, + uint32_t frame_size) +{ + int ret = 0; + + BUG_ON(offsetof(struct tegra_ivc_channel_header, w_count) & + (TEGRA_IVC_ALIGN - 1)); + BUG_ON(offsetof(struct tegra_ivc_channel_header, r_count) & + (TEGRA_IVC_ALIGN - 1)); + BUG_ON(sizeof(struct tegra_ivc_channel_header) & + (TEGRA_IVC_ALIGN - 1)); + + if ((uint64_t)nframes * (uint64_t)frame_size >= 0x100000000) { + error("tegra_ivc: nframes * frame_size overflows\n"); + return -EINVAL; + } + + /* + * The headers must at least be aligned enough for counters + * to be accessed atomically. + */ + if ((qbase1 & (TEGRA_IVC_ALIGN - 1)) || + (qbase2 & (TEGRA_IVC_ALIGN - 1))) { + error("tegra_ivc: channel start not aligned\n"); + return -EINVAL; + } + + if (frame_size & (TEGRA_IVC_ALIGN - 1)) { + error("tegra_ivc: frame size not adequately aligned\n"); + return -EINVAL; + } + + if (qbase1 < qbase2) { + if (qbase1 + frame_size * nframes > qbase2) + ret = -EINVAL; + } else { + if (qbase2 + frame_size * nframes > qbase1) + ret = -EINVAL; + } + + if (ret) { + error("tegra_ivc: queue regions overlap\n"); + return ret; + } + + return 0; +} + +int tegra_ivc_init(struct tegra_ivc *ivc, ulong rx_base, ulong tx_base, + uint32_t nframes, uint32_t frame_size, + void (*notify)(struct tegra_ivc *)) +{ + int ret; + + if (!ivc) + return -EINVAL; + + ret = check_ivc_params(rx_base, tx_base, nframes, frame_size); + if (ret) + return ret; + + ivc->rx_channel = (struct tegra_ivc_channel_header *)rx_base; + ivc->tx_channel = (struct tegra_ivc_channel_header *)tx_base; + ivc->w_pos = 0; + ivc->r_pos = 0; + ivc->nframes = nframes; + ivc->frame_size = frame_size; + ivc->notify = notify; + + return 0; +} |