--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Linaro Ltd.
+ * Author: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
+ */
+
+#include <linux/mhi_ep.h>
+#include "internal.h"
+
+size_t mhi_ep_ring_addr2offset(struct mhi_ep_ring *ring, u64 ptr)
+{
+ return (ptr - ring->rbase) / sizeof(struct mhi_ring_element);
+}
+
+static u32 mhi_ep_ring_num_elems(struct mhi_ep_ring *ring)
+{
+ __le64 rlen;
+
+ memcpy_fromio(&rlen, (void __iomem *) &ring->ring_ctx->generic.rlen, sizeof(u64));
+
+ return le64_to_cpu(rlen) / sizeof(struct mhi_ring_element);
+}
+
+void mhi_ep_ring_inc_index(struct mhi_ep_ring *ring)
+{
+ ring->rd_offset = (ring->rd_offset + 1) % ring->ring_size;
+}
+
+static int __mhi_ep_cache_ring(struct mhi_ep_ring *ring, size_t end)
+{
+ struct mhi_ep_cntrl *mhi_cntrl = ring->mhi_cntrl;
+ struct device *dev = &mhi_cntrl->mhi_dev->dev;
+ size_t start, copy_size;
+ int ret;
+
+ /* Don't proceed in the case of event ring. This happens during mhi_ep_ring_start(). */
+ if (ring->type == RING_TYPE_ER)
+ return 0;
+
+ /* No need to cache the ring if write pointer is unmodified */
+ if (ring->wr_offset == end)
+ return 0;
+
+ start = ring->wr_offset;
+ if (start < end) {
+ copy_size = (end - start) * sizeof(struct mhi_ring_element);
+ ret = mhi_cntrl->read_from_host(mhi_cntrl, ring->rbase +
+ (start * sizeof(struct mhi_ring_element)),
+ &ring->ring_cache[start], copy_size);
+ if (ret < 0)
+ return ret;
+ } else {
+ copy_size = (ring->ring_size - start) * sizeof(struct mhi_ring_element);
+ ret = mhi_cntrl->read_from_host(mhi_cntrl, ring->rbase +
+ (start * sizeof(struct mhi_ring_element)),
+ &ring->ring_cache[start], copy_size);
+ if (ret < 0)
+ return ret;
+
+ if (end) {
+ ret = mhi_cntrl->read_from_host(mhi_cntrl, ring->rbase,
+ &ring->ring_cache[0],
+ end * sizeof(struct mhi_ring_element));
+ if (ret < 0)
+ return ret;
+ }
+ }
+
+ dev_dbg(dev, "Cached ring: start %zu end %zu size %zu\n", start, end, copy_size);
+
+ return 0;
+}
+
+static int mhi_ep_cache_ring(struct mhi_ep_ring *ring, u64 wr_ptr)
+{
+ size_t wr_offset;
+ int ret;
+
+ wr_offset = mhi_ep_ring_addr2offset(ring, wr_ptr);
+
+ /* Cache the host ring till write offset */
+ ret = __mhi_ep_cache_ring(ring, wr_offset);
+ if (ret)
+ return ret;
+
+ ring->wr_offset = wr_offset;
+
+ return 0;
+}
+
+int mhi_ep_update_wr_offset(struct mhi_ep_ring *ring)
+{
+ u64 wr_ptr;
+
+ wr_ptr = mhi_ep_mmio_get_db(ring);
+
+ return mhi_ep_cache_ring(ring, wr_ptr);
+}
+
+/* TODO: Support for adding multiple ring elements to the ring */
+int mhi_ep_ring_add_element(struct mhi_ep_ring *ring, struct mhi_ring_element *el)
+{
+ struct mhi_ep_cntrl *mhi_cntrl = ring->mhi_cntrl;
+ struct device *dev = &mhi_cntrl->mhi_dev->dev;
+ size_t old_offset = 0;
+ u32 num_free_elem;
+ __le64 rp;
+ int ret;
+
+ ret = mhi_ep_update_wr_offset(ring);
+ if (ret) {
+ dev_err(dev, "Error updating write pointer\n");
+ return ret;
