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From: Dmitry Osipenko <digetx@gmail.com>
To: Nicolin Chen <nicoleotsuka@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>,
	joro@8bytes.org, krzk@kernel.org, vdumpa@nvidia.com,
	jonathanh@nvidia.com, linux-tegra@vger.kernel.org,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and .attach_dev
Date: Fri, 2 Oct 2020 04:55:34 +0300	[thread overview]
Message-ID: <1b621b9d-cdc3-c7aa-2fa2-d728ae2bbc5d@gmail.com> (raw)
In-Reply-To: <20201002010751.GA26971@Asurada-Nvidia>

02.10.2020 04:07, Nicolin Chen пишет:
> On Thu, Oct 01, 2020 at 11:33:38PM +0300, Dmitry Osipenko wrote:
>>>>> If we can't come to an agreement on globalizing mc pointer, would
>>>>> it be possible to pass tegra_mc_driver through tegra_smmu_probe()
>>>>> so we can continue to use driver_find_device_by_fwnode() as v1?
>>>>>
>>>>> v1: https://lkml.org/lkml/2020/9/26/68
>>>>
>>>> tegra_smmu_probe() already takes a struct tegra_mc *. Did you mean
>>>> tegra_smmu_probe_device()? I don't think we can do that because it isn't
>>>
>>> I was saying to have a global parent_driver pointer: similar to
>>> my v1, yet rather than "extern" the tegra_mc_driver, we pass it
>>> through egra_smmu_probe() and store it in a static global value
>>> so as to call tegra_smmu_get_by_fwnode() in ->probe_device().
>>>
>>> Though I agree that creating a global device pointer (mc) might
>>> be controversial, yet having a global parent_driver pointer may
>>> not be against the rule, considering that it is common in iommu
>>> drivers to call driver_find_device_by_fwnode in probe_device().
>>
>> You don't need the global pointer if you have SMMU OF node.
>>
>> You could also get driver pointer from mc->dev->driver.
>>
>> But I don't think you need to do this at all. The probe_device() could
>> be invoked only for the tegra_smmu_ops and then seems you could use
>> dev_iommu_priv_set() in tegra_smmu_of_xlate(), like sun50i-iommu driver
>> does.
> 
> Getting iommu device pointer using driver_find_device_by_fwnode()
> is a common practice in ->probe_device() of other iommu drivers.

Please give me a full list of the IOMMU drivers which use this method.

> But this requires a device_driver pointer that tegra-smmu doesn't
> have. So passing tegra_mc_driver through tegra_smmu_probe() will
> address it.
> 

If you're borrowing code and ideas from other drivers, then at least
please borrow them from a modern good-looking drivers. And I already
pointed out that following cargo cult is not always a good idea.

ARM-SMMU isn't a modern driver and it has legacy code. You shouldn't
copy it blindly. The sun50i-iommu driver was added half year ago, you
may use it as a reference.

Always consult the IOMMU core code. If you're too unsure about
something, then maybe better to start a new thread and ask Joerg about
the best modern practices that IOMMU drivers should use.

WARNING: multiple messages have this Message-ID (diff)
From: Dmitry Osipenko <digetx@gmail.com>
To: Nicolin Chen <nicoleotsuka@gmail.com>
Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	krzk@kernel.org, jonathanh@nvidia.com,
	Thierry Reding <thierry.reding@gmail.com>,
	linux-tegra@vger.kernel.org
Subject: Re: [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and .attach_dev
Date: Fri, 2 Oct 2020 04:55:34 +0300	[thread overview]
Message-ID: <1b621b9d-cdc3-c7aa-2fa2-d728ae2bbc5d@gmail.com> (raw)
In-Reply-To: <20201002010751.GA26971@Asurada-Nvidia>

02.10.2020 04:07, Nicolin Chen пишет:
> On Thu, Oct 01, 2020 at 11:33:38PM +0300, Dmitry Osipenko wrote:
>>>>> If we can't come to an agreement on globalizing mc pointer, would
>>>>> it be possible to pass tegra_mc_driver through tegra_smmu_probe()
>>>>> so we can continue to use driver_find_device_by_fwnode() as v1?
>>>>>
>>>>> v1: https://lkml.org/lkml/2020/9/26/68
>>>>
>>>> tegra_smmu_probe() already takes a struct tegra_mc *. Did you mean
>>>> tegra_smmu_probe_device()? I don't think we can do that because it isn't
>>>
>>> I was saying to have a global parent_driver pointer: similar to
>>> my v1, yet rather than "extern" the tegra_mc_driver, we pass it
>>> through egra_smmu_probe() and store it in a static global value
>>> so as to call tegra_smmu_get_by_fwnode() in ->probe_device().
>>>
>>> Though I agree that creating a global device pointer (mc) might
>>> be controversial, yet having a global parent_driver pointer may
>>> not be against the rule, considering that it is common in iommu
>>> drivers to call driver_find_device_by_fwnode in probe_device().
>>
>> You don't need the global pointer if you have SMMU OF node.
>>
>> You could also get driver pointer from mc->dev->driver.
>>
>> But I don't think you need to do this at all. The probe_device() could
>> be invoked only for the tegra_smmu_ops and then seems you could use
>> dev_iommu_priv_set() in tegra_smmu_of_xlate(), like sun50i-iommu driver
>> does.
> 
> Getting iommu device pointer using driver_find_device_by_fwnode()
> is a common practice in ->probe_device() of other iommu drivers.

