Re: Bug report for ahci-mvebu driver

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 1/25/23 02:02, marius@psihoexpert.ro wrote:
> January 24, 2023 11:54 AM, "Damien Le Moal" <damien.lemoal@opensource.wdc.com> wrote:
> 
>> OK. Good. But from the trace below, it looks like you have the previous
>> patch still applied. Can you try only the above patch ?
> 
> Done:
> [ 15.135173][ T113] hardreset, Online=>Offline
> [ 15.135182][ T113] sata_set_spd_needed, scontrol=0x300
> [ 15.139656][ T113] __sata_set_spd_needed, initial limit=0xFFFFFFFF
> [ 15.144934][ T113] __sata_set_spd_needed, corrected limit=0xFFFFFFFF
> [ 15.151235][ T113] __sata_set_spd_needed, target=0x0
> [ 15.157725][ T113] __sata_set_spd_needed, spd=0x0
> [ 15.162805][ T113] __sata_set_spd_needed, final *scontrol=0x300
> [ 15.168708][ T113] resume, do loop
> [ 15.403902][ T113] resume, after do loop
> [ 15.463901][ T113] debounce, SCR=0x100

[...]

> [ 16.413901][ T113] debounce, SCR=0x0
> [ 16.473901][ T113] debounce, SCR=0x100
> [ 16.477586][ T113] resume, return at end of function
> [ 16.481446][ T113] hardreset, ata_phys_link_offline check failed
> [ 16.486550][ T113] ata2: SATA link down (SStatus 100 SControl 300)
> [ 16.499019][ T113] sata_down_spd_limit: limit 0x1, cur spd 0x0, saved limit 0xffffffff, hw limit
> 0xffffffff
> [ 16.508914][ T113] ata2: limiting SATA link speed to 1.5 Gbps

Marius,

Thanks again for testing.
Could you try a new variation of the fix shown below ? This newer fix
should avoid uselessly going down to 1.5 Gbps as shown above.
Thanks !

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 884ae73b11ea..04938db566e5 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3085,10 +3085,31 @@ int sata_down_spd_limit(struct ata_link *link, u32
spd_limit)
         * If not, use cached value in link->sata_spd.
         */
        rc = sata_scr_read(link, SCR_STATUS, &sstatus);
-       if (rc == 0 && ata_sstatus_online(sstatus))
+       if (rc == 0 && ata_sstatus_online(sstatus)) {
                spd = (sstatus >> 4) & 0xf;
-       else
+       } else {
+               /*
+                * If we reach here, the device is still offline or not
+                * reporting a current speed yet. If we do not have a recorded
+                * speed either, it means that probing the drive is failing,
+                * most likely because problem with link speed autonegotiation
+                * (e.g. reported case with mvebu adapter with a port multiplier
+                * device). In this case, assume that probing was done at Gen3
+                * speed and set the recorded speed to lower Gen2. With this,
+                * the next probe retry will be done after sata_set_spd()
+                * explicitly lowers the link speed. If the device then
+                * responds, the actual maximum speed will be set once
+                * libata-eh finishes the device revalidation.
+                */
+               if (!link->sata_spd) {
+                       link->sata_spd = 2;
+                       ata_link_warn(link,
+                                     "No reported link speed. Assuming %s\n",
+                                     sata_spd_string(link->sata_spd));
+                       return;
+               }
                spd = link->sata_spd;
+       }

        mask = link->sata_spd_limit;
        if (mask <= 1)

-- 
Damien Le Moal
Western Digital Research