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Date: Mon, 28 Feb 2022 10:27:56 -0600
From: Alex Elder <elder@...aro.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
mhi@...ts.linux.dev
Cc: quic_hemantk@...cinc.com, quic_bbhatt@...cinc.com,
quic_jhugo@...cinc.com, vinod.koul@...aro.org,
bjorn.andersson@...aro.org, dmitry.baryshkov@...aro.org,
quic_vbadigan@...cinc.com, quic_cang@...cinc.com,
quic_skananth@...cinc.com, linux-arm-msm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 14/27] bus: mhi: ep: Add support for ring management
On 2/28/22 6:43 AM, Manivannan Sadhasivam wrote:
> Add support for managing the MHI ring. The MHI ring is a circular queue
> of data structures used to pass the information between host and the
> endpoint.
>
> MHI support 3 types of rings:
>
> 1. Transfer ring
> 2. Event ring
> 3. Command ring
>
> All rings reside inside the host memory and the MHI EP device maps it to
> the device memory using blocks like PCIe iATU. The mapping is handled in
> the MHI EP controller driver itself.
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Looks good.
Reviewed-by: Alex Elder <elder@...aro.org>
> ---
> drivers/bus/mhi/ep/Makefile | 2 +-
> drivers/bus/mhi/ep/internal.h | 18 ++++
> drivers/bus/mhi/ep/ring.c | 197 ++++++++++++++++++++++++++++++++++
> 3 files changed, 216 insertions(+), 1 deletion(-)
> create mode 100644 drivers/bus/mhi/ep/ring.c
>
> diff --git a/drivers/bus/mhi/ep/Makefile b/drivers/bus/mhi/ep/Makefile
> index a1555ae287ad..7ba0e04801eb 100644
> --- a/drivers/bus/mhi/ep/Makefile
> +++ b/drivers/bus/mhi/ep/Makefile
> @@ -1,2 +1,2 @@
> obj-$(CONFIG_MHI_BUS_EP) += mhi_ep.o
> -mhi_ep-y := main.o mmio.o
> +mhi_ep-y := main.o mmio.o ring.o
> diff --git a/drivers/bus/mhi/ep/internal.h b/drivers/bus/mhi/ep/internal.h
> index 139e939fcf57..b3b8770f2f4e 100644
> --- a/drivers/bus/mhi/ep/internal.h
> +++ b/drivers/bus/mhi/ep/internal.h
> @@ -114,6 +114,11 @@ union mhi_ep_ring_ctx {
> struct mhi_generic_ctx generic;
> };
>
> +struct mhi_ep_ring_item {
> + struct list_head node;
> + struct mhi_ep_ring *ring;
> +};
> +
> struct mhi_ep_ring {
> struct mhi_ep_cntrl *mhi_cntrl;
> union mhi_ep_ring_ctx *ring_ctx;
> @@ -126,6 +131,9 @@ struct mhi_ep_ring {
> u32 db_offset_h;
> u32 db_offset_l;
> u32 ch_id;
> + u32 er_index;
> + u32 irq_vector;
> + bool started;
> };
>
> struct mhi_ep_cmd {
> @@ -151,6 +159,16 @@ struct mhi_ep_chan {
> bool skip_td;
> };
>
> +/* MHI Ring related functions */
> +void mhi_ep_ring_init(struct mhi_ep_ring *ring, enum mhi_ep_ring_type type, u32 id);
> +void mhi_ep_ring_reset(struct mhi_ep_cntrl *mhi_cntrl, struct mhi_ep_ring *ring);
> +int mhi_ep_ring_start(struct mhi_ep_cntrl *mhi_cntrl, struct mhi_ep_ring *ring,
> + union mhi_ep_ring_ctx *ctx);
> +size_t mhi_ep_ring_addr2offset(struct mhi_ep_ring *ring, u64 ptr);
> +int mhi_ep_ring_add_element(struct mhi_ep_ring *ring, struct mhi_ring_element *element);
> +void mhi_ep_ring_inc_index(struct mhi_ep_ring *ring);
> +int mhi_ep_update_wr_offset(struct mhi_ep_ring *ring);
> +
> /* MMIO related functions */
> u32 mhi_ep_mmio_read(struct mhi_ep_cntrl *mhi_cntrl, u32 offset);
> void mhi_ep_mmio_write(struct mhi_ep_cntrl *mhi_cntrl, u32 offset, u32 val);
> diff --git a/drivers/bus/mhi/ep/ring.c b/drivers/bus/mhi/ep/ring.c
> new file mode 100644
> index 000000000000..1029eed2cc28
> --- /dev/null
> +++ b/drivers/bus/mhi/ep/ring.c
> @@ -0,0 +1,197 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2022 Linaro Ltd.
> + * Author: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.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)
> +{
> + return le64_to_cpu(ring->ring_ctx->generic.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;
> + 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 */
> + ring->ring_ctx->generic.rp = cpu_to_le64((ring->rd_offset * sizeof(*el)) + ring->rbase);
> +
> + 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;
> + int ret;
> +
> + ring->mhi_cntrl = mhi_cntrl;
> + ring->ring_ctx = ctx;
> + ring->ring_size = mhi_ep_ring_num_elems(ring);
> + ring->rbase = le64_to_cpu(ring->ring_ctx->generic.rbase);
> +
> + 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 */
> + ring->rd_offset = mhi_ep_ring_addr2offset(ring, le64_to_cpu(ring->ring_ctx->generic.rp));
> + ring->wr_offset = mhi_ep_ring_addr2offset(ring, le64_to_cpu(ring->ring_ctx->generic.rp));
> +
> + /* 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;
> +
> + ret = mhi_ep_cache_ring(ring, le64_to_cpu(ring->ring_ctx->generic.wp));
> + 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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