Hi:

I was trying to enable auto spin down on my SAMSUNG HD753LJ drive. When I first did a hdparm -i, I got

Model=SAMSUNG HD753LJ                         , FwRev=1AA01112, SerialNo=S13UJDWQ601611
Config={ Fixed }
RawCHS=16383/16/63, TrkSize=34902, SectSize=554, ECCbytes=4
BuffType=DualPortCache, BuffSize=32767kB, MaxMultSect=16, MultSect=?0?
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=1465149168
IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes:  pio0 pio1 pio2 pio3 pio4
DMA modes:  mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
AdvancedPM=yes: disabled (255) WriteCache=enabled
Drive conforms to: unknown:  ATA/ATAPI-3,4,5,6,7

Then I tried hdparm -B 1 -S 252, which went through without an error message:

setting Advanced Power Management level to 0x01 (1)
setting standby to 252 (21 minutes)

But the AdvancedPM readout was still disabled with hdparm -i. Then I tried hdparm -B 10 -S 252, and now I get with hdparm -i

Model=SAMSUNG HD753LJ                         , FwRev=1AA01112, SerialNo=S13UJDWQ601611
Config={ Fixed }
RawCHS=16383/16/63, TrkSize=34902, SectSize=554, ECCbytes=4
BuffType=DualPortCache, BuffSize=32767kB, MaxMultSect=16, MultSect=?0?
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=1465149168
IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes:  pio0 pio1 pio2 pio3 pio4
DMA modes:  mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
AdvancedPM=yes: unknown setting WriteCache=enabled
Drive conforms to: unknown:  ATA/ATAPI-3,4,5,6,7

The unknown setting for AdvancedPM is bothering me. In fact, I can't even disable it now with -B 255, it always says unknown setting. Why is this happening?

This is on the default arch linux 2.6.25 kernel.

Thanks for any help.

Joseph