From: Carsten Haitzler <carsten.haitzler@xxxxxxx> When setting up a readback connector that writes data back to memory rather than to an actual output device (HDMI etc.), rounding was set to round. As the DPU uses a higher internal number of bits when generating a color value, this round-down back to 8bit ended up with everything being off-by one. e.g. #fefefe became #ffffff. This sets rounding to "round-down" so things end up correct by turning on the LW_TRC round down flag. Signed-off-by: Carsten Haitzler <carsten.haitzler@xxxxxxx> --- drivers/gpu/drm/arm/display/komeda/d71/d71_component.c | 7 ++++++- drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h | 1 + 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c index 8a02ade369db..e97acc5519d1 100644 --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c @@ -468,7 +468,12 @@ static void d71_wb_layer_update(struct komeda_component *c, struct komeda_layer_state *st = to_layer_st(state); struct drm_connector_state *conn_st = state->wb_conn->state; struct komeda_fb *kfb = to_kfb(conn_st->writeback_job->fb); - u32 ctrl = L_EN | LW_OFM, mask = L_EN | LW_OFM | LW_TBU_EN; + /* LW_TRC sets rounding to truncate not round which is needed for + * the output of writeback to match the input in the most common + * use cases like RGB888 -> RGB888, so set this bit by default + */ + u32 ctrl = LW_TRC | L_EN | LW_OFM; + u32 mask = LW_TRC | L_EN | LW_OFM | LW_TBU_EN; u32 __iomem *reg = c->reg; d71_layer_update_fb(c, kfb, st->addr); diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h index e80172a0b320..a8036689d721 100644 --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h @@ -321,6 +321,7 @@ #define LAYER_WR_FORMAT 0x0D8 /* Layer_WR control bits */ +#define LW_TRC BIT(1) #define LW_OFM BIT(4) #define LW_LALPHA(x) (((x) & 0xFF) << 8) #define LW_A_WCACHE(x) (((x) & 0xF) << 28) -- 2.30.0 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
