Revert "mailbox/pcc: support mailbox management of the shared buffer"

[ Upstream commit f82c3e62b6b8c31d8c56415bf38658f306fda4cb ]

This reverts commit 5378bdf6a611a32500fccf13d14156f219bb0c85.

Commit 5378bdf6a611 ("mailbox/pcc: support mailbox management of the shared buffer")
attempted to introduce generic helpers for managing the PCC shared memory,
but it largely duplicates functionality already provided by the mailbox
core and leaves gaps:

1. TX preparation: The mailbox framework already supports this via
  ->tx_prepare callback for mailbox clients. The patch adds
  pcc_write_to_buffer() and expects clients to toggle pchan->chan.manage_writes,
  but no drivers set manage_writes, so pcc_write_to_buffer() has no users.

2. RX handling: Data reception is already delivered through
   mbox_chan_received_data() and client ->rx_callback. The patch adds an
   optional pchan->chan.rx_alloc, which again has no users and duplicates
   the existing path.

3. Completion handling: While adding last_tx_done is directionally useful,
   the implementation only covers Type 3/4 and fails to handle the absence
   of a command_complete register, so it is incomplete for other types.

Given the duplication and incomplete coverage, revert this change. Any new
requirements should be addressed in focused follow-ups rather than bundling
multiple behavioral changes together.

Fixes: 5378bdf6a611 ("mailbox/pcc: support mailbox management of the shared buffer")
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

1 files changed, 0 insertions, 29 deletions

diff --git a/include/acpi/pcc.h b/include/acpi/pcc.h
index 9af3b502f839..840bfc95bae3 100644
--- a/include/acpi/pcc.h
+++ b/include/acpi/pcc.h
@@ -17,35 +17,6 @@ struct pcc_mbox_chan {
 	u32 latency;
 	u32 max_access_rate;
 	u16 min_turnaround_time;
-
-	/* Set to true to indicate that the mailbox should manage
-	 * writing the dat to the shared buffer. This differs from
-	 * the case where the drivesr are writing to the buffer and
-	 * using send_data only to  ring the doorbell.  If this flag
-	 * is set, then the void * data parameter of send_data must
-	 * point to a kernel-memory buffer formatted in accordance with
-	 * the PCC specification.
-	 *
-	 * The active buffer management will include reading the
-	 * notify_on_completion flag, and will then
-	 * call mbox_chan_txdone when the acknowledgment interrupt is
-	 * received.
-	 */
-	bool manage_writes;
-
-	/* Optional callback that allows the driver
-	 * to allocate the memory used for receiving
-	 * messages.  The return value is the location
-	 * inside the buffer where the mailbox should write the data.
-	 */
-	void *(*rx_alloc)(struct mbox_client *cl,  int size);
-};
-
-struct pcc_header {
-	u32 signature;
-	u32 flags;
-	u32 length;
-	u32 command;
 };
 
 /* Generic Communications Channel Shared Memory Region */