[PATCH] ARM: dts: bcm283x: Fix fifo size for EP 6,7

[Stefan Wahren]

Hi Eric,

> Stefan Wahren <stefan.wahren at i2se.com> hat am 31. Oktober 2017 um 09:43 geschrieben:
> 
> 
> Hi Eric,
> 
> > Eric Anholt <eric at anholt.net> hat am 31. Oktober 2017 um 01:40 geschrieben:
> > 
> > 
> > Stefan Wahren <stefan.wahren at i2se.com> writes:
> > 
> > >> Stefan Wahren <stefan.wahren at i2se.com> hat am 7. Oktober 2017 um 12:16 geschrieben:
> > >> 
> > >> 
> > >> In case the RPi Zero has at least a device connected to the OTG port
> > >> at boot time, the upper limit of tx fifo size for endpoint 6 and 7 is
> > >> also reduced to 512 bytes. So fix this accordingly.
> > >> 
> > >> Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>
> > >> Fixes: 1aa1d858f582 ("ARM: dts: bcm283x: Add dtsi for OTG mode")
> > >
> > > gentle ping ...
> > 
> > I've tried to make sense of this a couple of times, but I don't get it:
> > why does EP 6/7 get reduced to 512 bytes in this case?
> 
> i cannot give you an answer for this specific case.
> 
> Since the dwc2 databook isn't public, i started a thread on linux-usb [1] about proper fifo size configuration. But i didn't get any reply.
> 
> The problem here is there different contraints:
> * the sum of all fifo values must not exceed 3776 bytes
> * each slot have its individual upper limit (available in the BCM2835 datasheet)
> 
> During my tests for OTG mode i missed the specific case above. Now my determined limits of 512 for EP 6 and 7 are contrary to the BCM2835 datasheet. Maybe the Synopsys guys have an answer?
> 
> Btw the values in the downstream tree also violate the contraints. 
> 
> [1] - https://www.spinics.net/lists/linux-usb/msg157200.html

still concerns about this patch, because it's not included in dt-fixes?