Subject: Re: [PATCH 01/11] drm/fb-helper: do a generic fb_setcmap helper in
 terms of crtc .gamma_set
To: linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org,
        intel-gfx@lists.freedesktop.org, nouveau@lists.freedesktop.org,
        dri-devel@lists.freedesktop.org,
        Philippe Cornu <philippe.cornu@st.com>,
        =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>,
        Yannick Fertre <yannick.fertre@st.com>,
        Gerd Hoffmann <kraxel@redhat.com>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Dave Airlie <airlied@redhat.com>,
        virtualization@lists.linux-foundation.org,
        Vincent Abriou <vincent.abriou@st.com>,
        Ben Skeggs <bskeggs@redhat.com>
References: <1497986735-14418-1-git-send-email-peda@axentia.se>
 <1497986735-14418-2-git-send-email-peda@axentia.se>
 <20170621073804.akyg4rxvoavjjt2v@phenom.ffwll.local>
From: Peter Rosin <peda@axentia.se>
Organization: Axentia Technologies AB
Message-ID: <fc8ca240-61ad-b5b6-174c-490858401237@axentia.se>
Date: Wed, 21 Jun 2017 11:40:52 +0200
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On 2017-06-21 09:38, Daniel Vetter wrote:
> On Tue, Jun 20, 2017 at 09:25:25PM +0200, Peter Rosin wrote:
>> This makes the redundant fb helpers .load_lut, .gamma_set and .gamma_get
>> totally obsolete.
>>
>> I think the gamma_store can end up invalid on error. But the way I read
>> it, that can happen in drm_mode_gamma_set_ioctl as well, so why should
>> this pesky legacy fbdev stuff be any better?
>>
>> drm_fb_helper_save_lut_atomic justs saves the gamma lut for later. However,
>> it saves it to the gamma_store which should already be up to date with what
>> .gamma_get would return and is thus a nop. So, zap it.
> 
> Removing drm_fb_helper_save_lut_atomic should be a separate patch I
> think.

Then 3 patches would be needed, first some hybrid thing that does it the
old way, but also stores the lut in .gamma_store, then the split-out that
removes drm_fb_helper_save_lut_atomic, then whatever is needed to get
to the desired code. I can certainly do that, but do you want me to?

I.e., the statement that drm_fb_helper_save_lut_atomic is a nop is only
true when (part of) the other patch is also considered.

>> Signed-off-by: Peter Rosin <peda@axentia.se>
> 
>> ---
>>  drivers/gpu/drm/drm_fb_helper.c | 131 ++++++++++++----------------------------
>>  1 file changed, 40 insertions(+), 91 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>> index 574af01..cc2d55d 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -229,22 +229,6 @@ int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
>>  }
>>  EXPORT_SYMBOL(drm_fb_helper_remove_one_connector);
>>  
>> -static void drm_fb_helper_save_lut_atomic(struct drm_crtc *crtc, struct drm_fb_helper *helper)
>> -{
>> -	uint16_t *r_base, *g_base, *b_base;
>> -	int i;
>> -
>> -	if (helper->funcs->gamma_get == NULL)
>> -		return;
>> -
>> -	r_base = crtc->gamma_store;
>> -	g_base = r_base + crtc->gamma_size;
>> -	b_base = g_base + crtc->gamma_size;
>> -
>> -	for (i = 0; i < crtc->gamma_size; i++)
>> -		helper->funcs->gamma_get(crtc, &r_base[i], &g_base[i], &b_base[i], i);
>> -}
>> -
>>  static void drm_fb_helper_restore_lut_atomic(struct drm_crtc *crtc)
>>  {
>>  	uint16_t *r_base, *g_base, *b_base;
>> @@ -285,7 +269,6 @@ int drm_fb_helper_debug_enter(struct fb_info *info)
>>  			if (drm_drv_uses_atomic_modeset(mode_set->crtc->dev))
>>  				continue;
>>  
>> -			drm_fb_helper_save_lut_atomic(mode_set->crtc, helper);
>>  			funcs->mode_set_base_atomic(mode_set->crtc,
>>  						    mode_set->fb,
>>  						    mode_set->x,
>> @@ -1167,50 +1150,6 @@ void drm_fb_helper_set_suspend_unlocked(struct drm_fb_helper *fb_helper,
>>  }
>>  EXPORT_SYMBOL(drm_fb_helper_set_suspend_unlocked);
>>  
>> -static int setcolreg(struct drm_crtc *crtc, u16 red, u16 green,
>> -		     u16 blue, u16 regno, struct fb_info *info)
>> -{
>> -	struct drm_fb_helper *fb_helper = info->par;
>> -	struct drm_framebuffer *fb = fb_helper->fb;
>> -
>> -	if (info->fix.visual == FB_VISUAL_TRUECOLOR) {
> 
> This case here seems gone, and it was also the pièce de résistance when I
> tried tackling fbdev lut support. As far as I understand this stuff we do
> not support FB_VISUAL_TRUECOLOR palette, and all that bitshifting here is
> pointless. But I'm honestly not really clear.

Oops, sorry, I simply missed that, I'll have a closer look...

