Hello, Shane.
Huang, Shane wrote:
>>>> + /* time to wait for DEC is not specified by AHCI spec,
>>>> + * add a retry loop for safety */
>>>> + do {
>>>> + writel(fbs | PORT_FBS_DEC, port_mmio +
>>> PORT_FBS);
>>>> + fbs = readl(port_mmio + PORT_FBS);
>>>> + retries--;
>>>> + } while ((fbs & PORT_FBS_DEC) && retries);
>
>
> At the 2nd thought, if (!pp->fbs_enabled) appears unfortunately
> (although it should not), replacement of if (pp->fbs_enabled) with
> BUG_ON() will lead to the execution of the followed DEC,
Nope, it will result in the executing task being stopped with a scary
stackdump.
> which
> might lead to indeterminate result, because of AHCI v1.2 3.3.16:
>
> Device Error Clear (DEC): ....... Software shall only set this bit to
> '1' if
> PxFBS.EN is set to '1' and PxFBS.SDE is set to '1'.
>
> So I would suggest to keep my original implementation in v2, or put
> BUG_ON to the else case, if you insist, to replace the original
> dev_printk(KERN_ERR).
Problem with the original loop is that it writes PORT_FBS_DEC multiple
times. Assume there are two consecutive device errors, the code might
end up clearing the second one unintentionally.
Thanks.
--
tejun
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