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

[Emil Velikov]

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/