[PATCH libdrm] xf86drm: Parse the separate files to retrieve the vendor/device info

[Emil Velikov]

On 8 November 2016 at 15:27, Mauro Santos <registo.mailling at gmail.com> wrote:
> On 08-11-2016 15:00, Emil Velikov wrote:
>> On 8 November 2016 at 13:38, Mauro Santos <registo.mailling at gmail.com> wrote:
>>> On 08-11-2016 11:06, Emil Velikov wrote:
>>>> On 1 November 2016 at 18:47, Mauro Santos <registo.mailling at gmail.com> wrote:
>>>>> On 01-11-2016 18:13, Emil Velikov wrote:
>>>>>> From: Emil Velikov <emil.velikov at collabora.com>
>>>>>>
>>>>>> Parsing config sysfs file wakes up the device. The latter of which may
>>>>>> be slow and isn't required to begin with.
>>>>>>
>>>>>> Reading through config is/was required since the revision is not
>>>>>> available by other means, although with a kernel patch in the way we can
>>>>>> 'cheat' temporarily.
>>>>>>
>>>>>> That should be fine, since no open-source project has ever used the
>>>>>> value.
>>>>>>
>>>>>> Cc: Michel Dänzer <michel.daenzer at amd.com>
>>>>>> Cc: Mauro Santos <registo.mailling at gmail.com>
>>>>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98502
>>>>>> Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
>>>>>> ---
>>>>>> Mauro can you apply this against libdrm and rebuild it. You do _not_
>>>>>> need to rebuild mesa afterwords.
>>>>>>
>>>>>> Thanks
>>>>>> ---
>>>>>>  xf86drm.c | 50 +++++++++++++++++++++++++++++++++++---------------
>>>>>>  1 file changed, 35 insertions(+), 15 deletions(-)
>>>>>>
>>>>>> diff --git a/xf86drm.c b/xf86drm.c
>>>>>> index 52add5e..5a5100c 100644
>>>>>> --- a/xf86drm.c
>>>>>> +++ b/xf86drm.c
>>>>>> @@ -2950,25 +2950,45 @@ static int drmParsePciDeviceInfo(const char *d_name,
>>>>>>                                   drmPciDeviceInfoPtr device)
>>>>>>  {
>>>>>>  #ifdef __linux__
>>>>>> +#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
>>>>>> +    static const char *attrs[] = {
>>>>>> +      "revision", /* XXX: make sure it's always first, see note below */
>>>>>> +      "vendor",
>>>>>> +      "device",
>>>>>> +      "subsystem_vendor",
>>>>>> +      "subsystem_device",
>>>>>> +    };
>>>>>>      char path[PATH_MAX + 1];
>>>>>> -    unsigned char config[64];
>>>>>> -    int fd, ret;
>>>>>> +    unsigned int data[ARRAY_SIZE(attrs)];
>>>>>> +    FILE *fp;
>>>>>> +    int ret;
>>>>>>
>>>>>> -    snprintf(path, PATH_MAX, "/sys/class/drm/%s/device/config", d_name);
>>>>>> -    fd = open(path, O_RDONLY);
>>>>>> -    if (fd < 0)
>>>>>> -        return -errno;
>>>>>> +    for (unsigned i = 0; i < ARRAY_SIZE(attrs); i++) {
>>>>>> +        snprintf(path, PATH_MAX, "/sys/class/drm/%s/device/%s",
>>>>>> +                 d_name, attrs[i]);
>>>>>> +        fp = fopen(path, "r");
>>>>>> +        if (!fp) {
>>>>>> +            /* Note: First we check the revision, since older kernels
>>>>>> +             * may not have it. Default to zero in such cases. */
>>>>>> +            if (i == 0) {
>>>>>> +                data[i] = 0;
>>>>>> +                continue;
>>>>>> +            }
>>>>>> +            return -errno;
>>>>>> +        }
>>>>>>
>>>>>> -    ret = read(fd, config, sizeof(config));
>>>>>> -    close(fd);
>>>>>> -    if (ret < 0)
>>>>>> -        return -errno;
>>>>>> +        ret = fscanf(fp, "%x", &data[i]);
>>>>>> +        fclose(fp);
>>>>>> +        if (ret != 1)
>>>>>> +            return -errno;
>>>>>> +
>>>>>> +    }
>>>>>>
>>>>>> -    device->vendor_id = config[0] | (config[1] << 8);
>>>>>> -    device->device_id = config[2] | (config[3] << 8);
>>>>>> -    device->revision_id = config[8];
>>>>>> -    device->subvendor_id = config[44] | (config[45] << 8);
>>>>>> -    device->subdevice_id = config[46] | (config[47] << 8);
>>>>>> +    device->revision_id = data[0] & 0xff;
>>>>>> +    device->vendor_id = data[1] & 0xffff;
>>>>>> +    device->device_id = data[2] & 0xffff;
>>>>>> +    device->subvendor_id = data[3] & 0xffff;
>>>>>> +    device->subdevice_id = data[4] & 0xffff;
>>>>>>
>>>>>>      return 0;
>>>>>>  #else
>>>>>>
>>>>>
>>>>> I have applied this against libdrm 2.4.71 and I don't see any delays
>>>>> when starting firefox/chromium/thunderbird/glxgears.
>>>>>
>>>>> There is also no indication in dmesg that the dGPU is being
>>>>> reinitialized when starting the programs where I've detected the problem.
>>>>>
>>>> Thanks Mauro. Can you give this a try alongside the kernel fix [1] ?
>>>> I'd love to get the latter merged soon(ish).
>>>> Independent of the kernel side, I might need to go another way for
>>>> libdrm/mesa so I'll CC you on future patches.
>>>>
>>>> Your help is greatly appreciated !
>>>>
>>>> Thanks
>>>> Emil
>>>>
>>>> [1] http://patchwork.ozlabs.org/patch/689975/
>>>>
>>>
>>> I have applied the patch on top of kernel 4.8.6 and I'm using the libdrm
>>> with the patch you sent me previously.
>>>
>>> With this patch things still seem work fine, I don't see any of the
>>> problems I've seen before, but I don't know how to confirm that the
>>> value from sysfs is now being used by libdrm instead of defaulting to zero.
>>>
>> Grr my bad. $libdrm_builddir/tests/drmdevice should do it. You might
>> need to explicitly build it (cd tests && make drmdevice)
>>
>
> When running drmdevice as my user it still wakes up the dGPU. The
> correct device revisions are being reported by I suppose that is not
> being read from sysfs.
>
Based on the output you're spot on - doesn't seem like the revision
sysfs gets used. Most likely drmdevice is linked/using the pre-patch
(system/local?) libdrm.so ?

Note:
tests/drmdevice uses the in-tree libdrm.so while the
tests/.libs/drmdevice should use the system libdrm.so.
To check which one gets picked you can use $LD_DEBUG=libs ./drmdevice

Thanks again !
Emil