On 3/30/23 20:12, Deepak Ukey wrote: >> On 2/23/23 19:51, Deepak Ukey wrote: >>> Hi All, >>> >>> I have SATA SSD that I am using for robust device functionality testing. >>> I have a setup where SATA SSD is attached to AHCI controller and power >>> to the device is given by power management unit. >>> >>> For the particular test I am doing mutliple power on/off to the device, >>> it is similar to hot unplugged and plug operation. >>> >>> After the 4th iteration of power off and on to device, device link speed >>> is going down to next lower speed, i.e. if device link speed is 6Gbps then >>> it will reduce to 3Gbps. >>> >>> I tried to debug the issue and found that ata_eh_speed_down function is >>> recording the error as ATA_EH_SPDN_SPEED_DOWN and limiting the speed to >>> next lower speed. Afterward SSD starts working on the next lower speed. >>> >>> So can you please tell me why this specific functionality is added. Also >>> is there any way to recover the speed to max speed so that SSD >>> performance should be intact. >> >> Please send a dmesg output of your test to see what is happening. > > Thanks for the response. As you mentioned, we are cutting the power and > device is disappearing/appearing. Please find the below logs for the reference. > > --------------------- > [ 226.463486] ata_eh_link_autopsy: IN > [ 226.463492] ata_eh_link_autopsy: taking speed down action > [ 226.463496] speed_down_verdict_cb: Returning zero > [ 226.463497] speed_down_verdict_cb: Returning zero > [ 226.463497] speed_down_verdict_cb: Returning zero > [ 226.463498] speed_down_verdict_cb: Returning zero > [ 226.463500] speed_down_verdict_cb: Returning zero > [ 226.463501] speed_down_verdict_cb: Returning zero > [ 226.463501] speed_down_verdict_cb: Returning zero > [ 226.463502] speed_down_verdict_cb: Returning zero > [ 226.463504] ata_eh_speed_down_verdict: ATA_EH_SPDN_SPEED_DOWN_1 > [ 226.463504] ata_eh_speed_down: Verdict:2 > [ 226.463506] ata_eh_speed_down: Calling limit Speed 8........ > [ 226.463507] sata_down_spd_limit: speed limit:0 > [ 226.463509] sata_down_spd_limit: Out speed limit:3 > [ 226.463511] ata4: limiting SATA link speed to 3.0 Gbps > [ 226.463512] ata_eh_autopsy:IN > [ 226.463514] ata_eh_reset: IN > [ 230.669238] ata4: SATA link up 3.0 Gbps (SStatus 123 SControl 320) > [ 230.669505] ata4.00: supports DRM functions and may not be fully accessible > [ 230.671982] ata4.00: supports DRM functions and may not be fully accessible > [ 230.674234] ata4.00: configured for UDMA/133 > --------------------------- > > But is there any way that we can recover the speed back to normal if device is > functioning properly after power cut for considerable amount of time. Please try to unplug and re plug the drive, to see if plug-and-play works correctly. Really unplug the drive (not just the power cut). >From the above messages (not standard), it seems that the system did not see the drives going away, and so when power is restored, the state is as before and eh assumes that there was an error and so decides to lower the drive speed. If you want to save power, use the proper ata power management features and put the drive to deep sleep (PM3 mode with SLEEP command) or Standby_z power state (STANDBY IMMEDIATE command). See man hdparm. -- Damien Le Moal Western Digital Research
