[Intel-gfx] [PATCH] drm/i915/fbdev: Stop repeating tile configuration on stagnation

[Chris Wilson]

On Mon, Feb 20, 2017 at 04:37:47PM +0100, Tomasz Lis wrote:
> I tested this variant (reverted the change to "pass" variable before
> testing), and it fixes the issue with count=0 as well as possible
> infinite loop issue.
> 
> But something needs to be done with the "pass" var, one way or the
> other - commented below.
> 
> 
> W dniu 2017-02-18 o 16:37, Chris Wilson pisze:
> >If we cease making progress in finding matching outputs for a tiled
> >configuration, stop looping over the remaining unconfigured outputs.
> >
> >Fixes: b0ee9e7fa5b4 ("drm/fb: add support for tiled monitor configurations. (v2)")
> >Cc: Tomasz Lis <tomasz.lis at intel.com>
> >Cc: Dave Airlie <airlied at redhat.com>
> >Cc: Daniel Vetter <daniel.vetter at intel.com>
> >Cc: Jani Nikula <jani.nikula at linux.intel.com>
> >Cc: Sean Paul <seanpaul at chromium.org>
> >Cc: <stable at vger.kernel.org> # v3.19+
> >---
> >  drivers/gpu/drm/i915/intel_fbdev.c | 7 +++----
> >  1 file changed, 3 insertions(+), 4 deletions(-)
> >
> >diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
> >index 041322fef607..32d0af6b07a7 100644
> >--- a/drivers/gpu/drm/i915/intel_fbdev.c
> >+++ b/drivers/gpu/drm/i915/intel_fbdev.c
> >@@ -348,7 +348,7 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
> >  				    bool *enabled, int width, int height)
> >  {
> >  	struct drm_i915_private *dev_priv = to_i915(fb_helper->dev);
> >-	unsigned long conn_configured, mask;
> >+	unsigned long conn_configured, conn_seq, mask;
> >  	unsigned int count = min(fb_helper->connector_count, BITS_PER_LONG);
> >  	int i, j;
> >  	bool *save_enabled;
> >@@ -365,6 +365,7 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
> >  	mask = GENMASK(count - 1, 0);
> >  	conn_configured = 0;
> >  retry:
> >+	conn_seq = conn_configured;
> >  	for (i = 0; i < count; i++) {
> >  		struct drm_fb_helper_connector *fb_conn;
> >  		struct drm_connector *connector;
> >@@ -489,10 +490,8 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
> >  		conn_configured |= BIT(i);
> >  	}
> >-	if ((conn_configured & mask) != mask) {
> >-		pass++;
> This doesn't seem right; increasing the amount of passes should
> stay, or the use of "pass" variable should be completely replaced by
> conn_seq.

Good catch.

diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
index 32d0af6b07a7..f7e9a4e69595 100644
--- a/drivers/gpu/drm/i915/intel_fbdev.c
+++ b/drivers/gpu/drm/i915/intel_fbdev.c
@@ -355,7 +355,6 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
        bool fallback = true;
        int num_connectors_enabled = 0;
        int num_connectors_detected = 0;
-       int pass = 0;
 
        save_enabled = kcalloc(count, sizeof(bool), GFP_KERNEL);
        if (!save_enabled)
@@ -379,7 +378,7 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
                if (conn_configured & BIT(i))
                        continue;
 
-               if (pass == 0 && !connector->has_tile)
+               if (conn_seq == 0 && !connector->has_tile)
                        continue;
 
                if (connector->status == connector_status_connected)

Suggestions for a better name than conn_seq much appreciated.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre