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

[Emil Velikov]

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)

> The values in /sys/class/drm/card{0,1}/device/revision match what is
> reported by lspci for the iGPU and dGPU.
> I don't know if it's related but the revision file in
> /sys/class/pci_bus/0000\:03/device/ does show 0xf1 for both GPUs, which
> is different from what is shown in /sys/class/drm/card{0,1}/device/revision.
>
That's perfect, thanks.

0000:03 is (in all likelihood) is the PCI bridge. You can check with
the device uevent/PCI_SLOT_NAME and cross reference with lspci.


Emil