Re: [PATCH v6 2/2] drm/bridge: Add NWL MIPI DSI host controller support

[kbuild test robot <lkp@intel.com>]

Hi "Guido,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[cannot apply to v5.3 next-20190920]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Guido-G-nther/drm-bridge-Add-NWL-MIPI-DSI-host-controller-support/20190923-005010

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

smatch warnings:
drivers/gpu/drm/bridge/nwl-dsi.c:272 nwl_dsi_config_dpi() warn: unsigned 'color_format' is never less than zero.

vim +/color_format +272 drivers/gpu/drm/bridge/nwl-dsi.c

   245	
   246	static int nwl_dsi_config_dpi(struct nwl_dsi *dsi)
   247	{
   248		u32 color_format, mode;
   249		bool burst_mode;
   250		int hfront_porch, hback_porch, vfront_porch, vback_porch;
   251		int hsync_len, vsync_len;
   252	
   253		hfront_porch = dsi->mode.hsync_start - dsi->mode.hdisplay;
   254		hsync_len = dsi->mode.hsync_end - dsi->mode.hsync_start;
   255		hback_porch = dsi->mode.htotal - dsi->mode.hsync_end;
   256	
   257		vfront_porch = dsi->mode.vsync_start - dsi->mode.vdisplay;
   258		vsync_len = dsi->mode.vsync_end - dsi->mode.vsync_start;
   259		vback_porch = dsi->mode.vtotal - dsi->mode.vsync_end;
   260	
   261		DRM_DEV_DEBUG_DRIVER(dsi->dev, "hfront_porch = %d\n", hfront_porch);
   262		DRM_DEV_DEBUG_DRIVER(dsi->dev, "hback_porch = %d\n", hback_porch);
   263		DRM_DEV_DEBUG_DRIVER(dsi->dev, "hsync_len = %d\n", hsync_len);
   264		DRM_DEV_DEBUG_DRIVER(dsi->dev, "hdisplay = %d\n", dsi->mode.hdisplay);
   265		DRM_DEV_DEBUG_DRIVER(dsi->dev, "vfront_porch = %d\n", vfront_porch);
   266		DRM_DEV_DEBUG_DRIVER(dsi->dev, "vback_porch = %d\n", vback_porch);
   267		DRM_DEV_DEBUG_DRIVER(dsi->dev, "vsync_len = %d\n", vsync_len);
   268		DRM_DEV_DEBUG_DRIVER(dsi->dev, "vactive = %d\n", dsi->mode.vdisplay);
   269		DRM_DEV_DEBUG_DRIVER(dsi->dev, "clock = %d kHz\n", dsi->mode.clock);
   270	
   271		color_format = nwl_dsi_get_dpi_pixel_format(dsi->format);
 > 272		if (color_format < 0) {
   273			DRM_DEV_ERROR(dsi->dev, "Invalid color format 0x%x\n",
   274				      dsi->format);
   275			return color_format;
   276		}
   277		DRM_DEV_DEBUG_DRIVER(dsi->dev, "pixel fmt = %d\n", dsi->format);
   278	
   279		nwl_dsi_write(dsi, NWL_DSI_INTERFACE_COLOR_CODING, NWL_DSI_DPI_24_BIT);
   280		nwl_dsi_write(dsi, NWL_DSI_PIXEL_FORMAT, color_format);
   281		/*
   282		 * Adjusting input polarity based on the video mode results in
   283		 * a black screen so always pick active low:
   284		 */
   285		nwl_dsi_write(dsi, NWL_DSI_VSYNC_POLARITY,
   286			      NWL_DSI_VSYNC_POLARITY_ACTIVE_LOW);
   287		nwl_dsi_write(dsi, NWL_DSI_HSYNC_POLARITY,
   288			      NWL_DSI_HSYNC_POLARITY_ACTIVE_LOW);
   289	
   290		burst_mode = (dsi->dsi_mode_flags & MIPI_DSI_MODE_VIDEO_BURST) &&
   291			     !(dsi->dsi_mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE);
   292	
   293		if (burst_mode) {
   294			nwl_dsi_write(dsi, NWL_DSI_VIDEO_MODE, NWL_DSI_VM_BURST_MODE);
   295			nwl_dsi_write(dsi, NWL_DSI_PIXEL_FIFO_SEND_LEVEL, 256);
   296		} else {
   297			mode = ((dsi->dsi_mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE) ?
   298					NWL_DSI_VM_BURST_MODE_WITH_SYNC_PULSES :
   299					NWL_DSI_VM_NON_BURST_MODE_WITH_SYNC_EVENTS);
   300			nwl_dsi_write(dsi, NWL_DSI_VIDEO_MODE, mode);
   301			nwl_dsi_write(dsi, NWL_DSI_PIXEL_FIFO_SEND_LEVEL,
   302				      dsi->mode.hdisplay);
   303		}
   304	
   305		nwl_dsi_write(dsi, NWL_DSI_HFP, hfront_porch);
   306		nwl_dsi_write(dsi, NWL_DSI_HBP, hback_porch);
   307		nwl_dsi_write(dsi, NWL_DSI_HSA, hsync_len);
   308	
   309		nwl_dsi_write(dsi, NWL_DSI_ENABLE_MULT_PKTS, 0x0);
   310		nwl_dsi_write(dsi, NWL_DSI_BLLP_MODE, 0x1);
   311		nwl_dsi_write(dsi, NWL_DSI_USE_NULL_PKT_BLLP, 0x0);
   312		nwl_dsi_write(dsi, NWL_DSI_VC, 0x0);
   313	
   314		nwl_dsi_write(dsi, NWL_DSI_PIXEL_PAYLOAD_SIZE, dsi->mode.hdisplay);
   315		nwl_dsi_write(dsi, NWL_DSI_VACTIVE, dsi->mode.vdisplay - 1);
   316		nwl_dsi_write(dsi, NWL_DSI_VBP, vback_porch);
   317		nwl_dsi_write(dsi, NWL_DSI_VFP, vfront_porch);
   318	
   319		return 0;
   320	}
   321	

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