linux-kernel - Re: [PATCH v6 05/45] drm/amd: Add a new helper for loading/validating microcode

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Date:   Wed, 4 Jan 2023 23:37:35 -0600
From:   Mario Limonciello <mario.limonciello@....com>
To:     "Lazar, Lijo" <lijo.lazar@....com>,
        Alex Deucher <alexander.deucher@....com>,
        linux-kernel@...r.kernel.org
Cc:     Javier Martinez Canillas <javierm@...hat.com>,
        Carlos Soriano Sanchez <csoriano@...hat.com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, christian.koenig@....com,
        "Pan, Xinhui" <Xinhui.Pan@....com>
Subject: Re: [PATCH v6 05/45] drm/amd: Add a new helper for loading/validating
 microcode

On 1/4/23 23:29, Lazar, Lijo wrote:
> 
> 
> On 1/5/2023 10:53 AM, Mario Limonciello wrote:
>> On 1/4/23 23:07, Lazar, Lijo wrote:
>>>
>>>
>>> On 1/5/2023 9:12 AM, Mario Limonciello wrote:
>>>> All microcode runs a basic validation after it's been loaded. Each
>>>> IP block as part of init will run both.
>>>>
>>>> Introduce a wrapper for request_firmware and amdgpu_ucode_validate.
>>>> This wrapper will also remap any error codes from request_firmware
>>>> to -ENODEV.  This is so that early_init will fail if firmware couldn't
>>>> be loaded instead of the IP block being disabled.
>>>>
>>>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
>>>> ---
>>>> v5->v6:
>>>>   * Fix argument to be ** not *
>>>> ---
>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.c | 36 
>>>> +++++++++++++++++++++++
>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.h |  3 ++
>>>>   2 files changed, 39 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.c 
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.c
>>>> index eafcddce58d3..8ebfec12da87 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.c
>>>> @@ -1312,3 +1312,39 @@ void amdgpu_ucode_ip_version_decode(struct 
>>>> amdgpu_device *adev, int block_type,
>>>>       snprintf(ucode_prefix, len, "%s_%d_%d_%d", ip_name, maj, min, 
>>>> rev);
>>>>   }
>>>> +
>>>> +/*
>>>> + * amdgpu_ucode_request - Fetch and validate amdgpu microcode
>>>> + *
>>>> + * @adev: amdgpu device
>>>> + * @fw: pointer to load firmware to
>>>> + * @fw_name: firmware to load
>>>> + *
>>>> + * This is a helper that will use request_firmware and 
>>>> amdgpu_ucode_validate
>>>> + * to load and run basic validation on firmware. If the load fails, 
>>>> remap
>>>> + * the error code to -ENODEV, so that early_init functions will 
>>>> fail to load.
>>>> + */
>>>> +int amdgpu_ucode_request(struct amdgpu_device *adev, const struct 
>>>> firmware **fw,
>>>> +             const char *fw_name)
>>>> +{
>>>> +    int err = request_firmware(fw, fw_name, adev->dev);
>>>> +
>>>> +    if (err)
>>>> +        return -ENODEV;
>>>> +    err = amdgpu_ucode_validate(*fw);
>>>> +    if (err)
>>>> +        dev_dbg(adev->dev, "\"%s\" failed to validate\n", fw_name);
>>>> +
>>>
>>> Missed this earlier. If validate fails, shouldn't this undo the 
>>> request operation by calling release?
>>
>> Actually that was original design, but there is one place in the 
>> codebase that expects that ucode validation can fail, and so leave the 
>> evaluate of error code and cleanup outside of helper.
>>
> 
> I see. Does request_firmware assure that fw pointer be always NULL if it 
> fails? Or should that be done here if request_ fails? In subsequent 
> patches, I see clients calling release without checking what caused the 
> failure.

Yes, according to docs 
(https://docs.kernel.org/next/driver-api/firmware/request_firmware.html#request-firmware-api-expected-driver-use)

> 
> Thanks,
> Lijo
> 
>>>
>>> Thanks,
>>> Lijo
>>>
>>>> +    return err;
>>>> +}
>>>> +
>>>> +/*
>>>> + * amdgpu_ucode_release - Release firmware microcode
>>>> + *
>>>> + * @fw: pointer to firmware to release
>>>> + */
>>>> +void amdgpu_ucode_release(const struct firmware **fw)
>>>> +{
>>>> +    release_firmware(*fw);
>>>> +    *fw = NULL;
>>>> +}
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.h 
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.h
>>>> index 552e06929229..848579d4988b 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.h
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.h
>>>> @@ -544,6 +544,9 @@ void amdgpu_ucode_print_sdma_hdr(const struct 
>>>> common_firmware_header *hdr);
>>>>   void amdgpu_ucode_print_psp_hdr(const struct 
>>>> common_firmware_header *hdr);
>>>>   void amdgpu_ucode_print_gpu_info_hdr(const struct 
>>>> common_firmware_header *hdr);
>>>>   int amdgpu_ucode_validate(const struct firmware *fw);
>>>> +int amdgpu_ucode_request(struct amdgpu_device *adev, const struct 
>>>> firmware **fw,
>>>> +             const char *fw_name);
>>>> +void amdgpu_ucode_release(const struct firmware **fw);
>>>>   bool amdgpu_ucode_hdr_version(union amdgpu_firmware_header *hdr,
>>>>                   uint16_t hdr_major, uint16_t hdr_minor);
>>