[PATCH 08/11] soundwire: generic_bandwidth_allocation: fix hwidth for skipped block offset

[Vijendar Mukunda <Vijendar.Mukunda@amd.com>]

The hwidth computation in sdw_compute_group_params() used bare
payload_bw when calculating the horizontal columns required for a
stream group. The generic transport programming starts payload block
offsets from block_offset 1, so offset 0 is skipped. Without
accounting for that skipped offset, some frame configurations can
program an hstart/hstop payload window that is too narrow.

Introduce sdw_compute_hwidth() which adds 1 to payload_bw before
the ceiling division to account for the skipped slot. Also skip
groups with zero payload_bw before calling sdw_compute_hwidth(),
and skip groups with a resulting hwidth of 0 to avoid emitting
an invalid hstart/hstop range.

Fixes: 9026118f20e2 ("soundwire: Add generic bandwidth allocation algorithm")
Signed-off-by: Poojitha N <Poojitha.N@amd.com>
Signed-off-by: Vijendar Mukunda <Vijendar.Mukunda@amd.com>
---
 .../soundwire/generic_bandwidth_allocation.c    | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/soundwire/generic_bandwidth_allocation.c b/drivers/soundwire/generic_bandwidth_allocation.c
index 30a495abe19e..1dd3b2e5420c 100644
--- a/drivers/soundwire/generic_bandwidth_allocation.c
+++ b/drivers/soundwire/generic_bandwidth_allocation.c
@@ -15,6 +15,12 @@
 
 #define SDW_STRM_RATE_GROUPING		1
 
+static int sdw_compute_hwidth(int col, int payload_bw, int full_bw)
+{
+	/* Account for the initial skipped payload bit at block offset 0. */
+	return (col * (payload_bw + 1) + full_bw - 1) / full_bw;
+}
+
 struct sdw_group_params {
 	unsigned int rate;
 	unsigned int lane;
@@ -203,6 +209,9 @@ static void _sdw_compute_port_params(struct sdw_bus *bus,
 		for (i = 0; i < count; i++) {
 			if (params[i].lane != l)
 				continue;
+			/* Skip inactive groups to avoid an invalid hstart/hstop range. */
+			if (!params[i].hwidth)
+				continue;
 			port_bo = 1;
 
 			list_for_each_entry(m_rt, &bus->m_rt_list, bus_node) {
@@ -274,9 +283,13 @@ static int sdw_compute_group_params(struct sdw_bus *bus,
 		for (i = 0; i < group->count; i++) {
 			if (params[i].lane != l)
 				continue;
+			/* Inactive groups must not enter the hwidth calculation. */
+			if (!params[i].payload_bw)
+				continue;
 
-			params[i].hwidth = (sel_col * params[i].payload_bw +
-					    params[i].full_bw - 1) / params[i].full_bw;
+			params[i].hwidth =
+				sdw_compute_hwidth(sel_col, params[i].payload_bw,
+						   params[i].full_bw);
 
 			column_needed += params[i].hwidth;
 			/* There is no control column for lane 1 and above */
-- 
2.53.0