Please give me a full list of the IOMMU drivers which use this method.

> But this requires a device_driver pointer that tegra-smmu doesn't
> have. So passing tegra_mc_driver through tegra_smmu_probe() will
> address it.
> 

If you're borrowing code and ideas from other drivers, then at least
please borrow them from a modern good-looking drivers. And I already
pointed out that following cargo cult is not always a good idea.

ARM-SMMU isn't a modern driver and it has legacy code. You shouldn't
copy it blindly. The sun50i-iommu driver was added half year ago, you
may use it as a reference.

Always consult the IOMMU core code. If you're too unsure about
something, then maybe better to start a new thread and ask Joerg about
the best modern practices that IOMMU drivers should use.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2020-10-02  1:55 UTC|newest]

Thread overview: 132+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-30  8:42 [PATCH v3 0/3] iommu/tegra-smmu: Add PCI support Nicolin Chen
2020-09-30  8:42 ` Nicolin Chen
2020-09-30  8:42 ` [PATCH v3 1/3] memory: tegra: Add devm_tegra_get_memory_controller() Nicolin Chen
2020-09-30  8:42   ` Nicolin Chen
2020-09-30  9:07   ` Krzysztof Kozlowski
2020-09-30  9:07     ` Krzysztof Kozlowski
2020-09-30  9:41     ` Nicolin Chen
2020-09-30  9:41       ` Nicolin Chen
2020-09-30 10:27       ` Krzysztof Kozlowski
2020-09-30 10:27         ` Krzysztof Kozlowski
2020-09-30 14:41   ` Dmitry Osipenko
2020-09-30 14:41     ` Dmitry Osipenko
2020-09-30 14:45     ` Krzysztof Kozlowski
2020-09-30 14:45       ` Krzysztof Kozlowski
2020-09-30 15:22       ` Dmitry Osipenko
2020-09-30 15:22         ` Dmitry Osipenko
2020-09-30 15:23   ` Thierry Reding
2020-09-30 15:23     ` Thierry Reding
2020-09-30 15:27     ` Dmitry Osipenko
2020-09-30 15:27       ` Dmitry Osipenko
2020-09-30 15:53     ` Dmitry Osipenko
2020-09-30 15:53       ` Dmitry Osipenko
2020-09-30 16:03       ` Thierry Reding
2020-09-30 16:03         ` Thierry Reding
2020-09-30 16:06         ` Dmitry Osipenko
2020-09-30 16:06           ` Dmitry Osipenko
2020-09-30 16:15           ` Thierry Reding
2020-09-30 16:15             ` Thierry Reding
2020-09-30 16:26             ` Dmitry Osipenko
2020-09-30 16:26               ` Dmitry Osipenko
2020-09-30 16:38               ` Thierry Reding
2020-09-30 16:38                 ` Thierry Reding
2020-09-30 17:32                 ` Dmitry Osipenko
2020-09-30 17:32                   ` Dmitry Osipenko
2020-09-30  8:42 ` [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and .attach_dev Nicolin Chen
2020-09-30  8:42   ` Nicolin Chen
2020-09-30  9:21   ` Krzysztof Kozlowski
2020-09-30  9:21     ` Krzysztof Kozlowski
2020-09-30  9:40     ` Nicolin Chen
2020-09-30  9:40       ` Nicolin Chen
2020-09-30 10:19       ` Krzysztof Kozlowski
2020-09-30 10:19         ` Krzysztof Kozlowski
2020-09-30 14:41   ` Dmitry Osipenko
2020-09-30 14:41     ` Dmitry Osipenko
2020-09-30 15:09   ` Dmitry Osipenko
2020-09-30 15:09     ` Dmitry Osipenko
2020-09-30 20:51     ` Nicolin Chen
2020-09-30 20:51       ` Nicolin Chen
2020-09-30 15:31   ` Thierry Reding
2020-09-30 15:31     ` Thierry Reding
2020-09-30 15:36     ` Dmitry Osipenko
2020-09-30 15:36       ` Dmitry Osipenko
2020-09-30 16:06       ` Thierry Reding
2020-09-30 16:06         ` Thierry Reding
2020-09-30 16:25         ` Dmitry Osipenko
2020-09-30 16:25           ` Dmitry Osipenko
2020-09-30 16:47           ` Thierry Reding
2020-09-30 16:47             ` Thierry Reding
2020-10-01  2:11             ` Dmitry Osipenko
2020-10-01  2:11               ` Dmitry Osipenko
2020-10-01  7:58               ` Thierry Reding
