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Thu, 20 Aug 2026 06:54:11 +0000 Message-ID: Date: Thu, 20 Aug 2026 08:54:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/6] drm: Add drm_timeout_rel_to_jiffies() To: =?UTF-8?Q?Ma=C3=ADra_Canal?= , Maarten Lankhorst , Maxime Ripard , David Airlie , Simona Vetter , Alex Deucher , =?UTF-8?Q?Christian_K=C3=B6nig?= , Melissa Wen , Iago Toral , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Dave Stevenson , Raspberry Pi Kernel Maintenance Cc: kernel-dev@igalia.com, dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, intel-gfx@lists.freedesktop.org References: <20260817-drm-timeout-helpers-v2-0-73052b669f49@igalia.com> <20260817-drm-timeout-helpers-v2-2-73052b669f49@igalia.com> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNJ1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPsLAjgQTAQgAOAIb AwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftODH AAoJEGgNwR1TC3ojx1wH/0hKGWugiqDgLNXLRD/4TfHBEKmxIrmfu9Z5t7vwUKfwhFL6hqvo lXPJJKQpQ2z8+X2vZm/slsLn7J1yjrOsoJhKABDi+3QWWSGkaGwRJAdPVVyJMfJRNNNIKwVb U6B1BkX2XDKDGffF4TxlOpSQzdtNI/9gleOoUA8+jy8knnDYzjBNOZqLG2FuTdicBXblz0Mf vg41gd9kCwYXDnD91rJU8tzylXv03E75NCaTxTM+FBXPmsAVYQ4GYhhgFt8S2UWMoaaABLDe 7l5FdnLdDEcbmd8uLU2CaG4W2cLrUaI4jz2XbkcPQkqTQ3EB67hYkjiEE6Zy3ggOitiQGcqp j//OwE0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRHUE9eosYb T6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgTRjP+qbU6 3Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+RdhgATnWW GKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zbehDda8lv hFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r12+lqdsA EQEAAcLAdgQYAQgAIAIbDBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftOH6AAoJEGgNwR1T C3ojVSkIALpAPkIJPQoURPb1VWjh34l0HlglmYHvZszJWTXYwavHR8+k6Baa6H7ufXNQtThR yIxJrQLW6rV5lm7TjhffEhxVCn37+cg0zZ3j7zIsSS0rx/aMwi6VhFJA5hfn3T0TtrijKP4A SAQO9xD1Zk9/61JWk8OysuIh7MXkl0fxbRKWE93XeQBhIJHQfnc+YBLprdnxR446Sh8Wn/2D Ya8cavuWf2zrB6cZurs048xe0UbSW5AOSo4V9M0jzYI4nZqTmPxYyXbm30Kvmz0rYVRaitYJ 4kyYYMhuULvrJDMjZRvaNe52tkKAvMevcGdt38H4KSVXAylqyQOW5zvPc4/sq9c= In-Reply-To: <20260817-drm-timeout-helpers-v2-2-73052b669f49@igalia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: 638CF84F15 X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; FREEMAIL_TO(0.00)[igalia.com,linux.intel.com,kernel.org,gmail.com,ffwll.ch,amd.com,intel.com,raspberrypi.com]; RCPT_COUNT_TWELVE(0.00)[19]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[igalia.com:email, suse.com:url, suse.de:mid, suse.de:dkim, imap1.dmz-prg2.suse.org:helo, imap1.dmz-prg2.suse.org:rdns] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Hi Am 17.08.26 um 23:05 schrieb Maíra Canal: > drm_timeout_abs_to_jiffies() covers the drivers whose wait UAPI takes an > absolute deadline, but there is no equivalent for the drivers that > express a wait as a duration. Drivers such as i915 and v3d convert the > value themselves. > > Converting a nanosecond duration to jiffies needs some care. > nsecs_to_jiffies() returns unsigned long, so on 32-bit a large > userspace-supplied timeout overflows its range and is silently truncated. > > i915 already handles both cases in a local helper, which v3d has a copy > of. Add the same conversion to the core, so that it is available to any > driver and both copies can be dropped. > > Signed-off-by: Maíra Canal > --- > drivers/gpu/drm/drm_timeout.c | 34 ++++++++++++++++++++++++++++++++++ > include/drm/drm_utils.h | 1 + > 2 files changed, 35 insertions(+) > > diff --git a/drivers/gpu/drm/drm_timeout.c b/drivers/gpu/drm/drm_timeout.c > index 78e9f65e5477..18c2719d1fe9 100644 > --- a/drivers/gpu/drm/drm_timeout.c > +++ b/drivers/gpu/drm/drm_timeout.c > @@ -9,6 +9,7 @@ > #include > #include > #include > +#include > #include > > #include > @@ -45,3 +46,36 @@ signed long drm_timeout_abs_to_jiffies(int64_t timeout_nsec) > return timeout_jiffies64 + 1; > } > EXPORT_SYMBOL(drm_timeout_abs_to_jiffies); > + > +/** > + * drm_timeout_rel_to_jiffies - calculate jiffies timeout from relative value > + * > + * @timeout_nsec: relative timeout in ns, 0 for poll > + * > + * Calculate the timeout in jiffies from a relative timeout in ns, for drivers > + * whose UAPI expresses a wait as a duration rather than as a deadline. > + * > + * The result is clamped to MAX_JIFFY_OFFSET. That keeps it positive once it is > + * converted to the signed long taken by dma_fence_wait_timeout() and friends, > + * which matters on 32-bit, and keeps it distinct from MAX_SCHEDULE_TIMEOUT so > + * that a finite wait is never understood as an infinite one. > + * > + * It's strongly discouraged to use relative timeouts in uAPIs, as they do not > + * survive a restarted ioctl. A signal-interrupted ioctl is re-entered with the > + * same arguments, so the duration starts counting from zero again. New uAPIs > + * should take an absolute deadline and use drm_timeout_abs_to_jiffies(). I would not speak of uAPIs here, as it's unrelated to the function at hand. You might want to mention it in the commit description though. Please also see my comments on the docs of drm_timeout_abs_to_jiffies(). Most of it applies here as well. Best regards Thomas > + */ > +unsigned long drm_timeout_rel_to_jiffies(u64 timeout_nsec) > +{ > + /* make 0 timeout means poll, as for the absolute variant */ > + if (timeout_nsec == 0) > + return 0; > + > + /* nsecs_to_jiffies64() does not guard against overflow */ > + if ((NSEC_PER_SEC % HZ) != 0 && > + div_u64(timeout_nsec, NSEC_PER_SEC) >= MAX_JIFFY_OFFSET / HZ) > + return MAX_JIFFY_OFFSET; > + > + return min_t(u64, MAX_JIFFY_OFFSET, nsecs_to_jiffies64(timeout_nsec) + 1); > +} > +EXPORT_SYMBOL(drm_timeout_rel_to_jiffies); > diff --git a/include/drm/drm_utils.h b/include/drm/drm_utils.h > index 6a46f755daba..8c0cc9835413 100644 > --- a/include/drm/drm_utils.h > +++ b/include/drm/drm_utils.h > @@ -25,5 +25,6 @@ const struct drm_panel_backlight_quirk * > drm_get_panel_backlight_quirk(const struct drm_edid *edid); > > signed long drm_timeout_abs_to_jiffies(int64_t timeout_nsec); > +unsigned long drm_timeout_rel_to_jiffies(u64 timeout_nsec); > > #endif > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)