V4L/DVB (11810): em28xx: properly set packet size based on the device's eeprom configuration.

The em28xx actually has a register that tells the driver what the maximum
packet size is (based on a value programmed into the eeprom).  Make use of
that register instead of assuming a hardcoded value of 564 (since 564 is not
correct for devices that do QAM such as the KWorld 340u).

Note that for now the em2874 code isn't there, falling back to the 564 value,
however this is not a problem since there are not any em2874 based devices in
the current v4l-dvb tree).

Thanks to Jarod Wilson for detecting the initial problem and figuring out that
the isoc configuration was wrong for his device.

Cc: Jarod Wilson <jarod@wilsonet.com>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/drivers/media/video/em28xx/em28xx-core.c b/drivers/media/video/em28xx/em28xx-core.c
index 7375353c04eb..b7a2fedc3904 100644
--- a/drivers/media/video/em28xx/em28xx-core.c
+++ b/drivers/media/video/em28xx/em28xx-core.c
@@ -1012,6 +1012,41 @@ int em28xx_init_isoc(struct em28xx *dev, int max_packets,
 }
 EXPORT_SYMBOL_GPL(em28xx_init_isoc);
 
+/* Determine the packet size for the DVB stream for the given device
+   (underlying value programmed into the eeprom) */
+int em28xx_isoc_dvb_max_packetsize(struct em28xx *dev)
+{
+        unsigned int chip_cfg2;
+        unsigned int packet_size = 564;
+
+        if (dev->chip_id == CHIP_ID_EM2874) {
+                /* FIXME - for now assume 564 like it was before, but the
+                   em2874 code should be added to return the proper value... */
+                packet_size = 564;
+        } else {
+                /* TS max packet size stored in bits 1-0 of R01 */
+                chip_cfg2 = em28xx_read_reg(dev, EM28XX_R01_CHIPCFG2);
+                switch (chip_cfg2 & EM28XX_CHIPCFG2_TS_PACKETSIZE_MASK) {
+                case EM28XX_CHIPCFG2_TS_PACKETSIZE_188:
+                        packet_size = 188;
+                        break;
+                case EM28XX_CHIPCFG2_TS_PACKETSIZE_376:
+                        packet_size = 376;
+                        break;
+                case EM28XX_CHIPCFG2_TS_PACKETSIZE_564:
+                        packet_size = 564;
+                        break;
+                case EM28XX_CHIPCFG2_TS_PACKETSIZE_752:
+                        packet_size = 752;
+                        break;
+                }
+        }
+
+        em28xx_coredbg("dvb max packet size=%d\n", packet_size);
+        return packet_size;
+}
+EXPORT_SYMBOL_GPL(em28xx_isoc_dvb_max_packetsize);
+
 /*
  * em28xx_wake_i2c()
  * configure i2c attached devices