1 files changed, 37 insertions, 85 deletions

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index 977c814cdf6f..7e91d68a3ac3 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -20,10 +20,35 @@
  *  shared memory regions as defined in the PCC table entries. The PCC
  *  specification supports a Doorbell mechanism for the PCC clients
  *  to notify the platform about new data. This Doorbell information
- *  is also specified in each PCC table entry. See pcc_send_data()
- *  and pcc_tx_done() for basic mode of operation.
+ *  is also specified in each PCC table entry.
  *
- *  For more details about PCC, please see the ACPI specification from
+ *  Typical high level flow of operation is:
+ *
+ *  PCC Reads:
+ *  * Client tries to acquire a channel lock.
+ *  * After it is acquired it writes READ cmd in communication region cmd
+ *              address.
+ *  * Client issues mbox_send_message() which rings the PCC doorbell
+ *              for its PCC channel.
+ *  * If command completes, then client has control over channel and
+ *              it can proceed with its reads.
+ *  * Client releases lock.
+ *
+ *  PCC Writes:
+ *  * Client tries to acquire channel lock.
+ *  * Client writes to its communication region after it acquires a
+ *              channel lock.
+ *  * Client writes WRITE cmd in communication region cmd address.
+ *  * Client issues mbox_send_message() which rings the PCC doorbell
+ *              for its PCC channel.
+ *  * If command completes, then writes have succeded and it can release
+ *              the channel lock.
+ *
+ *  There is a Nominal latency defined for each channel which indicates
+ *  how long to wait until a command completes. If command is not complete
+ *  the client needs to retry or assume failure.
+ *
+ *      For more details about PCC, please see the ACPI specification from
  *  http://www.uefi.org/ACPIv5.1 Section 14.
  *
  *  This file implements PCC as a Mailbox controller and allows for PCC
@@ -42,8 +67,6 @@
 #include "mailbox.h"
 
 #define MAX_PCC_SUBSPACES       256
-#define PCCS_SS_SIG_MAGIC       0x50434300
-#define PCC_CMD_COMPLETE        0x1
 
 static struct mbox_chan *pcc_mbox_channels;
 
@@ -71,23 +94,6 @@ static struct mbox_chan *get_pcc_channel(int id)
 }
 
 /**
- * get_subspace_id - Given a Mailbox channel, find out the
- *              PCC subspace id.
- * @chan: Pointer to Mailbox Channel from which we want
- *              the index.
- * Return: Errno if not found, else positive index number.
- */
-static int get_subspace_id(struct mbox_chan *chan)
-{
-        unsigned int id = chan - pcc_mbox_channels;
-
-        if (id < 0 || id > pcc_mbox_ctrl.num_chans)
-                return -ENOENT;
-
-        return id;
-}
-
-/**
  * pcc_mbox_request_channel - PCC clients call this function to
  *              request a pointer to their PCC subspace, from which they
  *              can get the details of communicating with the remote.
@@ -117,7 +123,7 @@ struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
         chan = get_pcc_channel(subspace_id);
 
         if (!chan || chan->cl) {
-                dev_err(dev, "%s: PCC mailbox not free\n", __func__);
+                dev_err(dev, "Channel not found for idx: %d\n", subspace_id);
                 return ERR_PTR(-EBUSY);
         }
 
@@ -161,81 +167,30 @@ void pcc_mbox_free_channel(struct mbox_chan *chan)
 EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
 
 /**
- * pcc_tx_done - Callback from Mailbox controller code to
- *              check if PCC message transmission completed.
- * @chan: Pointer to Mailbox channel on which previous
- *              transmission occurred.
- *
- * Return: TRUE if succeeded.
- */
-static bool pcc_tx_done(struct mbox_chan *chan)
-{
-        struct acpi_pcct_hw_reduced *pcct_ss = chan->con_priv;
-        struct acpi_pcct_shared_memory *generic_comm_base =
-                (struct acpi_pcct_shared_memory *) pcct_ss->base_address;
-        u16 cmd_delay = pcct_ss->latency;
-        unsigned int retries = 0;
-
-        /* Try a few times while waiting for platform to consume */
-        while (!(readw_relaxed(&generic_comm_base->status)
-                    & PCC_CMD_COMPLETE)) {
-
-                if (retries++ < 5)
-                        udelay(cmd_delay);
-                else {
-                        /*
-                         * If the remote is dead, this will cause the Mbox
-                         * controller to timeout after mbox client.tx_tout
-                         * msecs.
-                         */
-                        pr_err("PCC platform did not respond.\n");
-                        return false;
-                }
-        }
-        return true;
-}
-
-/**
- * pcc_send_data - Called from Mailbox Controller code to finally
- *      transmit data over channel.
+ * pcc_send_data - Called from Mailbox Controller code. Used
+ *              here only to ring the channel doorbell. The PCC client
+ *              specific read/write is done in the client driver in
+ *              order to maintain atomicity over PCC channel once
+ *              OS has control over it. See above for flow of operations.
  * @chan: Pointer to Mailbox channel over which to send data.
- * @data: Actual data to be written over channel.
+ * @data: Client specific data written over channel. Used here
+ *              only for debug after PCC transaction completes.
  *
  * Return: Err if something failed else 0 for success.
  */
 static int pcc_send_data(struct mbox_chan *chan, void *data)
 {
         struct acpi_pcct_hw_reduced *pcct_ss = chan->con_priv;
-        struct acpi_pcct_shared_memory *generic_comm_base =
-                (struct acpi_pcct_shared_memory *) pcct_ss->base_address;
         struct acpi_generic_address doorbell;
         u64 doorbell_preserve;
         u64 doorbell_val;
         u64 doorbell_write;
-        u16 cmd = *(u16 *) data;
-        u16 ss_idx = -1;
-
-        ss_idx = get_subspace_id(chan);
-
-        if (ss_idx < 0) {
-                pr_err("Invalid Subspace ID from PCC client\n");
-                return -EINVAL;
-        }
 
         doorbell = pcct_ss->doorbell_register;
         doorbell_preserve = pcct_ss->preserve_mask;
         doorbell_write = pcct_ss->write_mask;
 
-        /* Write to the shared comm region. */
-        writew(cmd, &generic_comm_base->command);
-
-        /* Write Subspace MAGIC value so platform can identify destination. */
-        writel((PCCS_SS_SIG_MAGIC | ss_idx), &generic_comm_base->signature);
-
-        /* Flip CMD COMPLETE bit */
-        writew(0, &generic_comm_base->status);
-
-        /* Sync notification from OSPM to Platform. */
+        /* Sync notification from OS to Platform. */
         acpi_read(&doorbell_val, &doorbell);
         acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
                         &doorbell);
@@ -245,7 +200,6 @@ static int pcc_send_data(struct mbox_chan *chan, void *data)
 
 static struct mbox_chan_ops pcc_chan_ops = {
         .send_data = pcc_send_data,
-        .last_tx_done = pcc_tx_done,
 };
 
 /**
@@ -351,8 +305,6 @@ static int pcc_mbox_probe(struct platform_device *pdev)
 
         pcc_mbox_ctrl.chans = pcc_mbox_channels;
         pcc_mbox_ctrl.ops = &pcc_chan_ops;
-        pcc_mbox_ctrl.txdone_poll = true;
-        pcc_mbox_ctrl.txpoll_period = 10;
         pcc_mbox_ctrl.dev = &pdev->dev;
 
         pr_info("Registering PCC driver as Mailbox controller\n");