linux-kernel - Re: [PATCH 6/8] omapfb: Condition mutex acquisition

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Message-ID: <6cb013310910031138k6086d1faje44d1582e5db9422@mail.gmail.com>
Date:	Sat, 3 Oct 2009 11:38:18 -0700
From:	Cory Maccarrone <darkstar6262@...il.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Imre Deak <imre.deak@...ia.com>,
	Sergio Aguirre <saaguirre@...com>, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Tomi Valkeinen <tomi.valkeinen@...ia.com>
Subject: Re: [PATCH 6/8] omapfb: Condition mutex acquisition

On Fri, Oct 2, 2009 at 3:44 PM, Tony Lindgren <tony@...mide.com> wrote:
>
> From: Sergio Aguirre <saaguirre@...com>
>
> This fixes a bug introduced by this commit ID:
>
>  commit 537a1bf059fa312355696fa6db80726e655e7f17
>  Author: Krzysztof Helt <krzysztof.h1@...pl>
>  Date:   Tue Jun 30 11:41:29 2009 -0700
>
>    fbdev: add mutex for fb_mmap locking
>
> In which a mutex was added when changing smem_start and smem_len fields,
> so the mutex inside the fb_mmap() call is actually used.
>
> The problem was that set_fb_fix, which modifies the above 2 fields,
> was called before and after registering the framebuffer,
> which when used before registration, lead to a failed attempt to
> use an uninitialized mutex.
>
> Solution: Don't use mutex before framebuffer registration.
>
> Signed-off-by: Sergio Aguirre <saaguirre@...com>
> Acked-by: Tomi Valkeinen <tomi.valkeinen@...ia.com>
> Acked-by: Imre Deak <imre.deak@...ia.com>
> Signed-off-by: Tony Lindgren <tony@...mide.com>
> ---
>  drivers/video/omap/omapfb_main.c |   22 ++++++++++++++--------
>  1 files changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/video/omap/omapfb_main.c b/drivers/video/omap/omapfb_main.c
> index 125e605..0d0c8c8 100644
> --- a/drivers/video/omap/omapfb_main.c
> +++ b/drivers/video/omap/omapfb_main.c
> @@ -393,7 +393,7 @@ static void omapfb_sync(struct fb_info *fbi)
>  * Set fb_info.fix fields and also updates fbdev.
>  * When calling this fb_info.var must be set up already.
>  */
> -static void set_fb_fix(struct fb_info *fbi)
> +static void set_fb_fix(struct fb_info *fbi, int from_init)
>  {
>        struct fb_fix_screeninfo *fix = &fbi->fix;
>        struct fb_var_screeninfo *var = &fbi->var;
> @@ -403,10 +403,16 @@ static void set_fb_fix(struct fb_info *fbi)
>
>        rg = &plane->fbdev->mem_desc.region[plane->idx];
>        fbi->screen_base        = rg->vaddr;
> -       mutex_lock(&fbi->mm_lock);
> -       fix->smem_start         = rg->paddr;
> -       fix->smem_len           = rg->size;
> -       mutex_unlock(&fbi->mm_lock);
> +
> +       if (!from_init) {
> +               mutex_lock(&fbi->mm_lock);
> +               fix->smem_start         = rg->paddr;
> +               fix->smem_len           = rg->size;
> +               mutex_unlock(&fbi->mm_lock);
> +       } else {
> +               fix->smem_start         = rg->paddr;
> +               fix->smem_len           = rg->size;
> +       }
>
>        fix->type = FB_TYPE_PACKED_PIXELS;
>        bpp = var->bits_per_pixel;
> @@ -704,7 +710,7 @@ static int omapfb_set_par(struct fb_info *fbi)
>        int r = 0;
>
>        omapfb_rqueue_lock(fbdev);
> -       set_fb_fix(fbi);
> +       set_fb_fix(fbi, 0);
>        r = ctrl_change_mode(fbi);
>        omapfb_rqueue_unlock(fbdev);
>
> @@ -904,7 +910,7 @@ static int omapfb_setup_mem(struct fb_info *fbi, struct omapfb_mem_info *mi)
>                if (old_size != size) {
>                        if (size) {
>                                memcpy(&fbi->var, new_var, sizeof(fbi->var));
> -                               set_fb_fix(fbi);
> +                               set_fb_fix(fbi, 0);
>                        } else {
>                                /*
>                                 * Set these explicitly to indicate that the
> @@ -1504,7 +1510,7 @@ static int fbinfo_init(struct omapfb_device *fbdev, struct fb_info *info)
>        var->bits_per_pixel = fbdev->panel->bpp;
>
>        set_fb_var(info, var);
> -       set_fb_fix(info);
> +       set_fb_fix(info, 1);
>
>        r = fb_alloc_cmap(&info->cmap, 16, 0);
>        if (r != 0)
>
> --
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Tested-by: Cory Maccarrone <darkstar6262@...il.com>

This patch works beautifully for omap850-based devices.  I need only
add a board file and LCD resolution parameters, and I get a fully
working framebuffer.

I have tested with linux-omap master (commit
6469d1c660f8751ff39836c81970cdbe46953057), adding only the board/lcd
files on HTC Herald.

- Cory
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