* 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
#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;
return pcc_chan;
}
-/**
- * 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
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);
}
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);
static struct mbox_chan_ops pcc_chan_ops = {
.send_data = pcc_send_data,
- .last_tx_done = pcc_tx_done,
};
/**
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");
projects / firefly-linux-kernel-4.4.55.git / blobdiff