From nobody Wed Oct 1 23:30:05 2025 Received: from smtpout-04.galae.net (smtpout-04.galae.net [185.171.202.116]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5A7FF2D542F for ; Fri, 26 Sep 2025 16:35:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.171.202.116 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758904513; cv=none; b=TAAvLayb+4L77jDC0f+lXPxop/ZODP1FCtudp0JGtCWgjJIMjoV47HgqBhS2dgXN1uP5It7Su07TlUb48II/mZD+zQXKt9SRBLn9p1EWZa40RoQYUqFN77bkJmoTJvVeL4zFoYF0er3YAqyBM07c4fnhZboDKUf+xIktW4lUs48= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758904513; c=relaxed/simple; bh=NQkO9sERJ5k+kSkZyB8VfhDtTdRQ4XwjrisUwBVDo+U=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Tl/K8WV3J1ew0KG5G9coTA0Jk9rkXYEuMXwtE0bEJQ9DRKrlW7HvEfAnGIdxzofoCmSxN5XEvk0fBlUGbLElTL7OAbB0Zq9Uzq6tnExCo6gxL5T4gOudje1r6eQBopeo7dT8ExCci+AhVTYm/rd8aQDMbWAnWohHhJOmhztpjz0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=L1atmfeB; arc=none smtp.client-ip=185.171.202.116 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="L1atmfeB" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-04.galae.net (Postfix) with ESMTPS id 27D28C00D98; Fri, 26 Sep 2025 16:34:52 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 85F1D606B5; Fri, 26 Sep 2025 16:35:09 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id B0B56102F1829; Fri, 26 Sep 2025 18:35:06 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1758904508; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=ICzSvLvJb7esyCKXOeOL5sJVQ8upayrrtyMxyExJw7M=; b=L1atmfeBiDc6ktznLNxQbLAPCdAs2qwzkmXmYL+F1kKNRUOxRYYki4LKTc32XRi+Y2/zMn eAljRYkPA9LVeWDK3HG7JvDAaLy5jsZ1xnWwRChVy3RRUq88NpFKhysLHXkKMjXtv2yY1h WoPjpNrnuM7Izs7DDepPGLm6Hpcn4T2MsClHITKghBWIRmMMToqCV82k8MFTM8/q+m3Sms 0EmEBpeA+DRggKp/c2WD43BNwigbcXlA0CkYHpjUlh77U2zq2YMo+tHzenq2fXUt/AsqRZ rSpgEkJN9zE4tgtijaUN2WrvbH6gpIyFNPwIl09uF0S+QGEbB/e1qv4hFYYFXA== From: Luca Ceresoli Date: Fri, 26 Sep 2025 18:33:28 +0200 Subject: [PATCH v2 2/2] drm/bridge: ti-sn65dsi83: protect device resources on unplug Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250926-drm-bridge-atomic-vs-remove-v2-2-69f7d5ca1a92@bootlin.com> References: <20250926-drm-bridge-atomic-vs-remove-v2-0-69f7d5ca1a92@bootlin.com> In-Reply-To: <20250926-drm-bridge-atomic-vs-remove-v2-0-69f7d5ca1a92@bootlin.com> To: Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter Cc: Hui Pu , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Luca Ceresoli , Dmitry Baryshkov X-Mailer: b4 0.14.2 X-Last-TLS-Session-Version: TLSv1.3 To support hot-unplug of this bridge we need to protect access to device resources in case sn65dsi83_remove() happens concurrently to other code. Some care is needed for the case when the unplug happens before sn65dsi83_atomic_disable() has a chance to enter the critical section (i.e. a successful drm_bridge_enter() call), which occurs whenever the hardware is removed while the display is active. When that happens, sn65dsi83_atomic_disable() in unable to release the resources taken by sn65dsi83_atomic_pre_enable(). To ensure those resources are released exactly once on device removal: * move the code to release them to a dedicated function * register that function when the resources are taken in sn65dsi83_atomic_pre_enable() * if sn65dsi83_atomic_disable() happens before sn65dsi83_remove() (typical non-hot-unplug case): * sn65dsi83_atomic_disable() can enter the critical section (drm_bridge_enter() returns 0) -> it releases and executes the devres action * if sn65dsi83_atomic_disable() happens after sn65dsi83_remove() (typical hot-unplug case): * sn65dsi83_remove() -> drm_bridge_unplug() prevents sn65dsi83_atomic_disable() from entering the critical section (drm_bridge_enter() returns nonzero), so sn65dsi83_atomic_disable() cannot release and execute the devres action * the devres action is executed at the end of sn65dsi83_remove() Signed-off-by: Luca Ceresoli --- Changed in v2: - Use a devres action instead of a flag --- drivers/gpu/drm/bridge/ti-sn65dsi83.c | 85 ++++++++++++++++++++++++++++---= ---- 1 file changed, 68 insertions(+), 17 deletions(-) diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge= /ti-sn65dsi83.c index 033c44326552ab167d4e8d9b74957c585e4c6fb7..92014366449237668b50cc884a6= 7f52fcd5777c3 100644 --- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c +++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c @@ -406,6 +406,10 @@ static void sn65dsi83_reset_work(struct work_struct *w= s) { struct sn65dsi83 *ctx =3D container_of(ws, struct sn65dsi83, reset_work); int ret; + int idx; + + if (!drm_bridge_enter(&ctx->bridge, &idx)) + return; =20 /* Reset the pipe */ ret =3D sn65dsi83_reset_pipe(ctx); @@ -415,12 +419,18 @@ static void sn65dsi83_reset_work(struct work_struct *= ws) } if (ctx->irq) enable_irq(ctx->irq); + + drm_bridge_exit(idx); } =20 static void sn65dsi83_handle_errors(struct sn65dsi83 *ctx) { unsigned int irq_stat; int ret; + int idx; + + if (!drm_bridge_enter(&ctx->bridge, &idx)) + return; =20 /* * Schedule a reset in case of: @@ -441,6 +451,8 @@ static void sn65dsi83_handle_errors(struct sn65dsi83 *c= tx) =20 schedule_work(&ctx->reset_work); } + + drm_bridge_exit(idx); } =20 static void sn65dsi83_monitor_work(struct work_struct *work) @@ -463,6 +475,40 @@ static void sn65dsi83_monitor_stop(struct sn65dsi83 *c= tx) cancel_delayed_work_sync(&ctx->monitor_work); } =20 +/* + * Release resources taken by sn65dsi83_atomic_pre_enable(). + * + * Normally invoked by sn65dsi83_atomic_disable(). But if + * sn65dsi83_remove() is invoked while enabled, then drm_bridge_unplug() + * would defuse sn65dsi83_atomic_disable(). Thus a devres action is used to + * ensure exactly one code path (removal or atomic disable) invokes this + * code. + */ +static void sn65dsi83_release_resources(void *data) +{ + struct sn65dsi83 *ctx =3D (struct sn65dsi83 *)data; + int ret; + + if (ctx->irq) { + /* Disable irq */ + regmap_write(ctx->regmap, REG_IRQ_EN, 0x0); + regmap_write(ctx->regmap, REG_IRQ_GLOBAL, 0x0); + } else { + /* Stop the polling task */ + sn65dsi83_monitor_stop(ctx); + } + + /* Put the chip in reset, pull EN line low, and assure 10ms reset low tim= ing. */ + gpiod_set_value_cansleep(ctx->enable_gpio, 0); + usleep_range(10000, 11000); + + ret =3D regulator_disable(ctx->vcc); + if (ret) + dev_err(ctx->dev, "Failed to disable vcc: %d\n", ret); + + regcache_mark_dirty(ctx->regmap); +} + static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge, struct drm_atomic_state *state) { @@ -478,10 +524,15 @@ static void sn65dsi83_atomic_pre_enable(struct drm_br= idge *bridge, __le16 le16val; u16 val; int ret; + int idx; + + if (!drm_bridge_enter(bridge, &idx)) + return; =20 ret =3D regulator_enable(ctx->vcc); if (ret) { dev_err(ctx->dev, "Failed to enable vcc: %d\n", ret); + drm_bridge_exit(idx); return; } =20 @@ -625,6 +676,8 @@ static void sn65dsi83_atomic_pre_enable(struct drm_brid= ge *bridge, dev_err(ctx->dev, "failed to lock PLL, ret=3D%i\n", ret); /* On failure, disable PLL again and exit. */ regmap_write(ctx->regmap, REG_RC_PLL_EN, 0x00); + devm_add_action(ctx->dev, sn65dsi83_release_resources, ctx); + drm_bridge_exit(idx); return; } =20 @@ -633,6 +686,9 @@ static void sn65dsi83_atomic_pre_enable(struct drm_brid= ge *bridge, =20 /* Wait for 10ms after soft reset as specified in datasheet */ usleep_range(10000, 12000); + + devm_add_action(ctx->dev, sn65dsi83_release_resources, ctx); + drm_bridge_exit(idx); } =20 static void sn65dsi83_atomic_enable(struct drm_bridge *bridge, @@ -640,6 +696,10 @@ static void sn65dsi83_atomic_enable(struct drm_bridge = *bridge, { struct sn65dsi83 *ctx =3D bridge_to_sn65dsi83(bridge); unsigned int pval; + int idx; + + if (!drm_bridge_enter(bridge, &idx)) + return; =20 /* Clear all errors that got asserted during initialization. */ regmap_read(ctx->regmap, REG_IRQ_STAT, &pval); @@ -659,32 +719,22 @@ static void sn65dsi83_atomic_enable(struct drm_bridge= *bridge, /* Use the polling task */ sn65dsi83_monitor_start(ctx); } + + drm_bridge_exit(idx); } =20 static void sn65dsi83_atomic_disable(struct drm_bridge *bridge, struct drm_atomic_state *state) { struct sn65dsi83 *ctx =3D bridge_to_sn65dsi83(bridge); - int ret; - - if (ctx->irq) { - /* Disable irq */ - regmap_write(ctx->regmap, REG_IRQ_EN, 0x0); - regmap_write(ctx->regmap, REG_IRQ_GLOBAL, 0x0); - } else { - /* Stop the polling task */ - sn65dsi83_monitor_stop(ctx); - } + int idx; =20 - /* Put the chip in reset, pull EN line low, and assure 10ms reset low tim= ing. */ - gpiod_set_value_cansleep(ctx->enable_gpio, 0); - usleep_range(10000, 11000); + if (!drm_bridge_enter(bridge, &idx)) + return; =20 - ret =3D regulator_disable(ctx->vcc); - if (ret) - dev_err(ctx->dev, "Failed to disable vcc: %d\n", ret); + devm_release_action(ctx->dev, sn65dsi83_release_resources, ctx); =20 - regcache_mark_dirty(ctx->regmap); + drm_bridge_exit(idx); } =20 static enum drm_mode_status @@ -1005,6 +1055,7 @@ static void sn65dsi83_remove(struct i2c_client *clien= t) { struct sn65dsi83 *ctx =3D i2c_get_clientdata(client); =20 + drm_bridge_unplug(&ctx->bridge); drm_bridge_remove(&ctx->bridge); } =20 --=20 2.51.0