From: Joerg Roedel <joro@8bytes.org>
To: Rob Clark <robdclark@gmail.com>
Cc: Rob Clark <robdclark@chromium.org>,
aarch64-laptops@lists.linaro.org,
Ulf Hansson <ulf.hansson@linaro.org>,
Heikki Krogerus <heikki.krogerus@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Bartosz Golaszewski <brgl@bgdev.pl>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
iommu@lists.linux-foundation.org,
Sudeep Holla <sudeep.holla@arm.com>,
Joe Perches <joe@perches.com>
Subject: Re: [PATCH 1/2] iommu: add support for drivers that manage iommu explicitly
Date: Thu, 4 Jul 2019 10:20:01 +0200 [thread overview]
Message-ID: <20190704082001.GD6546@8bytes.org> (raw)
In-Reply-To: <20190702202631.32148-2-robdclark@gmail.com>
Hi Rob,
On Tue, Jul 02, 2019 at 01:26:18PM -0700, Rob Clark wrote:
> 1) In some cases the bootloader takes the iommu out of bypass and
> enables the display. This is in particular a problem on the aarch64
> laptops that exist these days, and modern snapdragon android devices.
> (Older devices also enabled the display in bootloader but did not
> take the iommu out of bypass.) Attaching a DMA or IDENTITY domain
> while scanout is active, before the driver has a chance to intervene,
> makes things go *boom*
Just to make sure I get this right: The bootloader inializes the SMMU
and creates non-identity mappings for the GPU? And when the SMMU driver
in Linux takes over this breaks display output.
> + /*
> + * If driver is going to manage iommu directly, then avoid
> + * attaching any non driver managed domain. There could
> + * be already active dma underway (ie. scanout in case of
> + * bootloader enabled display), and interfering with that
> + * will make things go *boom*
> + */
> + if ((domain->type != IOMMU_DOMAIN_UNMANAGED) &&
> + dev->driver && dev->driver->driver_manages_iommu)
> + return 0;
> +
When the default domain is attached, there is usually no driver attached
yet. I think this needs to be communicated by the firmware to Linux and
the code should check against that.
> - bool suppress_bind_attrs; /* disables bind/unbind via sysfs */
> + bool suppress_bind_attrs:1; /* disables bind/unbind via sysfs */
> + bool driver_manages_iommu:1; /* driver manages IOMMU explicitly */
How does this field get set?
Joerg
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WARNING: multiple messages have this Message-ID (diff)
From: Joerg Roedel <joro@8bytes.org>
To: Rob Clark <robdclark@gmail.com>
Cc: iommu@lists.linux-foundation.org,
dri-devel@lists.freedesktop.org,
aarch64-laptops@lists.linaro.org,
Jordan Crouse <jcrouse@codeaurora.org>,
Rob Clark <robdclark@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Ulf Hansson <ulf.hansson@linaro.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Heikki Krogerus <heikki.krogerus@linux.intel.com>,
Vivek Gautam <vivek.gautam@codeaurora.org>,
Bartosz Golaszewski <brgl@bgdev.pl>,
Joe Perches <joe@perches.com>,
Sudeep Holla <sudeep.holla@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] iommu: add support for drivers that manage iommu explicitly
Date: Thu, 4 Jul 2019 10:20:01 +0200 [thread overview]
Message-ID: <20190704082001.GD6546@8bytes.org> (raw)
In-Reply-To: <20190702202631.32148-2-robdclark@gmail.com>
Hi Rob,
On Tue, Jul 02, 2019 at 01:26:18PM -0700, Rob Clark wrote:
> 1) In some cases the bootloader takes the iommu out of bypass and
> enables the display. This is in particular a problem on the aarch64
> laptops that exist these days, and modern snapdragon android devices.
> (Older devices also enabled the display in bootloader but did not
> take the iommu out of bypass.) Attaching a DMA or IDENTITY domain
> while scanout is active, before the driver has a chance to intervene,
> makes things go *boom*
Just to make sure I get this right: The bootloader inializes the SMMU
and creates non-identity mappings for the GPU? And when the SMMU driver
in Linux takes over this breaks display output.
> + /*
> + * If driver is going to manage iommu directly, then avoid
> + * attaching any non driver managed domain. There could
> + * be already active dma underway (ie. scanout in case of
> + * bootloader enabled display), and interfering with that
> + * will make things go *boom*
> + */
> + if ((domain->type != IOMMU_DOMAIN_UNMANAGED) &&
> + dev->driver && dev->driver->driver_manages_iommu)
> + return 0;
> +
When the default domain is attached, there is usually no driver attached
yet. I think this needs to be communicated by the firmware to Linux and
the code should check against that.
> - bool suppress_bind_attrs; /* disables bind/unbind via sysfs */
> + bool suppress_bind_attrs:1; /* disables bind/unbind via sysfs */
> + bool driver_manages_iommu:1; /* driver manages IOMMU explicitly */
How does this field get set?
Joerg
next prev parent reply other threads:[~2019-07-04 8:20 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-02 20:26 [PATCH 0/2] iommu: handle drivers that manage iommu directly Rob Clark
2019-07-02 20:26 ` Rob Clark
2019-07-02 20:26 ` Rob Clark
2019-07-02 20:26 ` [PATCH 1/2] iommu: add support for drivers that manage iommu explicitly Rob Clark
2019-07-02 20:26 ` Rob Clark
2019-07-02 20:26 ` Rob Clark
2019-07-03 12:42 ` Robin Murphy
2019-07-03 12:42 ` Robin Murphy
2019-07-03 14:18 ` Rob Clark
2019-07-03 14:18 ` Rob Clark
2019-07-04 8:20 ` Joerg Roedel [this message]
2019-07-04 8:20 ` Joerg Roedel
2019-07-04 13:51 ` Rob Clark
2019-07-04 13:51 ` Rob Clark
2019-07-04 13:51 ` Rob Clark
2019-07-10 18:28 ` [PATCH v2] " Rob Clark
2019-07-10 18:28 ` Rob Clark
2019-07-10 18:28 ` Rob Clark
2019-07-22 14:28 ` Joerg Roedel
2019-07-22 14:28 ` Joerg Roedel
2019-07-22 14:28 ` Joerg Roedel
2019-07-22 15:41 ` Rob Clark
2019-07-22 15:41 ` Rob Clark
2019-07-22 15:41 ` Rob Clark
2019-07-22 15:48 ` Joerg Roedel
2019-07-22 15:48 ` Joerg Roedel
2019-07-22 15:48 ` Joerg Roedel
2019-07-22 16:23 ` Rob Clark
2019-07-22 16:23 ` Rob Clark
2019-07-22 16:23 ` Rob Clark
2019-07-23 15:38 ` Will Deacon
2019-07-23 15:38 ` Will Deacon
2019-07-23 15:38 ` Will Deacon
2019-07-23 17:40 ` Rob Clark
2019-07-23 17:40 ` Rob Clark
2019-07-23 17:40 ` Rob Clark
2019-07-24 10:51 ` Will Deacon
2019-07-24 10:51 ` Will Deacon
2019-07-24 10:51 ` Will Deacon
2019-07-24 16:11 ` Rob Clark
2019-07-24 16:11 ` Rob Clark
2019-07-24 16:11 ` Rob Clark
2019-07-02 20:26 ` [PATCH 2/2] drm/msm: mark devices where iommu is managed by driver Rob Clark
2019-07-02 20:26 ` Rob Clark
2019-07-02 20:26 ` Rob Clark
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