linux-kernel - Re: [PATCH] drm/pl111: Add a debugfs node to dump our registers.

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Message-ID: <20170518100804.vnqomuzeligkltby@imgtec.com>
Date:   Thu, 18 May 2017 11:08:04 +0100
From:   Eric Engestrom <eric.engestrom@...tec.com>
To:     Eric Anholt <eric@...olt.net>
CC:     <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/pl111: Add a debugfs node to dump our registers.

On Wednesday, 2017-05-17 17:56:40 -0700, Eric Anholt wrote:
> While debugging an X11 display failure, I wanted to see where we were
> actually scanning out from.  This is probably generally useful to
> others that might be working on this device.
> 
> Signed-off-by: Eric Anholt <eric@...olt.net>
> ---
>  drivers/gpu/drm/pl111/Makefile        |  2 ++
>  drivers/gpu/drm/pl111/pl111_debugfs.c | 55 +++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/pl111/pl111_drm.h     |  3 ++
>  drivers/gpu/drm/pl111/pl111_drv.c     |  4 +++
>  4 files changed, 64 insertions(+)
>  create mode 100644 drivers/gpu/drm/pl111/pl111_debugfs.c
> 
> diff --git a/drivers/gpu/drm/pl111/Makefile b/drivers/gpu/drm/pl111/Makefile
> index 01caee727c13..59483d610ef5 100644
> --- a/drivers/gpu/drm/pl111/Makefile
> +++ b/drivers/gpu/drm/pl111/Makefile
> @@ -2,4 +2,6 @@ pl111_drm-y +=	pl111_connector.o \
>  		pl111_display.o \
>  		pl111_drv.o
>  
> +pl111_drm-$(CONFIG_DEBUG_FS) += pl111_debugfs.o
> +
>  obj-$(CONFIG_DRM_PL111) += pl111_drm.o
> diff --git a/drivers/gpu/drm/pl111/pl111_debugfs.c b/drivers/gpu/drm/pl111/pl111_debugfs.c
> new file mode 100644
> index 000000000000..ee13a060cddf
> --- /dev/null
> +++ b/drivers/gpu/drm/pl111/pl111_debugfs.c
> @@ -0,0 +1,55 @@
> +/*
> + *  Copyright © 2017 Broadcom
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/amba/clcd-regs.h>
> +#include <linux/seq_file.h>
> +#include <drm/drm_debugfs.h>
> +#include <drm/drmP.h>
> +#include "pl111_drm.h"
> +
> +#define REGDEF(reg) { reg, #reg }
> +static const struct {
> +	uint32_t reg;
> +	const char *name;
> +} pl111_reg_defs[] = {
> +	REGDEF(CLCD_TIM0),
> +	REGDEF(CLCD_TIM1),
> +	REGDEF(CLCD_TIM2),
> +	REGDEF(CLCD_TIM3),
> +	REGDEF(CLCD_UBAS),
> +	REGDEF(CLCD_PL111_CNTL),
> +	REGDEF(CLCD_PL111_IENB),
> +};
> +
> +int pl111_debugfs_regs(struct seq_file *m, void *unused)
> +{
> +	struct drm_info_node *node = (struct drm_info_node *)m->private;
> +	struct drm_device *dev = node->minor->dev;
> +	struct pl111_drm_dev_private *priv = dev->dev_private;
> +	int i;

nit: this will print a warning; s/int/unsigned/ ?

PS: I love how little code everything in this driver takes :]

> +
> +	for (i = 0; i < ARRAY_SIZE(pl111_reg_defs); i++) {
> +		seq_printf(m, "%s (0x%04x): 0x%08x\n",
> +			   pl111_reg_defs[i].name, pl111_reg_defs[i].reg,
> +			   readl(priv->regs + pl111_reg_defs[i].reg));
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct drm_info_list pl111_debugfs_list[] = {
> +	{"regs", pl111_debugfs_regs, 0},
> +};
> +
> +int
> +pl111_debugfs_init(struct drm_minor *minor)
> +{
> +	return drm_debugfs_create_files(pl111_debugfs_list,
> +					ARRAY_SIZE(pl111_debugfs_list),
> +					minor->debugfs_root, minor);
> +}
> diff --git a/drivers/gpu/drm/pl111/pl111_drm.h b/drivers/gpu/drm/pl111/pl111_drm.h
> index 4162c6aa5dbb..5c685bfc8fdc 100644
> --- a/drivers/gpu/drm/pl111/pl111_drm.h
> +++ b/drivers/gpu/drm/pl111/pl111_drm.h
> @@ -25,6 +25,8 @@
>  
>  #define CLCD_IRQ_NEXTBASE_UPDATE BIT(2)
>  
> +struct drm_minor;
> +
>  struct pl111_drm_connector {
>  	struct drm_connector connector;
>  	struct drm_panel *panel;
> @@ -60,5 +62,6 @@ int pl111_encoder_init(struct drm_device *dev);
>  int pl111_dumb_create(struct drm_file *file_priv,
>  		      struct drm_device *dev,
>  		      struct drm_mode_create_dumb *args);
> +int pl111_debugfs_init(struct drm_minor *minor);
>  
>  #endif /* _PL111_DRM_H_ */
> diff --git a/drivers/gpu/drm/pl111/pl111_drv.c b/drivers/gpu/drm/pl111/pl111_drv.c
> index 9d1467492cb9..f79c24859a30 100644
> --- a/drivers/gpu/drm/pl111/pl111_drv.c
> +++ b/drivers/gpu/drm/pl111/pl111_drv.c
> @@ -173,6 +173,10 @@ static struct drm_driver pl111_drm_driver = {
>  	.gem_prime_import_sg_table = drm_gem_cma_prime_import_sg_table,
>  	.gem_prime_export = drm_gem_prime_export,
>  	.gem_prime_get_sg_table	= drm_gem_cma_prime_get_sg_table,
> +
> +#if defined(CONFIG_DEBUG_FS)
> +	.debugfs_init = pl111_debugfs_init,
> +#endif
>  };
>  
>  #ifdef CONFIG_ARM_AMBA
> -- 
> 2.11.0
>