drivers/acpi/acpi_pcc.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Author: Sudeep Holla <sudeep.holla@arm.com>
   4  * Copyright 2021 Arm Limited
   5  *
   6  * The PCC Address Space also referred as PCC Operation Region pertains to the
   7  * region of PCC subspace that succeeds the PCC signature. The PCC Operation
   8  * Region works in conjunction with the PCC Table(Platform Communications
   9  * Channel Table). PCC subspaces that are marked for use as PCC Operation
  10  * Regions must not be used as PCC subspaces for the standard ACPI features
  11  * such as CPPC, RASF, PDTT and MPST. These standard features must always use
  12  * the PCC Table instead.
  13  *
  14  * This driver sets up the PCC Address Space and installs an handler to enable
  15  * handling of PCC OpRegion in the firmware.
  16  *
  17  */
  18 #include <linux/kernel.h>
  19 #include <linux/acpi.h>
  20 #include <linux/completion.h>
  21 #include <linux/idr.h>
  22 #include <linux/io.h>
  23
  24 #include <acpi/pcc.h>
  25
  26 /*
  27  * Arbitrary retries in case the remote processor is slow to respond
  28  * to PCC commands
  29  */
  30 #define PCC_CMD_WAIT_RETRIES_NUM        500ULL
  31
  32 struct pcc_data {
  33         struct pcc_mbox_chan *pcc_chan;
  34         void __iomem *pcc_comm_addr;
  35         struct completion done;
  36         struct mbox_client cl;
  37         struct acpi_pcc_info ctx;
  38 };
  39
  40 static struct acpi_pcc_info pcc_ctx;
  41
  42 static void pcc_rx_callback(struct mbox_client *cl, void *m)
  43 {
  44         struct pcc_data *data = container_of(cl, struct pcc_data, cl);
  45
  46         complete(&data->done);
  47 }
  48
  49 static acpi_status
  50 acpi_pcc_address_space_setup(acpi_handle region_handle, u32 function,
  51                              void *handler_context,  void **region_context)
  52 {
  53         struct pcc_data *data;
  54         struct acpi_pcc_info *ctx = handler_context;
  55         struct pcc_mbox_chan *pcc_chan;
  56
  57         data = kzalloc(sizeof(*data), GFP_KERNEL);
  58         if (!data)
  59                 return AE_NO_MEMORY;
  60
  61         data->cl.rx_callback = pcc_rx_callback;
  62         data->cl.knows_txdone = true;
  63         data->ctx.length = ctx->length;
  64         data->ctx.subspace_id = ctx->subspace_id;
  65         data->ctx.internal_buffer = ctx->internal_buffer;
  66
  67         init_completion(&data->done);
  68         data->pcc_chan = pcc_mbox_request_channel(&data->cl, ctx->subspace_id);
  69         if (IS_ERR(data->pcc_chan)) {
  70                 pr_err("Failed to find PCC channel for subspace %d\n",
  71                        ctx->subspace_id);
  72                 kfree(data);
  73                 return AE_NOT_FOUND;
  74         }
  75
  76         pcc_chan = data->pcc_chan;
  77         data->pcc_comm_addr = acpi_os_ioremap(pcc_chan->shmem_base_addr,
  78                                               pcc_chan->shmem_size);
  79         if (!data->pcc_comm_addr) {
  80                 pr_err("Failed to ioremap PCC comm region mem for %d\n",
  81                        ctx->subspace_id);
  82                 pcc_mbox_free_channel(data->pcc_chan);
  83                 kfree(data);
  84                 return AE_NO_MEMORY;
  85         }
  86
  87         *region_context = data;
  88         return AE_OK;
  89 }
  90
  91 static acpi_status
  92 acpi_pcc_address_space_handler(u32 function, acpi_physical_address addr,
  93                                u32 bits, acpi_integer *value,
  94                                void *handler_context, void *region_context)
  95 {
  96         int ret;
  97         struct pcc_data *data = region_context;
  98         u64 usecs_lat;
  99
 100         reinit_completion(&data->done);
 101
 102         /* Write to Shared Memory */
 103         memcpy_toio(data->pcc_comm_addr, (void *)value, data->ctx.length);
 104
 105         ret = mbox_send_message(data->pcc_chan->mchan, NULL);
 106         if (ret < 0)
 107                 return AE_ERROR;
 108
 109         if (data->pcc_chan->mchan->mbox->txdone_irq) {
 110                 /*
 111                  * pcc_chan->latency is just a Nominal value. In reality the remote
 112                  * processor could be much slower to reply. So add an arbitrary
 113                  * amount of wait on top of Nominal.
 114                  */
 115                 usecs_lat = PCC_CMD_WAIT_RETRIES_NUM * data->pcc_chan->latency;
 116                 ret = wait_for_completion_timeout(&data->done,
 117                                                   usecs_to_jiffies(usecs_lat));
 118                 if (ret == 0) {
 119                         pr_err("PCC command executed timeout!\n");
 120                         return AE_TIME;
 121                 }
 122         }
 123
 124         mbox_chan_txdone(data->pcc_chan->mchan, ret);
 125
 126         memcpy_fromio(value, data->pcc_comm_addr, data->ctx.length);
 127
 128         return AE_OK;
 129 }
 130
 131 void __init acpi_init_pcc(void)
 132 {
 133         acpi_status status;
 134
 135         status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
 136                                                     ACPI_ADR_SPACE_PLATFORM_COMM,
 137                                                     &acpi_pcc_address_space_handler,
 138                                                     &acpi_pcc_address_space_setup,
 139                                                     &pcc_ctx);
 140         if (ACPI_FAILURE(status))
 141                 pr_alert("OperationRegion handler could not be installed\n");
 142 }