drivers/firmware/arm_scmi/shmem.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * For transport using shared mem structure.
   4  *
   5  * Copyright (C) 2019 ARM Ltd.
   6  */
   7
   8 #include <linux/io.h>
   9 #include <linux/processor.h>
  10 #include <linux/types.h>
  11
  12 #include "common.h"
  13
  14 /*
  15  * SCMI specification requires all parameters, message headers, return
  16  * arguments or any protocol data to be expressed in little endian
  17  * format only.
  18  */
  19 struct scmi_shared_mem {
  20         __le32 reserved;
  21         __le32 channel_status;
  22 #define SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR      BIT(1)
  23 #define SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE       BIT(0)
  24         __le32 reserved1[2];
  25         __le32 flags;
  26 #define SCMI_SHMEM_FLAG_INTR_ENABLED    BIT(0)
  27         __le32 length;
  28         __le32 msg_header;
  29         u8 msg_payload[];
  30 };
  31
  32 void shmem_tx_prepare(struct scmi_shared_mem __iomem *shmem,
  33                       struct scmi_xfer *xfer)
  34 {
  35         /*
  36          * Ideally channel must be free by now unless OS timeout last
  37          * request and platform continued to process the same, wait
  38          * until it releases the shared memory, otherwise we may endup
  39          * overwriting its response with new message payload or vice-versa
  40          */
  41         spin_until_cond(ioread32(&shmem->channel_status) &
  42                         SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
  43         /* Mark channel busy + clear error */
  44         iowrite32(0x0, &shmem->channel_status);
  45         iowrite32(xfer->hdr.poll_completion ? 0 : SCMI_SHMEM_FLAG_INTR_ENABLED,
  46                   &shmem->flags);
  47         iowrite32(sizeof(shmem->msg_header) + xfer->tx.len, &shmem->length);
  48         iowrite32(pack_scmi_header(&xfer->hdr), &shmem->msg_header);
  49         if (xfer->tx.buf)
  50                 memcpy_toio(shmem->msg_payload, xfer->tx.buf, xfer->tx.len);
  51 }
  52
  53 u32 shmem_read_header(struct scmi_shared_mem __iomem *shmem)
  54 {
  55         return ioread32(&shmem->msg_header);
  56 }
  57
  58 void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem,
  59                           struct scmi_xfer *xfer)
  60 {
  61         xfer->hdr.status = ioread32(shmem->msg_payload);
  62         /* Skip the length of header and status in shmem area i.e 8 bytes */
  63         xfer->rx.len = min_t(size_t, xfer->rx.len,
  64                              ioread32(&shmem->length) - 8);
  65
  66         /* Take a copy to the rx buffer.. */
  67         memcpy_fromio(xfer->rx.buf, shmem->msg_payload + 4, xfer->rx.len);
  68 }
  69
  70 void shmem_fetch_notification(struct scmi_shared_mem __iomem *shmem,
  71                               size_t max_len, struct scmi_xfer *xfer)
  72 {
  73         /* Skip only the length of header in shmem area i.e 4 bytes */
  74         xfer->rx.len = min_t(size_t, max_len, ioread32(&shmem->length) - 4);
  75
  76         /* Take a copy to the rx buffer.. */
  77         memcpy_fromio(xfer->rx.buf, shmem->msg_payload, xfer->rx.len);
  78 }
  79
  80 void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem)
  81 {
  82         iowrite32(SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE, &shmem->channel_status);
  83 }
  84
  85 bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
  86                      struct scmi_xfer *xfer)
  87 {
  88         u16 xfer_id;
  89
  90         xfer_id = MSG_XTRACT_TOKEN(ioread32(&shmem->msg_header));
  91
  92         if (xfer->hdr.seq != xfer_id)
  93                 return false;
  94
  95         return ioread32(&shmem->channel_status) &
  96                 (SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR |
  97                  SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
  98 }