On Wed, Mar 10, 2010 at 10:58 AM, <Tomi.Valkeinen@xxxxxxxxx> wrote:
> I haven't had time to look at this, but I don't think your analysis is correct.
You are correct of course. My sleepy eyes neglected to notice that
double = and that makes a big difference :-)
> What first comes to my mind is that dss.dispc_clk_source is, for some reason, uninitialized. Could you put prints to dss_select_dispc_clk_source to see if it's called, and if so, what is assigned to dss.dispc_clk_source?
I did a build with that change and it does seem that
dss_select_dispc_clk_source is never called.
Steve
> Tomi
>
> ________________________________________
> From: ext Steve Sakoman [sakoman@xxxxxxxxx]
> Sent: Wednesday, March 10, 2010 20:42
> To: linux-omap@xxxxxxxxxxxxxxx; Valkeinen Tomi (Nokia-D/Helsinki)
> Subject: Re: kernel panic with latest DSS
>
> On Wed, Mar 10, 2010 at 10:16 AM, Steve Sakoman <sakoman@xxxxxxxxx> wrote:
>
>> The issue occurs in the following section of code in
>> drivers/video/omap2/dss/dispc.c:
>>
>> unsigned long dispc_fclk_rate(void)
>> {
>> unsigned long r = 0;
>>
>> if (dss_get_dispc_clk_source() == DSS_SRC_DSS1_ALWON_FCLK)
>> r = dss_clk_get_rate(DSS_CLK_FCK1);
>> else
>> #ifdef CONFIG_OMAP2_DSS_DSI
>> r = dsi_get_dsi1_pll_rate();
>> #else
>> BUG();
>> #endif
>> return r;
>> }
>>
>> Since my machines don't have DSI displays CONFIG_OMAP2_DSS_DSI is not
>> defined and the BUG() call is triggered.
>
> The issue seems to be the test for DSS_SRC_DSS1_ALWON_FCLK.
>
> Looking at drivers/video/omap2/dss/dispc.c I see that
> DSS_SRC_DSS1_ALWON_FCLK will never be returned since clk_src is always
> set to 0 or 1 based on a test of DSS_SRC_DSS1_ALWON_FCLK :
>
> void dss_select_dispc_clk_source(enum dss_clk_source clk_src)
> {
> int b;
>
> BUG_ON(clk_src != DSS_SRC_DSI1_PLL_FCLK &&
> clk_src != DSS_SRC_DSS1_ALWON_FCLK);
>
> b = clk_src == DSS_SRC_DSS1_ALWON_FCLK ? 0 : 1;
>
> REG_FLD_MOD(DSS_CONTROL, b, 0, 0); /* DISPC_CLK_SWITCH */
>
> dss.dispc_clk_source = clk_src;
> }
>
> It seems to me that the test should return to the way it was in the
> previous DSS version, i.e. a test for 0:
>
> diff --git a/drivers/video/omap2/dss/dispc.c b/drivers/video/omap2/dss/dispc.c
> index e777e35..be9b3de 100644
> --- a/drivers/video/omap2/dss/dispc.c
> +++ b/drivers/video/omap2/dss/dispc.c
> @@ -2218,7 +2218,7 @@ unsigned long dispc_fclk_rate(void)
> {
> unsigned long r = 0;
>
> - if (dss_get_dispc_clk_source() == DSS_SRC_DSS1_ALWON_FCLK)
> + if (dss_get_dispc_clk_source() == 0)
> r = dss_clk_get_rate(DSS_CLK_FCK1);
> else
> #ifdef CONFIG_OMAP2_DSS_DSI
>
> A test build confirms that this change restores my ability to play
> DVD's and display webcam streams. My understanding of this code is
> superficial, so hopefully Tomi can comment on whether this is a good
> fix or not.
>
> Steve
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