[PATCH] nvme: check for readiness more quickly to speed up boot

[Ahmad Fatoum]

Hi,

On 9/28/26 2:08 PM, Christian Berry wrote:
>   On 9/28/26 10:19, Ahmad Fatoum wrote:
>   > Nitpick: I'd prefer mdelay(1); but you don't need to resend just for this.
> 
>   Thanks for the response,
> 
>   I went with udelay(1000) intentionally, to mirror Linux's
>   usleep_range(1000, 2000) in the equivalent NVMe readiness poll
>   (commit 3e98c2443f5c). mdelay(1) would work too, and I did consider
>   it over udelay(1000) but keeping the barebox and Linux implementations
>   easy to compare side by side seemed worth it. Happy to switch if you
>   feel strongly; otherwise, I'll leave it as-is per your note.

Fair enough. Thanks for the elaboration!

Cheers,
Ahmad

> 
>   Thanks again,
>   Christian
> 
> 
> On Mon, Sep 28, 2026 at 4:18 AM Ahmad Fatoum <a.fatoum at pengutronix.de> wrote:
>>
>> On 9/28/26 1:03 AM, Christian Berry via B4 Relay wrote:
>>> From: Christian Berry <christiankbberry at gmail.com>
>>>
>>> nvme_wait_ready() polls the controller status every 100ms, although
>>> the controller may become ready much sooner. Every probe then waits
>>> at least 100ms longer than needed, and possibly twice, since both
>>> nvme_disable_ctrl() and nvme_enable_ctrl() wait for readiness.
>>>
>>> Poll every millisecond instead, as Linux does since commit
>>> 3e98c2443f5c ("nvme: Check for readiness more quickly, to speed up
>>> boot time"). The overall timeout is still based on elapsed time, so
>>> it is unaffected.
>>>
>>> Tested on an Arm64 SoC with a Samsung 980 SSD in a Gen3 x4
>>> configuration, where PCIe + NVMe probe time dropped from 165 ms to
>>> 65 ms.
>>>
>>> Signed-off-by: Christian Berry <christiankbberry at gmail.com>
>>
>> Reviewed-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
>>
>>> ---
>>>  drivers/nvme/host/core.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>>> index 345707ecfe..9686268d44 100644
>>> --- a/drivers/nvme/host/core.c
>>> +++ b/drivers/nvme/host/core.c
>>> @@ -173,7 +173,7 @@ static int nvme_wait_ready(struct nvme_ctrl *ctrl, u64 cap, bool enabled)
>>>               if ((csts & NVME_CSTS_RDY) == bit)
>>>                       break;
>>>
>>> -             mdelay(100);
>>> +             udelay(1000);
>>
>> Nitpick: I'd prefer mdelay(1); but you don't need to resend just for this.
>>
>> Cheers,
>> Ahmad
>>
>>>
>>>               if (is_timeout(start, timeout)) {
>>>                       dev_err(ctrl->dev,
>>>
>>> ---
>>> base-commit: 983608b439b803f72f12d56d0ab10bd6ba29e536
>>> change-id: 20260927-nvme-ready-poll-4bd640377bab
>>>
>>> Best regards,
>>
>> --
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