[Acked] [Quantal][PATCH] drm/i915: Make data/link N value power of two

[Andy Whitcroft]

On Mon, Sep 23, 2013 at 06:42:58PM +0800, Adam Lee wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1212376
> 
> The BIOS uses power of two values for the data/link N value.
> 
> Follow suit to make the Zotac DP to dual-HDMI dongle work.
> 
> v2: Clean up the magic numbers and defines
>     Change the N clamping to be a bit easier on the eye
>     Rename intel_reduce_ratio to intel_reduce_m_n_ratio
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=49402
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=59810
> Tested-by:  Jesse Barnes <jbarnes at virtuousgeek.org>
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> [Haitao Zhang: backport to 3.8 from commit a65851af59387146a28a928c3e7bb17dabc5db72 upstream]
> Signed-off-by: Haitao Zhang <haitao.zhang at canonical.com>
> Signed-off-by: Kamal Mostafa <kamal at canonical.com>
> Signed-off-by: Brad Figg <brad.figg at canonical.com>
> (cherry picked from commit b92ae13bf2b9610bef48c1b64c0b4dcdf47a4053 ubuntu-raring)
> Cc: Timo Aaltonen <timo.aaltonen at canonical.com>
> Signed-off-by: Adam Lee <adam.lee at canonical.com>
> ---
>  ubuntu/i915/i915_reg.h      | 12 ++++--------
>  ubuntu/i915/intel_display.c | 23 +++++++++++++++--------
>  2 files changed, 19 insertions(+), 16 deletions(-)
> 
> diff --git a/ubuntu/i915/i915_reg.h b/ubuntu/i915/i915_reg.h
> index ce70f0a..da24f9c 100644
> --- a/ubuntu/i915/i915_reg.h
> +++ b/ubuntu/i915/i915_reg.h
> @@ -2603,14 +2603,14 @@
>  #define _PIPEB_GMCH_DATA_M			0x71050
>  
>  /* Transfer unit size for display port - 1, default is 0x3f (for TU size 64) */
> -#define   PIPE_GMCH_DATA_M_TU_SIZE_MASK		(0x3f << 25)
> -#define   PIPE_GMCH_DATA_M_TU_SIZE_SHIFT	25
> +#define  TU_SIZE(x)             (((x)-1) << 25) /* default size 64 */
> +#define  TU_SIZE_MASK           (0x3f << 25)
>  
> -#define   PIPE_GMCH_DATA_M_MASK			(0xffffff)
> +#define  DATA_LINK_M_N_MASK	(0xffffff)
> +#define  DATA_LINK_N_MAX	(0x800000)
>  
>  #define _PIPEA_GMCH_DATA_N			0x70054
>  #define _PIPEB_GMCH_DATA_N			0x71054
> -#define   PIPE_GMCH_DATA_N_MASK			(0xffffff)
>  
>  /*
>   * Computing Link M and N values for the Display Port link
> @@ -2625,11 +2625,9 @@
>  
>  #define _PIPEA_DP_LINK_M				0x70060
>  #define _PIPEB_DP_LINK_M				0x71060
> -#define   PIPEA_DP_LINK_M_MASK			(0xffffff)
>  
>  #define _PIPEA_DP_LINK_N				0x70064
>  #define _PIPEB_DP_LINK_N				0x71064
> -#define   PIPEA_DP_LINK_N_MASK			(0xffffff)
>  
>  #define PIPE_GMCH_DATA_M(pipe) _PIPE(pipe, _PIPEA_GMCH_DATA_M, _PIPEB_GMCH_DATA_M)
>  #define PIPE_GMCH_DATA_N(pipe) _PIPE(pipe, _PIPEA_GMCH_DATA_N, _PIPEB_GMCH_DATA_N)
> @@ -3295,8 +3293,6 @@
>  
>  
>  #define _PIPEA_DATA_M1           0x60030
> -#define  TU_SIZE(x)             (((x)-1) << 25) /* default size 64 */
> -#define  TU_SIZE_MASK           0x7e000000
>  #define  PIPE_DATA_M1_OFFSET    0
>  #define _PIPEA_DATA_N1           0x60034
>  #define  PIPE_DATA_N1_OFFSET    0
> diff --git a/ubuntu/i915/intel_display.c b/ubuntu/i915/intel_display.c
> index 31dcfa4..52d639d 100644
> --- a/ubuntu/i915/intel_display.c
> +++ b/ubuntu/i915/intel_display.c
> @@ -4042,26 +4042,33 @@ struct fdi_m_n {
>  static void
>  fdi_reduce_ratio(u32 *num, u32 *den)
>  {
> -	while (*num > 0xffffff || *den > 0xffffff) {
> +	while (*num > DATA_LINK_M_N_MASK ||
> +	       *den > DATA_LINK_M_N_MASK) {
>  		*num >>= 1;
>  		*den >>= 1;
>  	}
>  }
>  
> +static void compute_m_n(unsigned int m, unsigned int n,
> +			uint32_t *ret_m, uint32_t *ret_n)
> +{
> +	*ret_n = min_t(unsigned int, roundup_pow_of_two(n), DATA_LINK_N_MAX);
> +	*ret_m = div_u64((uint64_t) m * *ret_n, n);
> +	fdi_reduce_ratio(ret_m, ret_n);
> +}
> +
>  static void
>  ironlake_compute_m_n(int bits_per_pixel, int nlanes, int pixel_clock,
>  		     int link_clock, struct fdi_m_n *m_n)
>  {
>  	m_n->tu = 64; /* default size */
>  
> -	/* BUG_ON(pixel_clock > INT_MAX / 36); */
> -	m_n->gmch_m = bits_per_pixel * pixel_clock;
> -	m_n->gmch_n = link_clock * nlanes * 8;
> -	fdi_reduce_ratio(&m_n->gmch_m, &m_n->gmch_n);
> +	compute_m_n(bits_per_pixel * pixel_clock,
> +		    link_clock * nlanes * 8,
> +		    &m_n->gmch_m, &m_n->gmch_n);
>  
> -	m_n->link_m = pixel_clock;
> -	m_n->link_n = link_clock;
> -	fdi_reduce_ratio(&m_n->link_m, &m_n->link_n);
> +	compute_m_n(pixel_clock, link_clock,
> +		    &m_n->link_m, &m_n->link_n);
>  }
>  
>  static inline bool intel_panel_use_ssc(struct drm_i915_private *dev_priv)

Seems to do what is claimed (as much as just reading code can prove) and
looks to match what is applied to R.

Acked-by: Andy Whitcroft <apw at canonical.com>

-apw