[Intel-gfx] [PATCH 4/5] drm/i915: fix VLV limits and m/n/p calculations v2

[Daniel Vetter]

On Wed, Apr 17, 2013 at 03:55:00PM -0700, Jesse Barnes wrote:
> From: Pallavi G <pallavi.g at intel.com>
> 
> For high res modes m n p calculation is fixed for VLV platform.
> 
> v2: use 64 bit types and math (Ville)
> 
> Signed-off-by: Pallavi G <pallavi.g at intel.com>
> Signed-off-by: Vijay Purushothaman <vijay.a.purushothaman at intel.com>
> Signed-off-by: Yogesh M <yogesh.mohan.marimuthu at intel.com>
> Signed-off-by: Gajanan Bhat <gajanan.bhat at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c |   25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 28b8fac..f3aa24f4 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -31,6 +31,7 @@
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
>  #include <linux/vgaarb.h>
> +#include <linux/math64.h>
>  #include <drm/drm_edid.h>
>  #include <drm/drmP.h>
>  #include "intel_drv.h"
> @@ -396,21 +397,21 @@ static const intel_limit_t intel_limits_vlv_dac = {
>  	.m1 = { .min = 2, .max = 3 },
>  	.m2 = { .min = 11, .max = 156 },
>  	.p = { .min = 10, .max = 30 },
> -	.p1 = { .min = 2, .max = 3 },
> +	.p1 = { .min = 1, .max = 3 },
>  	.p2 = { .dot_limit = 270000,
>  		.p2_slow = 2, .p2_fast = 20 },
>  	.find_pll = intel_vlv_find_best_pll,
>  };
>  
>  static const intel_limit_t intel_limits_vlv_hdmi = {
> -	.dot = { .min = 20000, .max = 165000 },
> -	.vco = { .min = 4000000, .max = 5994000},
> -	.n = { .min = 1, .max = 7 },
> +	.dot = { .min = 25000, .max = 180000 },
> +	.vco = { .min = 4040000, .max = 5960000 },
> +	.n = { .min = 1, .max = 5 },
>  	.m = { .min = 60, .max = 300 }, /* guess */
>  	.m1 = { .min = 2, .max = 3 },
> -	.m2 = { .min = 11, .max = 156 },
> +	.m2 = { .min = 15, .max = 149 },
>  	.p = { .min = 10, .max = 30 },
> -	.p1 = { .min = 2, .max = 3 },
> +	.p1 = { .min = 1, .max = 3 },
>  	.p2 = { .dot_limit = 270000,
>  		.p2_slow = 2, .p2_fast = 20 },
>  	.find_pll = intel_vlv_find_best_pll,
> @@ -424,7 +425,7 @@ static const intel_limit_t intel_limits_vlv_dp = {
>  	.m1 = { .min = 2, .max = 3 },
>  	.m2 = { .min = 11, .max = 156 },
>  	.p = { .min = 10, .max = 30 },
> -	.p1 = { .min = 2, .max = 3 },
> +	.p1 = { .min = 1, .max = 3 },
>  	.p2 = { .dot_limit = 270000,
>  		.p2_slow = 2, .p2_fast = 20 },
>  	.find_pll = intel_vlv_find_best_pll,
> @@ -821,10 +822,13 @@ intel_vlv_find_best_pll(const intel_limit_t *limit, struct drm_crtc *crtc,
>  			int target, int refclk, intel_clock_t *match_clock,
>  			intel_clock_t *best_clock)
>  {
> +#define LONG_OVERFLOW 0x7FFFFFFF
> +#define DIFF_OVERFLOW (LONG_OVERFLOW/10000)

Unused?

> +
>  	u32 p1, p2, m1, m2, vco, bestn, bestm1, bestm2, bestp1, bestp2;
>  	u32 m, n, fastclk;
>  	u32 updrate, minupdate, fracbits, p;
> -	unsigned long bestppm, ppm, absppm;
> +	s64 bestppm, ppm, absppm, ppmdiff;
>  	int dotclk, flag;
>  
>  	flag = 0;
> @@ -853,8 +857,9 @@ intel_vlv_find_best_pll(const intel_limit_t *limit, struct drm_crtc *crtc,
>  					m = m1 * m2;
>  					vco = updrate * m;
>  					if (vco >= limit->vco.min && vco < limit->vco.max) {
> -						ppm = 1000000 * ((vco / p) - fastclk) / fastclk;
> -						absppm = (ppm > 0) ? ppm : (-ppm);
> +						ppmdiff = div_s64((100*vco), p) - (100*fastclk);

I'm probably a bit dense, but I think C integer conversion rules say
(100*vco) is still only a u32. So I think that div_s64 doesn't help a lot
since the upcast to u64 will happen after the mutliplication.  Also,
ppmdiff should be called pphundred_diff if you want to stick to this
formula.
-Daniel

> +						absppm = div_s64((abs64(ppmdiff)*10000), fastclk);
> +
>  						if (absppm < 100 && ((p1 * p2) > (bestp1 * bestp2))) {
>  							bestppm = 0;
>  							flag = 1;
> -- 
> 1.7.10.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch