u-boot/arch/arm/mach-tegra/ivc.c

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/*
* 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;
}