Commit c8a0d6b2 authored by Richard Fitzgerald's avatar Richard Fitzgerald Committed by Vinod Koul
Browse files

soundwire: bus: Don't zero page registers after every transaction 



Zeroing the page registers at the end of every paged transaction is just
overhead (40% overhead on a 1-register access, 25% on a 4-register
transaction). According to the spec a peripheral that supports paging
should only use the values in the page registers if the address is paged
(address bit 15 set). The core SoundWire code always writes the page
registers at the start of a paged transaction so there will never be a
transaction that uses the stale values from a previous paged transaction.

For peripherals that need large amounts of data to be transferred, for
example firmware or filter coefficients, the overhead of page register
zeroing can become quite significant.

Signed-off-by: default avatarRichard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: default avatarPierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20230123164949.245898-2-rf@opensource.cirrus.com


Signed-off-by: default avatarVinod Koul <vkoul@kernel.org>
parent 3dca1f89

drivers/soundwire/bus.c

+0 −23
Original line number Diff line number Diff line
@@ -247,23 +247,6 @@ static inline int do_transfer_defer(struct sdw_bus *bus, 
	return ret;

}



static int sdw_reset_page(struct sdw_bus *bus, u16 dev_num)

{

	int retry = bus->prop.err_threshold;

	enum sdw_command_response resp;

	int ret = 0, i;



	for (i = 0; i <= retry; i++) {

		resp = bus->ops->reset_page_addr(bus, dev_num);

		ret = find_response_code(resp);

		/* if cmd is ok or ignored return */

		if (ret == 0 || ret == -ENODATA)

			return ret;

	}



	return ret;

}



static int sdw_transfer_unlocked(struct sdw_bus *bus, struct sdw_msg *msg)

{

	int ret;
@@ -275,9 +258,6 @@ static int sdw_transfer_unlocked(struct sdw_bus *bus, struct sdw_msg *msg) 
			(msg->flags & SDW_MSG_FLAG_WRITE) ? "write" : "read",

			msg->addr, msg->len);



	if (msg->page)

		sdw_reset_page(bus, msg->dev_num);



	return ret;

}
@@ -352,9 +332,6 @@ int sdw_transfer_defer(struct sdw_bus *bus, struct sdw_msg *msg, 
		dev_err(bus->dev, "Defer trf on Slave %d failed:%d\n",

			msg->dev_num, ret);



	if (msg->page)

		sdw_reset_page(bus, msg->dev_num);



	return ret;

}