2020-10-01  7:58                 ` Thierry Reding
2020-10-01 19:04                 ` Dmitry Osipenko
2020-10-01 19:04                   ` Dmitry Osipenko
2020-10-05  9:16                   ` Thierry Reding
2020-10-05  9:16                     ` Thierry Reding
2020-10-05  9:38                     ` Dmitry Osipenko
2020-10-05  9:38                       ` Dmitry Osipenko
2020-10-05 10:27                       ` Thierry Reding
2020-10-05 10:27                         ` Thierry Reding
2020-09-30 16:10       ` Thierry Reding
2020-09-30 16:10         ` Thierry Reding
2020-09-30 16:29         ` Dmitry Osipenko
2020-09-30 16:29           ` Dmitry Osipenko
2020-10-01  7:59           ` Thierry Reding
2020-10-01  7:59             ` Thierry Reding
2020-09-30 20:36     ` Nicolin Chen
2020-09-30 20:36       ` Nicolin Chen
2020-09-30 21:24       ` Dmitry Osipenko
2020-09-30 21:24         ` Dmitry Osipenko
2020-09-30 21:32         ` Nicolin Chen
2020-09-30 21:32           ` Nicolin Chen
2020-09-30 21:56           ` Dmitry Osipenko
2020-09-30 21:56             ` Dmitry Osipenko
2020-10-01  1:26             ` Nicolin Chen
2020-10-01  1:26               ` Nicolin Chen
2020-10-01  2:06               ` Dmitry Osipenko
2020-10-01  2:06                 ` Dmitry Osipenko
2020-10-01  2:48                 ` Nicolin Chen
2020-10-01  2:48                   ` Nicolin Chen
2020-10-01  4:04                   ` Dmitry Osipenko
2020-10-01  4:04                     ` Dmitry Osipenko
2020-10-01 10:23                   ` Thierry Reding
2020-10-01 10:23                     ` Thierry Reding
2020-10-01 11:04                     ` Nicolin Chen
2020-10-01 11:04                       ` Nicolin Chen
2020-10-01 20:33                       ` Dmitry Osipenko
2020-10-01 20:33                         ` Dmitry Osipenko
2020-10-02  1:07                         ` Nicolin Chen
2020-10-02  1:07                           ` Nicolin Chen
2020-10-02  1:55                           ` Dmitry Osipenko [this message]
2020-10-02  1:55                             ` Dmitry Osipenko
2020-10-02  2:54                             ` Nicolin Chen
2020-10-02  2:54                               ` Nicolin Chen
2020-10-05  7:24                             ` Thierry Reding
2020-10-05  7:24                               ` Thierry Reding
2020-10-05  7:13                         ` Thierry Reding
2020-10-05  7:13                           ` Thierry Reding
2020-10-05  8:14                           ` Dmitry Osipenko
2020-10-05  8:14                             ` Dmitry Osipenko
2020-10-05  9:31                             ` Thierry Reding
2020-10-05  9:31                               ` Thierry Reding
2020-10-01  9:54                 ` Thierry Reding
2020-10-01  9:54                   ` Thierry Reding
2020-10-01  9:51               ` Thierry Reding
2020-10-01  9:51                 ` Thierry Reding
2020-10-01 10:33                 ` Nicolin Chen
2020-10-01 10:33                   ` Nicolin Chen
2020-10-01 10:42                   ` Thierry Reding
2020-10-01 10:42                     ` Thierry Reding
2020-10-01  9:47       ` Thierry Reding
2020-10-01  9:47         ` Thierry Reding
2020-10-01 10:46       ` Thierry Reding
2020-10-01 10:46         ` Thierry Reding
2020-10-02  1:29         ` Nicolin Chen
2020-10-02  1:29           ` Nicolin Chen
2020-09-30  8:42 ` [PATCH v3 3/3] iommu/tegra-smmu: Add PCI support Nicolin Chen
2020-09-30  8:42   ` Nicolin Chen
2020-09-30 14:53   ` Dmitry Osipenko
2020-09-30 14:53     ` Dmitry Osipenko
2020-09-30 20:03     ` Nicolin Chen
2020-09-30 20:03       ` Nicolin Chen

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