> I think removing this case should also be a separate patch, and I'd very
> much prefer that someone with some fbdev-clue would ack it.
> 
>> -		u32 *palette;
>> -		u32 value;
>> -		/* place color in psuedopalette */
>> -		if (regno > 16)
>> -			return -EINVAL;
>> -		palette = (u32 *)info->pseudo_palette;
>> -		red >>= (16 - info->var.red.length);
>> -		green >>= (16 - info->var.green.length);
>> -		blue >>= (16 - info->var.blue.length);
>> -		value = (red << info->var.red.offset) |
>> -			(green << info->var.green.offset) |
>> -			(blue << info->var.blue.offset);
>> -		if (info->var.transp.length > 0) {
>> -			u32 mask = (1 << info->var.transp.length) - 1;
>> -
>> -			mask <<= info->var.transp.offset;
>> -			value |= mask;
>> -		}
>> -		palette[regno] = value;
>> -		return 0;
>> -	}
>> -
>> -	/*
>> -	 * The driver really shouldn't advertise pseudo/directcolor
>> -	 * visuals if it can't deal with the palette.
>> -	 */
>> -	if (WARN_ON(!fb_helper->funcs->gamma_set ||
>> -		    !fb_helper->funcs->gamma_get))
>> -		return -EINVAL;
>> -
>> -	WARN_ON(fb->format->cpp[0] != 1);
>> -
>> -	fb_helper->funcs->gamma_set(crtc, red, green, blue, regno);
>> -
>> -	return 0;
>> -}
>> -
>>  /**
>>   * drm_fb_helper_setcmap - implementation for &fb_ops.fb_setcmap
>>   * @cmap: cmap to set
>> @@ -1220,51 +1159,61 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
>>  {
>>  	struct drm_fb_helper *fb_helper = info->par;
>>  	struct drm_device *dev = fb_helper->dev;
>> -	const struct drm_crtc_helper_funcs *crtc_funcs;
>> -	u16 *red, *green, *blue, *transp;
>> +	struct drm_modeset_acquire_ctx ctx;
>>  	struct drm_crtc *crtc;
>> -	int i, j, rc = 0;
>> -	int start;
>> +	u16 *r, *g, *b;
>> +	int i, ret;
>>  
>>  	if (oops_in_progress)
>>  		return -EBUSY;
>>  
>> -	drm_modeset_lock_all(dev);
>> +	if (cmap->start + cmap->len < cmap->start)
>> +		return -EINVAL;
>> +
>> +	drm_modeset_acquire_init(&ctx, 0);
>> +retry:
>> +	ret = drm_modeset_lock_all_ctx(dev, &ctx);
>> +	if (ret)
>> +		goto out;
>>  	if (!drm_fb_helper_is_bound(fb_helper)) {
>> -		drm_modeset_unlock_all(dev);
>> -		return -EBUSY;
>> +		ret = -EBUSY;
>> +		goto out;
>>  	}
>>  
>>  	for (i = 0; i < fb_helper->crtc_count; i++) {
>>  		crtc = fb_helper->crtc_info[i].mode_set.crtc;
>> -		crtc_funcs = crtc->helper_private;
>> -
>> -		red = cmap->red;
>> -		green = cmap->green;
>> -		blue = cmap->blue;
>> -		transp = cmap->transp;
>> -		start = cmap->start;
>> +		if (!crtc->funcs->gamma_set || !crtc->gamma_size) {
>> +			ret = -EINVAL;
>> +			goto out;
>> +		}
>>  
>> -		for (j = 0; j < cmap->len; j++) {
>> -			u16 hred, hgreen, hblue, htransp = 0xffff;
>> +		if (cmap->start + cmap->len > crtc->gamma_size) {
>> +			ret = -EINVAL;
>> +			goto out;
>> +		}
>>  
>> -			hred = *red++;
>> -			hgreen = *green++;
>> -			hblue = *blue++;
>> +		r = crtc->gamma_store;
>> +		g = r + crtc->gamma_size;
>> +		b = g + crtc->gamma_size;
>>  
>> -			if (transp)
>> -				htransp = *transp++;
>> +		memcpy(r + cmap->start, cmap->red, cmap->len * sizeof(u16));
>> +		memcpy(g + cmap->start, cmap->green, cmap->len * sizeof(u16));
>> +		memcpy(b + cmap->start, cmap->blue, cmap->len * sizeof(u16));
>>  
>> -			rc = setcolreg(crtc, hred, hgreen, hblue, start++, info);
>> -			if (rc)
>> -				goto out;
>> -		}
>> -		if (crtc_funcs->load_lut)
>> -			crtc_funcs->load_lut(crtc);
>> +		ret = crtc->funcs->gamma_set(crtc, r, g, b,
>> +					     crtc->gamma_size, &ctx);
>> +		if (ret)
>> +			break;
>>  	}
>> - out:
>> -	drm_modeset_unlock_all(dev);
>> -	return rc;
>> +out:
>> +	if (ret == -EDEADLK) {
>> +		drm_modeset_backoff(&ctx);
>> +		goto retry;
>> +	}
>> +	drm_modeset_drop_locks(&ctx);
>> +	drm_modeset_acquire_fini(&ctx);
>> +
>> +	return ret;
> 
> It's a pre-existing bug, but should we also try to restore the fbdev lut
> in drm_fb_helper_restore_fbdev_mode_unlocked()? Would be yet another bug,
> but might be relevant for your use-case. Just try to run both an fbdev
> application and some kms-native thing, and then SIGKILL the native kms
> app.
> 
> But since pre-existing not really required, and probably too much effort.

Good thing too, because I don't really know my way around this code...

Cheers,
peda

> Thanks, Daniel
> 
>>  }
>>  EXPORT_SYMBOL(drm_fb_helper_setcmap);
>>  
>> -- 
>> 2.1.4
>>
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