ahci timeout

As my old PATA hard disk was failing, I had to replace it with a new SATA 
drive where I moved my FreeBSDs installations, as PATA drives are not easy to 
find these days.
So I had to move one of my data drive from a VIA8237A SATA controller to the 
last free SATA slot on a Marvell 88SX6121 to make room for the new hd.
The hd I moved was working perfectly when connected to the VIA controller.
Now, with the Marvell I'm getting messages like the following twos while using 
the disk:
    ahcich0: Timeout on slot 10
    ahcich0: is 00000000 cs 3ffff800 ss 3ffffc00 rs 3ffffc00 tfd 50010040 serr 
00000000
    
    ahcich0: Timeout on slot 5
    ahcich0: is 00000000 cs 00000180 ss 000001e0 rs 000001e0 tfd 50040040 serr 
00000000

This doesn't happen regularly. For example downloading from a slow website on 
it, so few kb/s, is ok.
But if I copy files from the disk attacked to the Marvell controller to 
another another disk, or for example run md5 on some files, it's very likely to 
happen.
The process accessing the disk can not be killed even with -9, ^C does 
nothing, and umount doesn't exit.
If I'm copying files on it from another disk it can't be unmounted too as the 
unkillable process has it in use.
On shutdown many disk doesn't get unmounted, so there are a lot of fsck on 
boot, and on CURRENT (last built yesterday), FreeBSD enter debugger as it fail 
flushing disk caches.

Relevant part from dmesg:

atapci0: <Marvell 88SX6121 UDMA133 controller> port 0xdc00-0xdc07,0xd880-
0xd883,0xd800-0xd807,0xd480-0xd483,0xd400-0xd40f mem 0xfbdffc00-0xfbdfffff irq 
28 at device 0.0 on pci6
ahci0: <Marvell 88SX6121 AHCI SATA controller> on atapci0
ahci0: AHCI v1.00 with 2 3Gbps ports, Port Multiplier supported
ahcich0: <AHCI channel> at channel 0 on ahci0
ahcich1: <AHCI channel> at channel 1 on ahci0
ata2: <ATA channel 0> on atapci0
atapci1: <VIA 8237A SATA150 controller> port 0xbc00-0xbc07,0xb880-0xb883,
0xb800-0xb807,0xb480-0xb483,0xb400-0xb40f,0xb000-0xb0ff irq 21 at device 15.0 
on pci0
ata3: <ATA channel 0> on atapci1
ata4: <ATA channel 1> on atapci1
atapci2: <VIA 8237A UDMA133 controller> port 0x1f0-0x1f7,0x3f6,0x170-0x177,
0x376,0xfc00-0xfc0f at device 15.1 on pci0
ata0: <ATA channel 0> on atapci2
ata1: <ATA channel 1> on atapci2

ada0 at ahcich0 bus 0 scbus0 target 0 lun 0
ada0: <ST31000528AS CC44> ATA-8 SATA 2.x device
ada0: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes)
ada0: Command Queueing enabled
ada0: 953869MB (1953525168 512 byte sectors: 16H 63S/T 16383C)
ada1 at ata3 bus 0 scbus3 target 0 lun 0
ada1: <WDC WD2500KS-00MJB0 02.01C03> ATA-7 SATA 2.x device
ada1: 150.000MB/s transfers (SATA 1.x, UDMA5, PIO 8192bytes)
ada1: 238475MB (488397168 512 byte sectors: 16H 63S/T 16383C)
ada2 at ata4 bus 0 scbus4 target 0 lun 0
ada2: <ST3500320AS SD1A> ATA-8 SATA 1.x device
ada2: 150.000MB/s transfers (SATA 1.x, UDMA5, PIO 8192bytes)
ada2: 476940MB (976773168 512 byte sectors: 16H 63S/T 16383C)
ada3 at ata0 bus 0 scbus5 target 0 lun 0
ada3: <MAXTOR STM3160212A 3.AAJ> ATA-7 device
ada3: 100.000MB/s transfers (UDMA5, PIO 8192bytes)
ada3: 152627MB (312581808 512 byte sectors: 16H 63S/T 16383C)