serial: clk: bcm2835: Strange effects when using aux-uart in console

[Stefan Wahren]

Hi Martin,

> Martin Sperl <kernel at martin.sperl.org> hat am 13. Februar 2016 um 12:53
> geschrieben:
>
>
> Seems as if you apply it on top of (parts of) my patchset - not on top of a
> clean 4.5-rc3.

sorry about that. I took the wrong directory.

>
> Anyway - after some fixing I get the following outputs -
> the amba-pl011 driver is still patched with debug messages:
>
> After boot with aux-uart as tty:
> root at raspcm:~# dmesg | grep bcm2835
> [ 0.018172] bcm2835: system timer (irq = 27)
> [ 0.711388] bcm2835-aux-uart 20215040.serial: could not get clk: -517
> [ 1.649124] bcm2835-rng 20104000.rng: hwrng registered
> [ 2.051190] bcm2835_clock_on: clk still busy from 6
> [ 2.056159] bcm2835_clock_on: clk now busy from 9

I get the same output here. It belongs to mmc clock.

> [ 8.062743] bcm2835-wdt 20100000.watchdog: Broadcom BCM2835 watchdog timer
> [ 12.042105] bcm2835-i2s 20203000.i2s: can't request region for resource [mem
> 0x20101098-0x20101099]
> [ 12.191701] bcm2835-i2s: probe of 20203000.i2s failed with error -16
>
> Loading the module:
> root at raspcm:~# modprobe amba-pl011
> [ 106.685812] Serial: AMBA PL011 UART driver
> [ 106.693702] uart-pl011 20201000.uart: pl011_setup_port: f0201000 20201000
> [ 106.702109] 20201000.uart: ttyAMA0 at MMIO 0x20201000 (irq = 81, base_baud =
> 0) is a PL011 rev2
> root at raspcm:~#
>
> and starting getty:
> root at raspcm:~# /sbin/getty -a root -L ttyAMA0 115200 vt100
> [ 137.851123] pl011_startup - start
> [ 137.854538] pl011_hwinit - prepare-enable
> [ 137.858772] bcm2835_clock_on: clk still busy from 6
> [ 137.863755] bcm2835_clock_on: clk now busy from 9
> [ 137.868590] pl011_hwinit - prepare-enable - ret = 0
> [ 137.875249] uart-pl011 20201000.uart: no DMA platform data
> [ 137.880940] pl011_startup - exit
> [ 137.888840] pl011_shutdown - start
> [ 137.892360] pl011_shutdown - disable_unprepare
> [ 137.896933] bcm2835_clock_off: clk still busy from 9
> [ 137.902112] pl011_shutdown - exit
> [ 137.907233] pl011_startup - start
> [ 137.910713] pl011_hwinit - prepare-enable
> [ 137.914808] bcm2835_pll_on: PLL still locked from 1
> [ 138.019876] bcm2835-clk 20101000.cprman: plld: couldn't lock PLL
> [ 138.026000] pl011_hwinit - prepare-enable - ret = -110
> [ 138.031266] pl011_startup - error = -110 - disable_unprepare
> [ 138.037048] ------------[ cut here ]------------
> [ 138.041777] WARNING: CPU: 0 PID: 2377 at drivers/clk/clk.c:680
> clk_core_disable+0x34/0xf0()
> [ 138.051063] ---[ end trace dd2f225b2af4c32c ]---
> [ 138.055859] ------------[ cut here ]------------
> [ 138.060627] WARNING: CPU: 0 PID: 2377 at drivers/clk/clk.c:575
> clk_core_unprepare+0x34/0x110()
> [ 138.070321] ---[ end trace dd2f225b2af4c32d ]---
>
> No HDMI output - this time no “flashing” - just no signal.
> Machine is crashed - the attached AXIS USB network card (0b95:772b)
> just transmits identical packets on the network without stopping…
>

According to the datasheet busy bit shouldn't be set while changing the clock.
So this isn't good. I hope this could be fixed, too.

Regards

>