[PATCH] drm/fbdev: Clamp fbdev surface size if too large

[Thomas Zimmermann]

Hi

Am 04.10.21 um 10:23 schrieb Ville Syrjälä:
> On Mon, Oct 04, 2021 at 10:15:06AM +0200, Thomas Zimmermann wrote:
>> Clamp the fbdev surface size of the available maximum height to avoid
>> failing to init console emulation. An example error is shown below.
>>
>>    bad framebuffer height 2304, should be >= 768 && <= 768
>>    [drm] Initialized simpledrm 1.0.0 20200625 for simple-framebuffer.0 on minor 0
>>    simple-framebuffer simple-framebuffer.0: [drm] *ERROR* fbdev: Failed to setup generic emulation (ret=-22)
>>
>> This is especially a problem with drivers that have very small screen
>> sizes and cannot over-allocate at all.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>> Fixes: 11e8f5fd223b ("drm: Add simpledrm driver")
>> Reported-by: Amanoel Dawod <kernel at amanoeldawod.com>
>> Reported-by: Zoltán Kővágó <dirty.ice.hu at gmail.com>
>> Reported-by: Michael Stapelberg <michael+lkml at stapelberg.ch>
>> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
>> Cc: Maxime Ripard <maxime at cerno.tech>
>> Cc: dri-devel at lists.freedesktop.org
>> Cc: <stable at vger.kernel.org> # v5.14+
>> ---
>>   drivers/gpu/drm/drm_fb_helper.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>> index 6860223f0068..364f11900b37 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -1508,6 +1508,7 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
>>   {
>>   	struct drm_client_dev *client = &fb_helper->client;
>>   	struct drm_device *dev = fb_helper->dev;
>> +	struct drm_mode_config *config = &dev->mode_config;
>>   	int ret = 0;
>>   	int crtc_count = 0;
>>   	struct drm_connector_list_iter conn_iter;
>> @@ -1665,6 +1666,11 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
>>   	/* Handle our overallocation */
>>   	sizes.surface_height *= drm_fbdev_overalloc;
>>   	sizes.surface_height /= 100;
>> +	if (sizes.surface_height > config->max_height) {
>> +		drm_warn(dev, "Fbdev over-allocation too large; clamping height to %d\n",
>> +			 config->max_height);
> 
> drm_warn() seems a bit excessive. drm_info()?
> 
> Or could just have no printk and use a simple min() perhaps.

The framebuffer code uses debug_kms for this kind of message. I guess, 
I'll go with that.

Best regards
Thamas

> 
>> +		sizes.surface_height = config->max_height;
>> +	}
>>
>>   	/* push down into drivers */
>>   	ret = (*fb_helper->funcs->fb_probe)(fb_helper, &sizes);
>> --
>> 2.33.0
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
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