Re: [PATCH v2] OMAPDSS: DISPC: Improve DIGIT channel sync signal selection

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On Mon, 2012-07-30 at 19:11 -0500, Ricardo Neri wrote:
> DSS code wrongly assumes that VENC is always available as source for the external
> sync signal for the display controller DIGIT channel. One cannot blindly
> rely only on the value of DSS_CONTROL[15] as on certain processors (e.g., OMAP5)
> reading/writing on that bit may not be valid. If the the sync source is not read
> correctly, the callers of dss_get_hdmi_venc_clk_source might make wrong assumptions
> about, for instance, video timings.
> 
> This patch adds logic to correctly get the sync signal based on the
> available displays in the DIGIT channel. A kernel BUG is thrown if an
> invalid source is selected.
> 
> Signed-off-by: Ricardo Neri <ricardo.neri@ti.com>
> ---
> v2: use BUG_ON() to simplify handling of invalid cases.
>  drivers/video/omap2/dss/dss.c |   13 +++++++++++--
>  1 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/omap2/dss/dss.c b/drivers/video/omap2/dss/dss.c
> index 04b4586..2f8e4b6 100644
> --- a/drivers/video/omap2/dss/dss.c
> +++ b/drivers/video/omap2/dss/dss.c
> @@ -648,9 +648,15 @@ void dss_set_dac_pwrdn_bgz(bool enable)
>  	REG_FLD_MOD(DSS_CONTROL, enable, 5, 5);	/* DAC Power-Down Control */
>  }
>  
> -void dss_select_hdmi_venc_clk_source(enum dss_hdmi_venc_clk_source_select hdmi)
> +void dss_select_hdmi_venc_clk_source(enum dss_hdmi_venc_clk_source_select src)
>  {
> -	REG_FLD_MOD(DSS_CONTROL, hdmi, 15, 15);	/* VENC_HDMI_SWITCH */
> +	enum omap_display_type dp;
> +	dp = dss_feat_get_supported_displays(OMAP_DSS_CHANNEL_DIGIT);
> +
> +	BUG_ON((src == DSS_VENC_TV_CLK) && !(dp & OMAP_DISPLAY_TYPE_VENC));
> +	BUG_ON((src == DSS_HDMI_M_PCLK) && !(dp & OMAP_DISPLAY_TYPE_HDMI));
> +
> +	REG_FLD_MOD(DSS_CONTROL, src, 15, 15);	/* VENC_HDMI_SWITCH */
>  }

This one will still write to the reserved bit 15 on OMAP5.

Perhaps we could check if both VENC and HDMI are supported, and if not,
return.

 Tomi


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