Messages in this thread | | | Date | Thu, 23 May 2013 15:00:39 +0200 | From | "" <> | Subject | Re: mxsfb: DATA_FORMAT_24_BIT flag outputs invalid colours |
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Hi Hector,
On Thu, May 23, 2013 at 01:55:28PM +0200, Hector Palacios wrote: > Hello, > > I'm using an i.MX28 based board with lcd connected with 18bits data bus. > My platform uses 32 bits per pixel: > > mxsfb_pdata.default_bpp = 32; > mxsfb_pdata.ld_intf_width = STMLCDIF_18BIT; > > With these settings the mxsfb.c driver sets flag DATA_FORMAT_24_BIT > at HW_LCDIF_CTRL register in function mxsfb_set_par(): > > case 32: > dev_dbg(&host->pdev->dev, "Setting up RGB888/666 mode\n"); > ctrl |= CTRL_SET_WORD_LENGTH(3); > switch (host->ld_intf_width) { > case STMLCDIF_8BIT: > dev_dbg(&host->pdev->dev, > "Unsupported LCD bus width mapping\n"); > return -EINVAL; > case STMLCDIF_16BIT: > case STMLCDIF_18BIT: > /* 24 bit to 18 bit mapping */ > ctrl |= CTRL_DF24; /* ignore the upper 2 bits in > * each colour component > */ > break; > case STMLCDIF_24BIT: > /* real 24 bit */ > break; > } > > According to the manual, this flag does: > 0x0: ALL_24_BITS_VALID: Data input to the block is in 24 bpp > format, such that all RGB 888 data is contained in 24 bits. > 0x1: DROP_UPPER_2_BITS_PER_BYTE — Data input to the block is > actually RGB 18 bpp, but there is 1 colour per byte, hence the upper > 2 bits in each byte do not contain any useful data, and should be > dropped. > > The setting of this flag is producing bad colours with true colour > images (i.e. the Linux penguin is displayed ok, but QT applications > or images displayed with fbv are not). > I believe the setting of this flag is not correct (after all, if my > bpp is 32, then all 24bit colours are useful and dropping the upper > 2 bits is a bad idea). > If I don't set it, then true colour images are displayed correctly. > The only problem is that the Linux penguin is displayed much darker > than usual (correct colours, but darker). Perhaps the 224 colour > format of this image justifies it? > > I noticed the cfa10049 platform also uses the same configuration (18 > bits data bus and 32bpp) and was wondering if true colour images are > correctly displayed in this platform with this flag set (for example > with fbv application [1]).
I had the exact same problem, and suggested the exact same solution a few weeks back.
https://patchwork.kernel.org/patch/2470441/
The conclusion of that discussion what that the userspace applications were not honouring the bitfield correctly set by the mxsfb driver, and as such, it was not a bug in the driver.
While this is correct, I wonder, now that since we had that same problem in a very short amount of time, if we couldn't set this behaviour dependant of some (dt? kernel argument?) property so that one could customise it anyway he want.
Maxime
-- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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