diff options
| author | Madhav Chauhan <madhav.chauhan@intel.com> | 2017-04-05 09:04:23 -0400 |
|---|---|---|
| committer | Jani Nikula <jani.nikula@intel.com> | 2017-04-06 14:45:26 +0300 |
| commit | 97f55ca5b6625bb4ddeca7b1272b53ca04ab3cf0 (patch) | |
| tree | bb5cdbc0cb9916c3e493c5bb9b837e446a4d7262 /drivers/gpu/drm/i915/intel_cdclk.c | |
| parent | 68f357cb734738d60a749abb6673e7b63ccf0221 (diff) | |
drm/i915/glk: limit pixel clock to 99% of cdclk workaround
As per BSPEC, valid cdclk values for glk are 79.2, 158.4, 316.8 Mhz.
Practically we can achive only 99% of these cdclk values (HW team
checking on this). So cdclk should be calculated for the given pixclk as
per that otherwise it may lead to screen corruption, explained below:
1. For DSI AUO panel(1920x1200 @60) required pixclk is 157100 KHZ
2. glk_calc_cdclk returns 79200 KHZ for this pixclk, For 2PPC it
will be 158400 KHZ
3. Practically 100% of the cdclk can’t be achieved, so 99% of 158400
KHZ = 156816 which is less than the desired pixlclk and causes
panel corruption.
v2: Rebased to new CDLCK code framework
v3: Addressed review comments from Ander/Jani
- Add comment in code about 99% usage of CDCLK
- Calculate max dot clock as well with 99% limit
v4 by Jani:
- drop superfluous whitespace change
- rewrite code comments to clarify
v5: Added details of non-working scenario in commit message
Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1491397463-13637-1-git-send-email-madhav.chauhan@intel.com
Diffstat (limited to 'drivers/gpu/drm/i915/intel_cdclk.c')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_cdclk.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/drivers/gpu/drm/i915/intel_cdclk.c b/drivers/gpu/drm/i915/intel_cdclk.c index dd3ad52b7dfe..763010f8ad89 100644 --- a/drivers/gpu/drm/i915/intel_cdclk.c +++ b/drivers/gpu/drm/i915/intel_cdclk.c @@ -1071,9 +1071,15 @@ static int bxt_calc_cdclk(int max_pixclk) static int glk_calc_cdclk(int max_pixclk) { - if (max_pixclk > 2 * 158400) + /* + * FIXME: Avoid using a pixel clock that is more than 99% of the cdclk + * as a temporary workaround. Use a higher cdclk instead. (Note that + * intel_compute_max_dotclk() limits the max pixel clock to 99% of max + * cdclk.) + */ + if (max_pixclk > DIV_ROUND_UP(2 * 158400 * 99, 100)) return 316800; - else if (max_pixclk > 2 * 79200) + else if (max_pixclk > DIV_ROUND_UP(2 * 79200 * 99, 100)) return 158400; else return 79200; @@ -1664,7 +1670,11 @@ static int intel_compute_max_dotclk(struct drm_i915_private *dev_priv) int max_cdclk_freq = dev_priv->max_cdclk_freq; if (IS_GEMINILAKE(dev_priv)) - return 2 * max_cdclk_freq; + /* + * FIXME: Limiting to 99% as a temporary workaround. See + * glk_calc_cdclk() for details. + */ + return 2 * max_cdclk_freq * 99 / 100; else if (INTEL_INFO(dev_priv)->gen >= 9 || IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) return max_cdclk_freq; |