Re: [RFC/PATCH 08/10] [ARM] tegra: Add framebuffer driver

[Jaya Kumar <jayakumar.lkml@gmail.com>]

Hi Colin, Erik,

Interesting work.

I'd recommend CCing linux-fbdev as well in future so that fbdev folks
can also get a chance to review your new fbdev driver.

On Tue, Mar 16, 2010 at 2:41 PM,  <konkers@google.com> wrote:
> From: Colin Cross <ccross@android.com>
>
> Signed-off-by: Colin Cross <ccross@android.com>
> Signed-off-by: Erik Gilling <konkers@android.com>
> ---
>  arch/arm/mach-tegra/include/mach/tegra_fb.h |   24 +
>  drivers/video/Kconfig                       |   11 +
>  drivers/video/Makefile                      |    1 +
>  drivers/video/tegrafb.c                     |  620 +++++++++++++++++++++++++++
>  4 files changed, 656 insertions(+), 0 deletions(-)
>  create mode 100644 arch/arm/mach-tegra/include/mach/tegra_fb.h
>  create mode 100644 drivers/video/tegrafb.c
>
> diff --git a/arch/arm/mach-tegra/include/mach/tegra_fb.h b/arch/arm/mach-tegra/include/mach/tegra_fb.h
> new file mode 100644
> index 0000000..f173544
> --- /dev/null
> +++ b/arch/arm/mach-tegra/include/mach/tegra_fb.h
> @@ -0,0 +1,24 @@
> +/*
> + * arch/arm/mach-tegra/include/mach/tegra_fb.h
> + *
> + * Copyright (C) 2010 Google, Inc.
> + * Author: Colin Cross <ccross@android.com>
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +struct tegra_fb_lcd_data {
> +       int     fb_xres;
> +       int     fb_yres;
> +       int     lcd_xres;
> +       int     lcd_yres;
> +       int     bits_per_pixel;
> +};

I'm trying to understand what's the difference between fb and lcd *res.

> diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
> index 5a5c303..b2e68e2 100644
> --- a/drivers/video/Kconfig
> +++ b/drivers/video/Kconfig
> @@ -1074,6 +1074,17 @@ config FB_RIVA_BACKLIGHT
>        help
>          Say Y here if you want to control the backlight of your display.
>
> +config FB_TEGRA
> +       tristate "NVIDIA Tegra SoC display support"
> +       depends on ARCH_TEGRA && FB = y
> +       select FB_CFB_FILLRECT
> +       select FB_CFB_COPYAREA
> +       select FB_CFB_IMAGEBLIT
> +       default FB
> +       help
> +         This driver supports the NVIDIA Tegra systems-on-a-chip.  This
> +         driver can not be compiled as a module.

Out of curiosity, why not?

> +
>  config FB_I810
>        tristate "Intel 810/815 support (EXPERIMENTAL)"
>        depends on EXPERIMENTAL && FB && PCI && X86_32 && AGP_INTEL
> diff --git a/drivers/video/Makefile b/drivers/video/Makefile
> index 4ecb30c..d4a14f2 100644
> --- a/drivers/video/Makefile
> +++ b/drivers/video/Makefile
> @@ -129,6 +129,7 @@ obj-$(CONFIG_XEN_FBDEV_FRONTEND)  += xen-fbfront.o
>  obj-$(CONFIG_FB_CARMINE)          += carminefb.o
>  obj-$(CONFIG_FB_MB862XX)         += mb862xx/
>  obj-$(CONFIG_FB_MSM)              += msm/
> +obj-$(CONFIG_FB_TEGRA)            += tegrafb.o
>
>  # Platform or fallback drivers go here
>  obj-$(CONFIG_FB_UVESA)            += uvesafb.o
> diff --git a/drivers/video/tegrafb.c b/drivers/video/tegrafb.c
> new file mode 100644
> index 0000000..634022b
> --- /dev/null
> +++ b/drivers/video/tegrafb.c
> @@ -0,0 +1,620 @@
> +/*
> + * drivers/video/tegrafb.c
> + *
> + * Copyright (C) 2010 Google, Inc.
> + * Author: Colin Cross <ccross@android.com>
> + *         Travis Geiselbrecht <travis@palm.com>
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/fb.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/string.h>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/delay.h>
> +#include <linux/platform_device.h>
> +#include <linux/interrupt.h>
> +#include <linux/clk.h>
> +#include <linux/wait.h>
> +#include <asm/cacheflush.h>
> +#include <mach/tegra_fb.h>
> +
> +#define DEBUG 1

You want to enable Debug by default for everyone?

> +
> +struct tegra_fb_info {
> +       struct clk *clk;
> +       struct resource *reg_mem;
> +       struct resource *fb_mem;
> +       void __iomem *reg_base;
> +       wait_queue_head_t event_wq;
> +       unsigned int wait_condition;
> +       int lcd_xres;
> +       int lcd_yres;
> +       int irq;
> +};

I think a comment about lcd_.res would help us understand what its
used for and how it differs from fb_.res. How come it is being
duplicated in multiple structures?

> +static int tegra_fb_cursor(struct fb_info *info, struct fb_cursor *cursor)
> +{
> +       return 0;
> +}
> +
> +static int tegra_fb_sync(struct fb_info *info)
> +{
> +       return 0;
> +}

Out of curiosity, why populate these functions if they don't do anything?

> +
> +#ifdef DEBUG
> +#define DUMP_REG(a) pr_info("%-32s\t%03x\t%08x\n", #a, a, tegra_fb_readl(tegra_fb, a));

Could pr_debug be useful above?

> +static struct fb_ops tegra_fb_ops = {
> +       .fb_cursor = tegra_fb_cursor,
> +       .fb_sync = tegra_fb_sync,

These 2 were the empty functions from above. I'm guessing this isn't needed.

> +
> +static int tegra_plat_remove(struct platform_device *pdev)
> +{
> +       struct fb_info *fb = platform_get_drvdata(pdev);
> +       struct tegra_fb_info *tegra_fb = fb->par;
> +       clk_disable(tegra_fb->clk);
> +       iounmap(fb->screen_base);
> +       release_resource(tegra_fb->fb_mem);
> +       iounmap(tegra_fb->reg_base);
> +       release_resource(tegra_fb->reg_mem);
> +       framebuffer_release(fb);
> +       return 0;
> +}
> +

I didn't read through carefully but shouldn't there be an
unregister_framebuffer in above? Wouldn't the above cause a free while
the structures could still in use by fb*?

Thanks,
jaya