diff options
Diffstat (limited to 'drivers/firmware')
| -rw-r--r-- | drivers/firmware/arm_scmi/common.h | 32 | ||||
| -rw-r--r-- | drivers/firmware/arm_scmi/driver.c | 254 |
2 files changed, 251 insertions, 35 deletions
diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h index 9454488021ea..651af0c7bed9 100644 --- a/drivers/firmware/arm_scmi/common.h +++ b/drivers/firmware/arm_scmi/common.h @@ -14,6 +14,8 @@ #include <linux/device.h> #include <linux/errno.h> #include <linux/kernel.h> +#include <linux/hashtable.h> +#include <linux/list.h> #include <linux/module.h> #include <linux/scmi_protocol.h> #include <linux/types.h> @@ -65,6 +67,16 @@ struct scmi_msg_resp_prot_version { #define MSG_XTRACT_TOKEN(hdr) FIELD_GET(MSG_TOKEN_ID_MASK, (hdr)) #define MSG_TOKEN_MAX (MSG_XTRACT_TOKEN(MSG_TOKEN_ID_MASK) + 1) +/* + * Size of @pending_xfers hashtable included in @scmi_xfers_info; ideally, in + * order to minimize space and collisions, this should equal max_msg, i.e. the + * maximum number of in-flight messages on a specific platform, but such value + * is only available at runtime while kernel hashtables are statically sized: + * pick instead as a fixed static size the maximum number of entries that can + * fit the whole table into one 4k page. + */ +#define SCMI_PENDING_XFERS_HT_ORDER_SZ 9 + /** * struct scmi_msg_hdr - Message(Tx/Rx) header * @@ -138,6 +150,9 @@ struct scmi_msg { * buffer for the rx path as we use for the tx path. * @done: command message transmit completion event * @async_done: pointer to delayed response message received event completion + * @pending: True for xfers added to @pending_xfers hashtable + * @node: An hlist_node reference used to store this xfer, alternatively, on + * the free list @free_xfers or in the @pending_xfers hashtable */ struct scmi_xfer { int transfer_id; @@ -146,8 +161,25 @@ struct scmi_xfer { struct scmi_msg rx; struct completion done; struct completion *async_done; + bool pending; + struct hlist_node node; }; +/* + * An helper macro to lookup an xfer from the @pending_xfers hashtable + * using the message sequence number token as a key. + */ +#define XFER_FIND(__ht, __k) \ +({ \ + typeof(__k) k_ = __k; \ + struct scmi_xfer *xfer_ = NULL; \ + \ + hash_for_each_possible((__ht), xfer_, node, k_) \ + if (xfer_->hdr.seq == k_) \ + break; \ + xfer_; \ +}) + struct scmi_xfer_ops; /** diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c index 374bf97a7b4a..3c99390f9415 100644 --- a/drivers/firmware/arm_scmi/driver.c +++ b/drivers/firmware/arm_scmi/driver.c @@ -21,6 +21,7 @@ #include <linux/io.h> #include <linux/kernel.h> #include <linux/ktime.h> +#include <linux/hashtable.h> #include <linux/list.h> #include <linux/module.h> #include <linux/of_address.h> @@ -67,16 +68,21 @@ struct scmi_requested_dev { /** * struct scmi_xfers_info - Structure to manage transfer information * - * @xfer_block: Preallocated Message array * @xfer_alloc_table: Bitmap table for allocated messages. * Index of this bitmap table is also used for message * sequence identifier. * @xfer_lock: Protection for message allocation + * @free_xfers: A free list for available to use xfers. It is initialized with + * a number of xfers equal to the maximum allowed in-flight + * messages. + * @pending_xfers: An hashtable, indexed by msg_hdr.seq, used to keep all the + * currently in-flight messages. */ struct scmi_xfers_info { - struct scmi_xfer *xfer_block; unsigned long *xfer_alloc_table; spinlock_t xfer_lock; + struct hlist_head free_xfers; + DECLARE_HASHTABLE(pending_xfers, SCMI_PENDING_XFERS_HT_ORDER_SZ); }; /** @@ -192,45 +198,184 @@ void *scmi_notification_instance_data_get(const struct scmi_handle *handle) } /** + * scmi_xfer_token_set - Reserve and set new token for the xfer at hand + * + * @minfo: Pointer to Tx/Rx Message