[PATCH 2/4] drm/msm/dsi: Fix compressed word count calculation

[Jessica Zhang]

Currently, word count is calculated using slice_count. This is incorrect
as downstream uses slice per packet, which is different from
slice_count.

Slice count represents the number of soft slices per interface, and its
value will not always match that of slice per packet. For example, it is
possible to have cases where there are multiple soft slices per interface
but the panel specifies only one slice per packet.

Thus, use the default value of one slice per packet and remove slice_count
from the word count calculation.

Fixes: bc6b6ff8135c ("drm/msm/dsi: Use DSC slice(s) packet size to compute word count")
Signed-off-by: Jessica Zhang <quic_jesszhan at quicinc.com>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 35c69dbe5f6f..b0d448ffb078 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -996,7 +996,14 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
 		if (!msm_host->dsc)
 			wc = hdisplay * dsi_get_bpp(msm_host->format) / 8 + 1;
 		else
-			wc = msm_host->dsc->slice_chunk_size * msm_host->dsc->slice_count + 1;
+			/*
+			 * When DSC is enabled, WC = slice_chunk_size * slice_per_packet + 1.
+			 * Currently, the driver only supports default value of slice_per_packet = 1
+			 *
+			 * TODO: Expand drm_panel struct to hold slice_per_packet info
+			 *       and adjust DSC math to account for slice_per_packet.
+			 */
+			wc = msm_host->dsc->slice_chunk_size + 1;
 
 		dsi_write(msm_host, REG_DSI_CMD_MDP_STREAM0_CTRL,
 			DSI_CMD_MDP_STREAM0_CTRL_WORD_COUNT(wc) |

-- 
2.40.1