Hi,
On Tue, Dec 08, 2020 at 02:28:32PM +0200, Tomi Valkeinen wrote:
> The OMAP DSI command mode panel driver used to send page & column
> address before each frame update, and this code was moved into the DSI
> host driver when converting it to the DRM bridge model.
>
> However, it's not really required to send the page & column address
> before each frame. It's also something that doesn't really belong to the
> DSI host driver, so we should drop the code.
>
> That said, frame updates break if we don't send _something_ between the
> frames. A NOP command does the trick.
>
> It is not clear if this behavior is as expected from a DSI command mode
> frame transfer, or is it a feature/issue with OMAP DSI driver, or a
> feature/issue in the command mode panel used.
>
> Most likely this is related to the following from the DSI spec:
>
> "To enable PHY synchronization the host processor should periodically
> end HS transmission and drive the Data Lanes to the LP state. This
> transition should take place at least once per frame."
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
Reviewed-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
-- Sebastian
> drivers/gpu/drm/omapdrm/dss/dsi.c | 46 ++++++++++++-------------------
> 1 file changed, 17 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/gpu/drm/omapdrm/dss/dsi.c b/drivers/gpu/drm/omapdrm/dss/dsi.c
> index 7fee9cf8782d..c6e044f8bece 100644
> --- a/drivers/gpu/drm/omapdrm/dss/dsi.c
> +++ b/drivers/gpu/drm/omapdrm/dss/dsi.c
> @@ -3884,35 +3884,19 @@ static int _dsi_update(struct dsi_data *dsi)
> return 0;
> }
>
> -static int _dsi_update_window(struct dsi_data *dsi, int channel,
> - int x, int y, int w, int h)
> -{
> - int x1 = x, x2 = (x + w - 1);
> - int y1 = y, y2 = (y + h - 1);
> - u8 payloadX[5] = { MIPI_DCS_SET_COLUMN_ADDRESS,
> - x1 >> 8, x1 & 0xff, x2 >> 8, x2 & 0xff };
> - u8 payloadY[5] = { MIPI_DCS_SET_PAGE_ADDRESS,
> - y1 >> 8, y1 & 0xff, y2 >> 8, y2 & 0xff };
> - struct mipi_dsi_msg msgX = { 0 }, msgY = { 0 };
> - int ret;
> +static int _dsi_send_nop(struct dsi_data *dsi, int channel)
> +{
> + const u8 payload[] = { MIPI_DCS_NOP };
> + const struct mipi_dsi_msg msg = {
> + .channel = channel,
> + .type = MIPI_DSI_DCS_SHORT_WRITE,
> + .tx_len = 1,
> + .tx_buf = payload,
> + };
>
> WARN_ON(!dsi_bus_is_locked(dsi));
>
> - msgX.type = MIPI_DSI_DCS_LONG_WRITE;
> - msgX.channel = channel;
> - msgX.tx_buf = payloadX;
> - msgX.tx_len = sizeof(payloadX);
> -
> - msgY.type = MIPI_DSI_DCS_LONG_WRITE;
> - msgY.channel = channel;
> - msgY.tx_buf = payloadY;
> - msgY.tx_len = sizeof(payloadY);
> -
> - ret = _omap_dsi_host_transfer(dsi, &msgX);
> - if (ret != 0)
> - return ret;
> -
> - return _omap_dsi_host_transfer(dsi, &msgY);
> + return _omap_dsi_host_transfer(dsi, &msg);
> }
>
> static int dsi_update_channel(struct omap_dss_device *dssdev, int channel)
> @@ -3944,10 +3928,14 @@ static int dsi_update_channel(struct omap_dss_device *dssdev, int channel)
>
> dsi_set_ulps_auto(dsi, false);
>
> - r = _dsi_update_window(dsi, channel, 0, 0, dsi->vm.hactive,
> - dsi->vm.vactive);
> + /*
> + * Send NOP between the frames. If we don't send something here, the
> + * updates stop working. This is probably related to DSI spec stating
> + * that the DSI host should transition to LP at least once per frame.
> + */
> + r = _dsi_send_nop(dsi, channel);
> if (r < 0) {
> - DSSWARN("window update error: %d\n", r);
> + DSSWARN("failed to send nop between frames: %d\n", r);
> goto err;
> }
>
> --
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>
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