On 2018-01-05 08:20, Devin Heitmueller wrote:
> Hi Brad,
>
> My documents indicate that Register 0x5D and 0x5E are read-only, and
> populated based on the eeprom programming.
>
> On your device, what is the value of those registers prior to you changing them?
>
> If you write to those registers, do they reflect the new values if you
> read them back?
>
> Does changing these values result in any change to the device's
> endpoint configuration (which is typically statically defined when the
> device is probed)?
>
> What precisely is the behavior you were seeing prior to this patch?
>
> Devin
Hey Devin,
We have devices programmed ISOC and bulk in eeprom, but we were seeing
before that bulk transfers were not happening as expected. This included
continuity errors and corrupted packets. After speaking with Empia they
supplied this patch to configure the multiplier explicitly. They also
suggested changing the usb configuration to match this multiplier. This
is done in patch 3/9. I will add some instrumentation to check out the
data you're looking for though. I can say offhand that modifying those
values does have tangible effects. On 'native' machines, there is little
difference, but the multiplier values are make or break in VMWare.
Will reply with the data later.
Cheers,
Brad
> On Thu, Jan 4, 2018 at 7:22 PM, Michael Ira Krufky <mkrufky@xxxxxxxxxxx> wrote:
>> On Thu, Jan 4, 2018 at 7:04 PM, Brad Love <brad@xxxxxxxxxxxxxxxx> wrote:
>>> Set appropriate bulk/ISOC transfer multiplier on capture start.
>>> This sets ISOC transfer to 940 bytes (188 * 5)
>>> This sets bulk transfer to 48128 bytes (188 * 256)
>>>
>>> The above values are maximum allowed according to Empia.
>>>
>>> Signed-off-by: Brad Love <brad@xxxxxxxxxxxxxxxx>
>> :+1
>>
>> Reviewed-by: Michael Ira Krufky <mkrufky@xxxxxxxxxxx>
>>
>>> ---
>>> drivers/media/usb/em28xx/em28xx-core.c | 12 ++++++++++++
>>> 1 file changed, 12 insertions(+)
>>>
>>> diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
>>> index ef38e56..67ed6a3 100644
>>> --- a/drivers/media/usb/em28xx/em28xx-core.c
>>> +++ b/drivers/media/usb/em28xx/em28xx-core.c
>>> @@ -638,6 +638,18 @@ int em28xx_capture_start(struct em28xx *dev, int start)
>>> dev->chip_id == CHIP_ID_EM28174 ||
>>> dev->chip_id == CHIP_ID_EM28178) {
>>> /* The Transport Stream Enable Register moved in em2874 */
>>> + if (dev->dvb_xfer_bulk) {
>>> + /* Max Tx Size = 188 * 256 = 48128 - LCM(188,512) * 2 */
>>> + em28xx_write_reg(dev, (dev->ts == PRIMARY_TS) ?
>>> + EM2874_R5D_TS1_PKT_SIZE :
>>> + EM2874_R5E_TS2_PKT_SIZE,
>>> + 0xFF);
>>> + } else {
>>> + /* TS2 Maximum Transfer Size = 188 * 5 */
>>> + em28xx_write_reg(dev, (dev->ts == PRIMARY_TS) ?
>>> + EM2874_R5D_TS1_PKT_SIZE :
>>> + EM2874_R5E_TS2_PKT_SIZE, 0x05);
>>> + }
>>> if (dev->ts == PRIMARY_TS)
>>> rc = em28xx_write_reg_bits(dev,
>>> EM2874_R5F_TS_ENABLE,
>>> --
>>> 2.7.4
>>>
>
>
