[PATCH] drm/imagination: Defer probe if requested firmware is not available

[Javier Martinez Canillas <javierm@redhat.com>]

The device is initialized in the driver's probe callback and as part of
that initialization, the required firmware is loaded. But this fails if
the driver is built-in and the firmware isn't present in the initramfs:

$ dmesg | grep powervr
[    2.969757] powervr fd00000.gpu: Direct firmware load for powervr/rogue_33.15.11.3_v1.fw failed with error -2
[    2.979727] powervr fd00000.gpu: [drm] *ERROR* failed to load firmware powervr/rogue_33.15.11.3_v1.fw (err=-2)
[    2.989885] powervr: probe of fd00000.gpu failed with error -2

$ ls -lh /lib/firmware/powervr/rogue_33.15.11.3_v1.fw.xz
-rw-r--r-- 1 root root 51K Dec 12 19:00 /lib/firmware/powervr/rogue_33.15.11.3_v1.fw.xz

To prevent the probe to fail for this case, let's defer the probe if the
firmware isn't available. That way, the driver core can retry it and get
the probe to eventually succeed once the root filesystem has been mounted.

If the firmware is also not present in the root filesystem, then the probe
will never succeed and the reason listed in the debugfs devices_deferred:

$ cat /sys/kernel/debug/devices_deferred
fd00000.gpu     powervr: failed to load firmware powervr/rogue_33.15.11.3_v1.fw (err=-517)

Fixes: f99f5f3ea7ef ("drm/imagination: Add GPU ID parsing and firmware loading")
Suggested-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---

 drivers/gpu/drm/imagination/pvr_device.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_device.c b/drivers/gpu/drm/imagination/pvr_device.c
index 1704c0268589..6eda25366431 100644
--- a/drivers/gpu/drm/imagination/pvr_device.c
+++ b/drivers/gpu/drm/imagination/pvr_device.c
@@ -295,8 +295,16 @@ pvr_request_firmware(struct pvr_device *pvr_dev)
 	 */
 	err = request_firmware(&fw, filename, pvr_dev->base.dev);
 	if (err) {
-		drm_err(drm_dev, "failed to load firmware %s (err=%d)\n",
-			filename, err);
+		/*
+		 * Defer probe if the firmware is not available yet (e.g: the driver
+		 * is built-in and the firmware not present in the initramfs image).
+		 */
+		if (err == -ENOENT)
+			err = -EPROBE_DEFER;
+
+		dev_err_probe(drm_dev->dev, err, "failed to load firmware %s (err=%d)\n",
+			      filename, err);
+
 		goto err_free_filename;
 	}
 
-- 
2.43.0