[U-Boot] [PATCH v1] x86: ahci: Make sure interface is not busy after enabling the port

[Bin Meng]

Hi Simon,

On Wed, Dec 24, 2014 at 3:42 AM, Simon Glass <sjg at chromium.org> wrote:
> Hi Bin,
>
> On 23 December 2014 at 01:01, Bin Meng <bmeng.cn at gmail.com> wrote:
>>
>> Each time U-Boot boots on Intel Crown Bay board, the displayed hard
>> drive information is wrong. It could be either wrong capacity or just
>> a 'Capacity: not available' message. After enabling the debug switch,
>> we can see the scsi inquiry command did not execute successfully.
>> However, doing a 'scsi scan' in the U-Boot shell does not expose
>> this issue.
>
> This sounds like an error condition is not being propagated.

Actually an error condition not checked.

>>
>> SCSI:  Target spinup took 0 ms.
>> SATA link 1 timeout.
>> AHCI 0001.0100 32 slots 2 ports 3 Gbps 0x3 impl SATA mode
>> flags: ncq stag pm led clo only pmp pio slum part ccc apst
>> scanning bus for devices...
>> ahci_device_data_io: 0 byte transferred.   <--- scsi inquiry fails
>> ahci_device_data_io: 512 byte transferred.
>> ahci_device_data_io: 512 byte transferred.
>> ahci_device_data_io: 512 byte transferred.
>>   Device 0: (0:0) Vendor: ATA Prod.:  Rev: ?8
>>               Type: Hard Disk
>>                           Capacity: 912968.3 MB = 891.5 GB (1869759264 x 512)
>>                           Found 1 device(s).
>>
>> So uninitialized contents on the stack were passed to dev_print() to
>> display those wrong information.
>>
>> The symptom were observed on two hard drives (one is Seagate, the
>> other one is Western Digital). The fix is to make sure the AHCI
>> interface is not busy by checking the error and status information
>> from task file register after enabling the port in ahci_port_start()
>> before proceeding other operations like scsi_scan().
>>
>> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
>>
>> ---
>>
>>  drivers/block/ahci.c | 15 ++++++++++++++-
>>  1 file changed, 14 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/block/ahci.c b/drivers/block/ahci.c
>> index c9a3beb..7ca8f40 100644
>> --- a/drivers/block/ahci.c
>> +++ b/drivers/block/ahci.c
>> @@ -505,8 +505,9 @@ static int ahci_port_start(u8 port)
>>  {
>>         struct ahci_ioports *pp = &(probe_ent->port[port]);
>>         volatile u8 *port_mmio = (volatile u8 *)pp->port_mmio;
>> -       u32 port_status;
>> +       u32 port_status, tf_data;
>>         u32 mem;
>> +       int i = 0;
>>
>>         debug("Enter start port: %d\n", port);
>>         port_status = readl(port_mmio + PORT_SCR_STAT);
>> @@ -564,6 +565,18 @@ static int ahci_port_start(u8 port)
>>                           PORT_CMD_POWER_ON | PORT_CMD_SPIN_UP |
>>                           PORT_CMD_START, port_mmio + PORT_CMD);
>>
>> +       /*
>> +        * Make sure interface is not busy based on error and status
>> +        * information from task file data register before proceeding
>> +        */
>> +       while (i < WAIT_MS_SPINUP) {
>> +               tf_data = readl(port_mmio + PORT_TFDATA);
>> +               if (!(tf_data & ATA_BUSY))
>> +                       break;
>> +               udelay(1000);
>> +               i++;
>> +       }
>> +
>
> Doesn't this fall through after a timeout and fail to report an error?

Ah, yes! We should return error code when timeout. But some other
routines in the scsi initialization path do no check return values,
like initr_scsi()->scsi_init()->scsi_low_level_init().

> As a matter of style I think something like the below is better
> because it the timeout will be more accurate in the case where you
> have a lot of processing each time around the loop.
>
> static int wait_spinup(void)
> {
> ulong start;
>
> start = get_timer(0);
> do {
>   tf_data = ...;
>   if (!((tf_data & ATA_BUSY))
>     return 0;
> while (get_timer(start) < WAIT_MS_SPINUP);
> return -ETIMEDOUT;
> }

Looks like the original codes there are using i++ style for the
timeout check instead of get_timer().

> Also how does this relate to the existing spinup delay code in ahci_host_init()?

This seems to me they are not related. Per my understanding, the check
we need here is because we write something to the port command
register, but we missed the task file data busy indication.

writel_with_flush(PORT_CMD_ICC_ACTIVE | PORT_CMD_FIS_RX |
 PORT_CMD_POWER_ON | PORT_CMD_SPIN_UP |
 PORT_CMD_START, port_mmio + PORT_CMD);

[snip]

Regards,
Bin