+ }
+
+ if (ring->rd_offset < ring->wr_offset)
+ num_free_elem = (ring->wr_offset - ring->rd_offset) - 1;
+ else
+ num_free_elem = ((ring->ring_size - ring->rd_offset) + ring->wr_offset) - 1;
+
+ /* Check if there is space in ring for adding at least an element */
+ if (!num_free_elem) {
+ dev_err(dev, "No space left in the ring\n");
+ return -ENOSPC;
+ }
+
+ old_offset = ring->rd_offset;
+ mhi_ep_ring_inc_index(ring);
+
+ dev_dbg(dev, "Adding an element to ring at offset (%zu)\n", ring->rd_offset);
+
+ /* Update rp in ring context */
+ rp = cpu_to_le64(ring->rd_offset * sizeof(*el) + ring->rbase);
+ memcpy_toio((void __iomem *) &ring->ring_ctx->generic.rp, &rp, sizeof(u64));
+
+ ret = mhi_cntrl->write_to_host(mhi_cntrl, el, ring->rbase + (old_offset * sizeof(*el)),
+ sizeof(*el));
+ if (ret < 0)
+ return ret;
+
+ return 0;
+}
+
+void mhi_ep_ring_init(struct mhi_ep_ring *ring, enum mhi_ep_ring_type type, u32 id)
+{
+ ring->type = type;
+ if (ring->type == RING_TYPE_CMD) {
+ ring->db_offset_h = EP_CRDB_HIGHER;
+ ring->db_offset_l = EP_CRDB_LOWER;
+ } else if (ring->type == RING_TYPE_CH) {
+ ring->db_offset_h = CHDB_HIGHER_n(id);
+ ring->db_offset_l = CHDB_LOWER_n(id);
+ ring->ch_id = id;
+ } else {
+ ring->db_offset_h = ERDB_HIGHER_n(id);
+ ring->db_offset_l = ERDB_LOWER_n(id);
+ }
+}
+
+int mhi_ep_ring_start(struct mhi_ep_cntrl *mhi_cntrl, struct mhi_ep_ring *ring,
+ union mhi_ep_ring_ctx *ctx)
+{
+ struct device *dev = &mhi_cntrl->mhi_dev->dev;
+ __le64 val;
+ int ret;
+
+ ring->mhi_cntrl = mhi_cntrl;
+ ring->ring_ctx = ctx;
+ ring->ring_size = mhi_ep_ring_num_elems(ring);
+ memcpy_fromio(&val, (void __iomem *) &ring->ring_ctx->generic.rbase, sizeof(u64));
+ ring->rbase = le64_to_cpu(val);
+
+ if (ring->type == RING_TYPE_CH)
+ ring->er_index = le32_to_cpu(ring->ring_ctx->ch.erindex);
+
+ if (ring->type == RING_TYPE_ER)
+ ring->irq_vector = le32_to_cpu(ring->ring_ctx->ev.msivec);
+
+ /* During ring init, both rp and wp are equal */
+ memcpy_fromio(&val, (void __iomem *) &ring->ring_ctx->generic.rp, sizeof(u64));
+ ring->rd_offset = mhi_ep_ring_addr2offset(ring, le64_to_cpu(val));
+ ring->wr_offset = mhi_ep_ring_addr2offset(ring, le64_to_cpu(val));
+
+ /* Allocate ring cache memory for holding the copy of host ring */
+ ring->ring_cache = kcalloc(ring->ring_size, sizeof(struct mhi_ring_element), GFP_KERNEL);
+ if (!ring->ring_cache)
+ return -ENOMEM;
+
+ memcpy_fromio(&val, (void __iomem *) &ring->ring_ctx->generic.wp, sizeof(u64));
+ ret = mhi_ep_cache_ring(ring, le64_to_cpu(val));
+ if (ret) {
+ dev_err(dev, "Failed to cache ring\n");
+ kfree(ring->ring_cache);
+ return ret;
+ }
+
+ ring->started = true;
+
+ return 0;
+}
+
+void mhi_ep_ring_reset(struct mhi_ep_cntrl *mhi_cntrl, struct mhi_ep_ring *ring)
+{
+ ring->started = false;
+ kfree(ring->ring_cache);
+ ring->ring_cache = NULL;
+}
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