Re: [PATCH] drm: mediatek: mtk_dsi: Fix NO_EOT_PACKET settings/handling

From: Alexandre Mergnat
Date: Fri Jun 23 2023 - 07:29:55 EST




On 23/06/2023 11:47, AngeloGioacchino Del Regno wrote:
Il 23/05/23 12:42, AngeloGioacchino Del Regno ha scritto:
Due to the initial confusion about MIPI_DSI_MODE_EOT_PACKET, properly
renamed to MIPI_DSI_MODE_NO_EOT_PACKET, reflecting its actual meaning,
both the DSI_TXRX_CON register setting for bit (HSTX_)DIS_EOT and the
later calculation for horizontal sync-active (HSA), back (HBP) and
front (HFP) porches got incorrect due to the logic being inverted.

This means that a number of settings were wrong because....:
  - DSI_TXRX_CON register setting: bit (HSTX_)DIS_EOT should be
    set in order to disable the End of Transmission packet;
  - Horizontal Sync and Back/Front porches: The delta used to
    calculate all of HSA, HBP and HFP should account for the
    additional EOT packet.

Before this change...
  - Bit (HSTX_)DIS_EOT was being set when EOT packet was enabled;
  - For HSA/HBP/HFP delta... all three were wrong, as words were
    added when EOT disabled, instead of when EOT packet enabled!

Invert the logic around flag MIPI_DSI_MODE_NO_EOT_PACKET in the
MediaTek DSI driver to fix the aforementioned issues.

Fixes: 8b2b99fd7931 ("drm/mediatek: dsi: Fine tune the line time caused by EOTp")
Fixes: 2d52bfba09d1 ("drm/mediatek: add non-continuous clock mode and EOT packet control")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>

Gentle ping for an important fix.

Regards,
Angelo

---
  drivers/gpu/drm/mediatek/mtk_dsi.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index 7d5250351193..b0ab38e59db9 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -407,7 +407,7 @@ static void mtk_dsi_rxtx_control(struct mtk_dsi *dsi)
      if (dsi->mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS)
          tmp_reg |= HSTX_CKLP_EN;
-    if (!(dsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET))
+    if (dsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET)
          tmp_reg |= DIS_EOT;
      writel(tmp_reg, dsi->regs + DSI_TXRX_CTRL);
@@ -484,7 +484,7 @@ static void mtk_dsi_config_vdo_timing(struct mtk_dsi *dsi)
                timing->da_hs_zero + timing->da_hs_exit + 3;
      delta = dsi->mode_flags & MIPI_DSI_MODE_VIDEO_BURST ? 18 : 12;
-    delta += dsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET ? 2 : 0;
+    delta += dsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET ? 0 : 2;
      horizontal_frontporch_byte = vm->hfront_porch * dsi_tmp_buf_bpp;
      horizontal_front_back_byte = horizontal_frontporch_byte + horizontal_backporch_byte;



Sounds logic

Reviewed-by: Alexandre Mergnat <amergnat@xxxxxxxxxxxx>

--
Regards,
Alexandre