> 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. > > The issue is likely that cutting the drive power is may be not handled the same > way as unpluging the drive and replugging it (try to see if you get the same > result or not). If that is the case, then the drive is simply > disappearing/appearing and that is handled as an error. Too many of these and > libata decides to lower the link speed to try to reduce the number of errors. So > your test is probably not entirely identical to plug/unplug. Losing power is an > error. Unplugging is not. > > > > > Thanks & Regards, > > Deepak Ukey > > > > > > -- > Damien Le Moal > Western Digital Research Thank and regards, Deeepak Ukey
