[PATCH] soundwire: qcom: add SCP address paging support

[Jorijn van der Graaf]

The Qualcomm controller driver ignores the paging fields of struct
sdw_msg. For a paged access (register address >= 0x8000 on a
paging-capable peripheral, e.g. the SDCA control space at
0x40000000+) the core sets BIT(15) in the wire address and splits the
upper bits into addr_page1/addr_page2, but since the controller never
programmed the SCP_AddrPage registers the peripheral resolved every
such command against their reset value: reads and writes were
silently redirected to addr[14:0] in page 0.

Write the two SCP_AddrPage registers through the command FIFO before
the transfer, as cadence_master.c (cdns_program_scp_addr) and
amd_manager.c (amd_program_scp_addr) do. Like those controllers the
pages are programmed on every paged message rather than cached per
device; a cache can be a follow-up if the two extra FIFO commands
ever matter.

No peripheral on a Qualcomm bus sets prop.paging_support in mainline
today; the first user is the WCD9378 codec, whose driver is being
upstreamed separately - its entire register map, the
wcd937x-compatible analog core included, lives in the SDCA address
space.

Verified on the Fairphone 6 (SM7635): WCD9378 SDCA registers read
back their documented reset defaults and audio capture through the
codec works end-to-end; without this change every paged access landed
in page 0.

Assisted-by: Claude:claude-fable-5
Signed-off-by: Jorijn van der Graaf <jorijnvdgraaf@xxxxxxxxxxxxx>
---
 drivers/soundwire/qcom.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
index 603f228f46b5..3562802f4204 100644
--- a/drivers/soundwire/qcom.c
+++ b/drivers/soundwire/qcom.c
@@ -975,6 +975,20 @@ static enum sdw_command_response qcom_swrm_xfer_msg(struct sdw_bus *bus,
 	struct qcom_swrm_ctrl *ctrl = to_qcom_sdw(bus);
 	int ret, i, len;
 
+	if (msg->page) {
+		ret = qcom_swrm_cmd_fifo_wr_cmd(ctrl, msg->addr_page1,
+						msg->dev_num,
+						SDW_SCP_ADDRPAGE1);
+		if (ret)
+			return ret;
+
+		ret = qcom_swrm_cmd_fifo_wr_cmd(ctrl, msg->addr_page2,
+						msg->dev_num,
+						SDW_SCP_ADDRPAGE2);
+		if (ret)
+			return ret;
+	}
+
 	if (msg->flags == SDW_MSG_FLAG_READ) {
 		for (i = 0; i < msg->len;) {
 			len = min(msg->len - i, QCOM_SWRM_MAX_RD_LEN);
-- 
2.55.0