linux-kernel - Re: [RFC PATCH v3 1/4] drm: Introduce generic probe function for component based masters.

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Message-ID: <20151109105316.GD963@e106497-lin.cambridge.arm.com>
Date:	Mon, 9 Nov 2015 10:53:16 +0000
From:	Liviu Dudau <Liviu.Dudau@....com>
To:	Mark yao <mark.yao@...k-chips.com>
Cc:	David Airlie <airlied@...ux.ie>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Heiko Stuebner <heiko@...ech.de>,
	Russell King <rmk+kernel@....linux.org.uk>,
	linux-rockchip <linux-rockchip@...ts.infradead.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v3 1/4] drm: Introduce generic probe function for
 component based masters.

On Mon, Nov 09, 2015 at 05:39:25PM +0800, Mark yao wrote:
> On 2015年10月19日 23:07, Liviu Dudau wrote:
> >A lot of component based DRM drivers use a variant of the same code
> >as the probe function. They bind the crtc ports in the first iteration
> >and then scan through the child nodes and bind the encoders attached
> >to the remote endpoints. Factor the common code into a separate
> >function called drm_of_component_probe() in order to increase code
> >reuse.
> >
> >Cc: David Airlie <airlied@...ux.ie>
> >Signed-off-by: Liviu Dudau <Liviu.Dudau@....com>
> >---
> >  drivers/gpu/drm/drm_of.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  include/drm/drm_of.h     | 13 +++++++
> >  2 files changed, 101 insertions(+)
> >
> >diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >index be38840..493c05c 100644
> >--- a/drivers/gpu/drm/drm_of.c
> >+++ b/drivers/gpu/drm/drm_of.c
> >@@ -1,3 +1,4 @@
> >+#include <linux/component.h>
> >  #include <linux/export.h>
> >  #include <linux/list.h>
> >  #include <linux/of_graph.h>
> >@@ -61,3 +62,90 @@ uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >  	return possible_crtcs;
> >  }
> >  EXPORT_SYMBOL(drm_of_find_possible_crtcs);
> >+
> >+/**
> >+ * drm_of_component_probe - Generic probe function for a component based master
> >+ * @dev: master device containing the OF node
> >+ * @compare_of: compare function used for matching components
> >+ * @master_ops: component master ops to be used
> >+ *
> >+ * Parse the platform device OF node and bind all the components associated
> >+ * with the master. Interface ports are added before the encoders in order to
> >+ * satisfy their .bind requirements
> >+ * See Documentation/devicetree/bindings/graph.txt for the bindings.
> >+ *
> >+ * Returns zero if successful, or one of the standard error codes if it fails.
> >+ */
> >+int drm_of_component_probe(struct device *dev,
> >+			   int (*compare_of)(struct device *, void *),
> >+			   const struct component_master_ops *m_ops)
> >+{
> >+	struct device_node *ep, *port, *remote;
> >+	struct component_match *match = NULL;
> >+	int i;
> >+
> >+	if (!dev->of_node)
> >+		return -EINVAL;
> >+
> >+	/*
> >+	 * Bind the crtc's ports first, so that drm_of_find_possible_crtcs()
> >+	 * called from encoder's .bind callbacks works as expected
> >+	 */
> >+	for (i = 0; ; i++) {
> >+		port = of_parse_phandle(dev->of_node, "ports", i);
> >+		if (!port)
> >+			break;
> >+
> >+		if (!of_device_is_available(port->parent)) {
> >+			of_node_put(port);
> >+			continue;
> >+		}
> >+
> >+		component_match_add(dev, &match, compare_of, port);
> Hi Liviu
>       Rockchip drm can't work with drm_of_component_probe function now,
> 
>       At drm_of_component_probe:
>             component_match_add(dev, &match, compare_of, port);
>       And original rockchip drm use:
>             component_match_add(dev, &match, compare_of, port->parent);
> 
>      That different "port" and "port->parent" cause crtc device node always
> mis-match.
> 
>      I'm confused that rockchip use same dts node map as imx drm driver, but
> it works
> for imx drm, not work on rockchip drm.

Hi Mark,

I'm (slightly) confused as well. The drivers are different so there must be a reason
to account for the different behaviour. Unfortunately I don't have a Rockchip based
platform ready for testing, so I would appreciate if you could add some debugging
messages to drm_of_component_probe() when component_match_add is being called and
compare that with the version before my patch.

Best regards,
Liviu

> 
> >+		of_node_put(port);
> >+	}
> >
> -- Ｍark Yao
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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