management info based on channel type + * @xfer: The xfer to act upon + * + * Pick the next unused monotonically increasing token and set it into + * xfer->hdr.seq: picking a monotonically increasing value avoids immediate + * reuse of freshly completed or timed-out xfers, thus mitigating the risk + * of incorrect association of a late and expired xfer with a live in-flight + * transaction, both happening to re-use the same token identifier. + * + * Since platform is NOT required to answer our request in-order we should + * account for a few rare but possible scenarios: + * + * - exactly 'next_token' may be NOT available so pick xfer_id >= next_token + * using find_next_zero_bit() starting from candidate next_token bit + * + * - all tokens ahead upto (MSG_TOKEN_ID_MASK - 1) are used in-flight but we + * are plenty of free tokens at start, so try a second pass using + * find_next_zero_bit() and starting from 0. + * + * X = used in-flight + * + * Normal + * ------ + * + * |- xfer_id picked + * -----------+---------------------------------------------------------- + * | | |X|X|X| | | | | | ... ... ... ... ... ... ... ... ... ... ...|X|X| + * ---------------------------------------------------------------------- + * ^ + * |- next_token + * + * Out-of-order pending at start + * ----------------------------- + * + * |- xfer_id picked, last_token fixed + * -----+---------------------------------------------------------------- + * |X|X| | | | |X|X| ... ... ... ... ... ... ... ... ... ... ... ...|X| | + * ---------------------------------------------------------------------- + * ^ + * |- next_token + * + * + * Out-of-order pending at end + * --------------------------- + * + * |- xfer_id picked, last_token fixed + * -----+---------------------------------------------------------------- + * |X|X| | | | |X|X| ... ... ... ... ... ... ... ... ... ... |X|X|X||X|X| + * ---------------------------------------------------------------------- + * ^ + * |- next_token + * + * Context: Assumes to be called with @xfer_lock already acquired. + * + * Return: 0 on Success or error + */ +static int scmi_xfer_token_set(struct scmi_xfers_info *minfo, + struct scmi_xfer *xfer) +{ + unsigned long xfer_id, next_token; + + /* + * Pick a candidate monotonic token in range [0, MSG_TOKEN_MAX - 1] + * using the pre-allocated transfer_id as a base. + * Note that the global transfer_id is shared across all message types + * so there could be holes in the allocated set of monotonic sequence + * numbers, but that is going to limit the effectiveness of the + * mitigation only in very rare limit conditions. + */ + next_token = (xfer->transfer_id & (MSG_TOKEN_MAX - 1)); + + /* Pick the next available xfer_id >= next_token */ + xfer_id = find_next_zero_bit(minfo->xfer_alloc_table, + MSG_TOKEN_MAX, next_token); + if (xfer_id == MSG_TOKEN_MAX) { + /* + * After heavily out-of-order responses, there are no free + * tokens ahead, but only at start of xfer_alloc_table so + * try again from the beginning. + */ + xfer_id = find_next_zero_bit(minfo->xfer_alloc_table, + MSG_TOKEN_MAX, 0); + /* + * Something is wrong if we got here since there can be a + * maximum number of (MSG_TOKEN_MAX - 1) in-flight messages + * but we have not found any free token [0, MSG_TOKEN_MAX - 1]. + */ + if (WARN_ON_ONCE(xfer_id == MSG_TOKEN_MAX)) + return -ENOMEM; + } + + /* Update +/- last_token accordingly if we skipped some hole */ + if (xfer_id != next_token) + atomic_add((int)(xfer_id - next_token), &transfer_last_id); + + /* Set in-flight */ + set_bit(xfer_id, minfo->xfer_alloc_table); + xfer->hdr.seq = (u16)xfer_id; + + return 0; +} + +/** + * scmi_xfer_token_clear - Release the token + * + * @minfo: Pointer to Tx/Rx Message management info based on channel type + * @xfer: The xfer to act upon + */ +static inline void scmi_xfer_token_clear(struct scmi_xfers_info *minfo, + struct scmi_xfer *xfer) +{ + clear_bit(xfer->hdr.seq, minfo->xfer_alloc_table); +} + +/** * scmi_xfer_get() - Allocate one message * * @handle: Pointer to SCMI entity handle * @minfo: Pointer to Tx/Rx Message management info based on channel type + * @set_pending: If true a monotonic token is picked and the xfer is added to + * the pending hash table. * * Helper function which is used by various message functions that are * exposed to clients of this driver for allocating a message traffic event. * - * This function can sleep depending on pending requests already in the system - * for the SCMI entity. Further, this also holds a spinlock to maintain - * integrity of internal data structures. + * Picks an xfer from the free list @free_xfers (if any available) and, if + * required, sets a monotonically increasing token and stores the inflight xfer + * into the @pending_xfers hashtable for later retrieval. + * + * The successfully initialized xfer is refcounted. + * + * Context: Holds @xfer_lock while manipulating @xfer_alloc_table and + * @free_xfers. * * Return: 0 if all went fine, else corresponding error. */ static struct scmi_xfer *scmi_xfer_get(const struct scmi_handle *handle, - struct scmi_xfers_info *minfo) + struct scmi_xfers_info *minfo, + bool set_pending) { - u16 xfer_id; + int ret; + unsigned long flags; struct scmi_xfer *xfer; - unsigned long flags, bit_pos; - struct scmi_info *info = handle_to_scmi_info(handle); - /* Keep the locked section as small as possible */ spin_lock_irqsave(&minfo->xfer_lock, flags); - bit_pos = find_first_zero_bit(minfo->xfer_alloc_table, - info->desc->max_msg); - if (bit_pos == info->desc->max_msg) { + if (hlist_empty(&minfo->free_xfers)) { spin_unlock_irqrestore(&minfo->xfer_lock, flags); return ERR_PTR(-ENOMEM); } - set_bit(bit_pos, minfo->xfer_alloc_table); - spin_unlock_irqrestore(&minfo->xfer_lock, flags); - xfer_id = bit_pos; + /* grab an xfer from the free_list */ + xfer = hlist_entry(minfo->free_xfers.first, struct scmi_xfer, node); + hlist_del_init(&xfer->node); - xfer = &minfo->xfer_block[xfer_id]; - xfer->hdr.seq = xfer_id; + /* + * Allocate transfer_id early so that can be used also as base for + * monotonic sequence number generation if needed. + */ xfer->transfer_id = atomic_inc_return(&transfer_last_id); + if (set_pending) { + /* Pick and set monotonic token */ + ret = scmi_xfer_token_set(minfo, xfer); + if (!ret) { + hash_add(minfo->pending_xfers, &xfer->node, + xfer->hdr.seq); + xfer->pending = true; + } else { + dev_err(handle->dev, + "Failed to get monotonic token %d\n", ret); + hlist_add_head(&xfer->node, &minfo->free_xfers); + xfer = ERR_PTR(ret); + } + } + spin_unlock_irqrestore(&minfo->xfer_lock, flags); + return xfer; } @@ -240,6 +385,9 @@ static struct scmi_xfer *scmi_xfer_get(const struct scmi_handle *handle, * @minfo: Pointer to Tx/Rx Message management info based on channel type * @xfer: message that was reserved by scmi_xfer_get * + * After refcount check, possibly release an xfer, clearing the token slot, + * removing xfer from @pending_xfers and putting it back into free_xfers. + * * This holds a spinlock to maintain integrity of internal data structures. */ static void @@ -247,16 +395,39 @@ __scmi_xfer_put(struct scmi_xfers_info *minfo, struct scmi_xfer *xfer) { unsigned long flags; - /* - * Keep the locked section as small as possible - * NOTE: we might escape with smp_mb and no lock here.. - * but just be conservative and symmetric. - */ spin_lock_irqsave(&minfo->xfer_lock, flags); - clear_bit(xfer->hdr.seq, minfo->xfer_alloc_table); + if (xfer->pending) { + scmi_xfer_token_clear(minfo, xfer); + hash_del(&xfer->node); + xfer->pending = false; + } + hlist_add_head(&xfer->node, &minfo->free_xfers); spin_unlock_irqrestore(&minfo->xfer_lock, flags); } +/** + * scmi_xfer_lookup_unlocked - Helper to lookup an xfer_id + * + * @minfo: Pointer to Tx/Rx Message management info based on channel type + * @xfer_id: Token ID to lookup in @pending_xfers + * + * Refcounting is untouched. + * + * Context: Assumes to be called with @xfer_lock already acquired. + * + * Return: A valid xfer on Success or error otherwise + */ +static struct scmi_xfer * +scmi_xfer_lookup_unlocked(struct scmi_xfers_info *minfo, u16 xfer_id) +{ + struct scmi_xfer *xfer = NULL; + + if (test_bit(xfer_id, minfo->xfer_alloc_table)) + xfer = XFER_FIND(minfo->pending_xfers, xfer_id); + + return xfer ?: ERR_PTR(-EINVAL); +} + static void scmi_handle_notification(struct scmi_chan_info *cinfo, u32 msg_hdr) { struct scmi_xfer *xfer; @@ -266,7 +437,7 @@ static void scmi_handle_notification(struct scmi_chan_info *cinfo, u32 msg_hdr) ktime_t ts; ts = ktime_get_boottime(); - xfer = scmi_xfer_get(cinfo->handle, minfo); + xfer = scmi_xfer_get(cinfo->handle, minfo, false); if (IS_ERR(xfer)) { dev_err(dev, "failed to get free message slot (%ld)\n", PTR_ERR(xfer)); @@ -292,19 +463,22 @@ static void scmi_handle_notification(struct scmi_chan_info *cinfo, u32 msg_hdr) static void scmi_handle_response(struct scmi_chan_info *cinfo, u16 xfer_id, u8 msg_type) { + unsigned long flags; struct scmi_xfer *xfer; struct device *dev = cinfo->dev; struct scmi_info *info = handle_to_scmi_info(cinfo->handle); struct scmi_xfers_info *minfo = &info->tx_minfo; /* Are we even expecting this? */ - if (!test_bit(xfer_id, minfo->xfer_alloc_table)) { + spin_lock_irqsave(&minfo->xfer_lock, flags); + xfer = scmi_xfer_lookup_unlocked(minfo, xfer_id); + spin_unlock_irqrestore(&minfo->xfer_lock, flags); + if (IS_ERR(xfer)) { dev_err(dev, "message for %d is not expected!\n", xfer_id); info->desc->ops->clear_channel(cinfo); return; } - xfer = &minfo->xfer_block[xfer_id]; /* * Even if a response was indeed expected on this slot at this point, * a buggy platform could wrongly reply feeding us an unexpected @@ -541,7 +715,7 @@ static int xfer_get_init(const struct scmi_protocol_handle *ph, tx_size > info->desc->max_msg_size) return -ERANGE; - xfer = scmi_xfer_get(pi->handle, minfo); + xfer = scmi_xfer_get(pi->handle, minfo, true); if (IS_ERR(xfer)) { ret = PTR_ERR(xfer); dev_err(dev, "failed to get free message slot(%d)\n", ret); @@ -1018,18 +1192,25 @@ static int __scmi_xfer_info_init(struct scmi_info *sinfo, return -EINVAL; } - info->xfer_block = devm_kcalloc(dev, desc->max_msg, - sizeof(*info->xfer_block), GFP_KERNEL); - if (!info->xfer_block) - return -ENOMEM; + hash_init(info->pending_xfers); - info->xfer_alloc_table = devm_kcalloc(dev, BITS_TO_LONGS(desc->max_msg), + /* Allocate a bitmask sized to hold MSG_TOKEN_MAX tokens */ + info->xfer_alloc_table = devm_kcalloc(dev, BITS_TO_LONGS(MSG_TOKEN_MAX), sizeof(long), GFP_KERNEL); if (!info->xfer_alloc_table) return -ENOMEM; - /* Pre-initialize the buffer pointer to pre-allocated buffers */ - for (i = 0, xfer = info->xfer_block; i < desc->max_msg; i++, xfer++) { + /* + * Preallocate a number of xfers equal to max inflight messages, + * pre-initialize the buffer pointer to pre-allocated buffers and + * attach all of them to the free list + */ + INIT_HLIST_HEAD(&info->free_xfers); + for (i = 0; i < desc->max_msg; i++) { + xfer = devm_kzalloc(dev, sizeof(*xfer), GFP_KERNEL); + if (!xfer) + return -ENOMEM; + xfer->rx.buf = devm_kcalloc(dev, sizeof(u8), desc->max_msg_size, GFP_KERNEL); if (!xfer->rx.buf) @@ -1037,6 +1218,9 @@ static int __scmi_xfer_info_init(struct scmi_info *sinfo, xfer->tx.buf = xfer->rx.buf; init_completion(&xfer->done); + + /* Add initialized xfer to the free list */ + hlist_add_head(&xfer->node, &info->free_xfers); } spin_lock_init(&info->xfer_lock); |