[media] gscpa - sn9c20x: Add sd_isoc_init ensuring enough bw when i420 fmt

When using the SN9C20X_I420 fmt the sn9c20x needs more bandwidth
than our regular bandwidth calculations reserve.

This patch adds a sd_isoc_init function, which forces the use of a specific
altsetting when using the SN9C20X_I420 fmt.

This fixes the bottom 10-30% of the image getting corrupted when using
the SN9C20X_I420 fmt (which is the default fmt).

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/drivers/media/video/gspca/sn9c20x.c b/drivers/media/video/gspca/sn9c20x.c
index 7350718c613a..b5fca9166745 100644
--- a/drivers/media/video/gspca/sn9c20x.c
+++ b/drivers/media/video/gspca/sn9c20x.c
@@ -2234,6 +2234,42 @@ static void configure_sensor_output(struct gspca_dev *gspca_dev, int mode)
         }
 }
 
+static int sd_isoc_init(struct gspca_dev *gspca_dev)
+{
+        struct usb_interface *intf;
+        u32 flags = gspca_dev->cam.cam_mode[(int)gspca_dev->curr_mode].priv;
+
+        /*
+         * When using the SN9C20X_I420 fmt the sn9c20x needs more bandwidth
+         * than our regular bandwidth calculations reserve, so we force the
+         * use of a specific altsetting when using the SN9C20X_I420 fmt.
+         */
+        if (!(flags & (MODE_RAW | MODE_JPEG))) {
+                intf = usb_ifnum_to_if(gspca_dev->dev, gspca_dev->iface);
+
+                if (intf->num_altsetting != 9) {
+                        pr_warn("sn9c20x camera with unknown number of alt "
+                                "settings (%d), please report!\n",
+                                intf->num_altsetting);
+                        gspca_dev->alt = intf->num_altsetting;
+                        return 0;
+                }
+
+                switch (gspca_dev->width) {
+                case 160: /* 160x120 */
+                        gspca_dev->alt = 2;
+                        break;
+                case 320: /* 320x240 */
+                        gspca_dev->alt = 6;
+                        break;
+                default:  /* >= 640x480 */
+                        gspca_dev->alt = 9;
+                }
+        }
+
+        return 0;
+}
+
 #define HW_WIN(mode, hstart, vstart) \
 ((const u8 []){hstart, 0, vstart, 0, \
 (mode & MODE_SXGA ? 1280 >> 4 : 640 >> 4), \
@@ -2474,6 +2510,7 @@ static const struct sd_desc sd_desc = {
         .nctrls = ARRAY_SIZE(sd_ctrls),
         .config = sd_config,
         .init = sd_init,
+        .isoc_init = sd_isoc_init,
         .start = sd_start,
         .stopN = sd_stopN,
         .pkt_scan = sd_pkt_scan,