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Mon, 18 Mar 2024 08:19:10 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap1.dmz-prg2.suse.org with ESMTPSA id l05SAP7492XkMwAAD6G6ig (envelope-from ); Mon, 18 Mar 2024 08:19:10 +0000 Message-ID: <4eea339c-48b0-416e-90a5-87f90ea5bf1d@suse.de> Date: Mon, 18 Mar 2024 09:19:09 +0100 Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/43] drm/fbdev-generic: Do not set physical framebuffer address Content-Language: en-US To: Javier Martinez Canillas , daniel@ffwll.ch, airlied@gmail.com, deller@gmx.de Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Zack Rusin , Maarten Lankhorst , Maxime Ripard , stable@vger.kernel.org References: <20240312154834.26178-1-tzimmermann@suse.de> <20240312154834.26178-2-tzimmermann@suse.de> <87a5mxgha0.fsf@minerva.mail-host-address-is-not-set> From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Authentication-Results: smtp-out1.suse.de; none X-Spam-Level: X-Spam-Score: -4.29 X-Spamd-Result: default: False [-4.29 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; XM_UA_NO_VERSION(0.01)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com,gmx.de]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; NEURAL_HAM_LONG(-1.00)[-1.000]; BAYES_HAM(-3.00)[100.00%]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; RCPT_COUNT_SEVEN(0.00)[10]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,vmware.com:email,intel.com:email,bootlin.com:url]; FREEMAIL_TO(0.00)[redhat.com,ffwll.ch,gmail.com,gmx.de]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[] X-Spam-Flag: NO Hi Am 17.03.24 um 13:43 schrieb Javier Martinez Canillas: > Thomas Zimmermann writes: > > Hello Thomas, > >> Framebuffer memory is allocated via vmalloc() from non-contiguous > It's vmalloc() true, but through vzmalloc() so I would mention that > function instead in the commit message. Ok. > >> physical pages. The physical framebuffer start address is therefore >> meaningless. Do not set it. >> >> The value is not used within the kernel and only exported to userspace >> on dedicated ARM configs. No functional change is expected. >> > How's that info used? Does user-space assumes that the whole memory range > is contiguous in physical memory or just cares about the phyisical start > address ? I assume that it is supposed to refer to contiguous memory. There's the corresponding field smem_len, which refers to the full memory. > >> Signed-off-by: Thomas Zimmermann >> Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering") >> Cc: Thomas Zimmermann >> Cc: Javier Martinez Canillas >> Cc: Zack Rusin >> Cc: Maarten Lankhorst >> Cc: Maxime Ripard >> Cc: # v6.4+ >> --- >> drivers/gpu/drm/drm_fbdev_generic.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c >> index d647d89764cb9..b4659cd6285ab 100644 >> --- a/drivers/gpu/drm/drm_fbdev_generic.c >> +++ b/drivers/gpu/drm/drm_fbdev_generic.c >> @@ -113,7 +113,6 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper, >> /* screen */ >> info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST; >> info->screen_buffer = screen_buffer; >> - info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer)); >> info->fix.smem_len = screen_size; >> > Makes sense: > > Reviewed-by: Javier Martinez Canillas > > What about drivers/gpu/drm/drm_fb_helper.c btw? Since the memory range > allocated may not be physically contiguous if a platform uses an IOMMU ? > > Asking because I don't really know how these exported values are used... > I just know that is when the CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM is enabled. The value of smem_start is used in the fbdev code in only two places : deferred I/O [1] and devfile I/O [2]. For the former, patch 5 of this series adds an additional test. The latter case is only relevant for framebuffers in I/O memory space. But that does not affect fbdev-generic, which has the shadow buffer in main memory. Some driver-internal fbdev code sets smem_length, such as in gma500, but these drivers are special anyway. For what userspace does with this value IDK. But it can't be much, as we've had smem_start cleared for years. Best regards Thomas [1] https://elixir.bootlin.com/linux/v6.8/source/drivers/video/fbdev/core/fb_defio.c#L34 [2] https://elixir.bootlin.com/linux/v6.8/source/drivers/video/fbdev/core/fb_io_fops.c#L143 > > -- > Best regards, > > Javier Martinez Canillas > Core Platforms > Red Hat > > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)