[PATCH][RFC] 8250_dw: unregister dw8250_set_termios for rk3188 chip

[Shuyu Wei]

On Fri, Nov 24, 2017 at 12:34:59AM +0100, Heiko Stuebner wrote:
> Hi,
> 
> Am Donnerstag, 23. November 2017, 23:40:31 CET schrieb Shuyu Wei:
> > On Thu, Nov 23, 2017 at 04:11:12PM +0100, Heiko Stuebner wrote:
> > > 
> > > you actually omitted the output part where sclk_uart2 is actually shown :-) .
> > > 
> > > On my rk3188 radxarock with a kernel build this morning from
> > > the middle of this merge-window, the relevant part of the clock-tree
> > > looks like the following and my serial console works like a charm:
> > > 
> > > xin24m                                   6            6    24000000          0 0
> > > [...]
> > >     pll_gpll                              1            1   594000000          0 0
> > >        gpll                               5            5   594000000          0 0
> > > [...]
> > >          uart_src                        1            1   594000000          0 0
> > >              uart3_pre                    0            0   594000000          0 0
> > >                 uart3_frac                0            0    29700000          0 0
> > >              uart2_pre                    1            1   594000000          0 0
> > >                 uart2_frac                1            1     1843200          0 0
> > >                    sclk_uart2             1            1     1843200          0 0
> > >  [			^^ the important clock]
> > > 
> > > In your dump the sclk_uart2 clock is not muxed to the uart2_frac clock
> > > but to something else but that part is missing from you dump.
> > > 
> > > So clk_round_rate is definitly correct in that it can reach this rate
> > > using the fractional divider and also can sucessfully set this in the
> > > clock framework.
> > > 
> > > Can you show where sclk_uart2 is for you please, as I guess your dump
> > > is with the settermios patch disabled, right?
> > > 
> > > 
> > > Thanks
> > > Heiko
> > 
> > You are right, here is the complete clk_summary from the latest
> > mainline, and my console is now filled with strange characters :-(
> > 
> >    clock                         enable_cnt  prepare_cnt        rate   accuracy   phase
> > ----------------------------------------------------------------------------------------
> >  xin24m                                  11           11    24000000          0 0
> [...]
> >     pll_gpll                              1            1   891000000          0 0
> >        gpll                               3            3   891000000          0 0
> [...]
> >           uart_src                        1            1   891000000          0 0
> >              uart3_pre                    0            0   891000000          0 0
> >                 uart3_frac                0            0    44550000          0 0
> >              uart2_pre                    1            1   891000000          0 0
> >                 uart2_frac                1            1     1843200          0 0
> >                    sclk_uart2             1            1     1843200          0 0
> 
> Just to make sure, I did boot-tests on a lot of different Rockchip socs
> (rk3036, rk3188, rk3288, rk3328, rk3399) with the serial console using
> 8250_dw and working normally on all of them with the most recent
> torvalds kernel (and everything I tested in the past)
> 
> The only difference I see between our two clock dumps is the higher
> gpll clock on your board, but I cannot really imagine that this could be
> and issue.
> 
> So I'm really puzzled by what you see on your board, but don't have
> any specific idea what to test right now.
> 
> 
> Heiko

Good news! I found the cause. It's the barebox bootloader that set the
pll_gpll to the weired 891000000. By manually setting the clock back to
594000000, it worked again! It's time to find the root cause in barebox
:-)