Re: [PATCH] ata: libata-sata: retry hardreset when device detected but PHY not established

[Damien Le Moal <dlemoal@kernel.org>]

On 4/25/26 15:04, Xingui Yang wrote:
> When sata_link_hardreset() detects that the link is offline, it currently
> returns immediately without distinguishing the reason. According to SATA
> specification, the SStatus register's det filed (bits 0-3) indicates:
>   - 0x0: No device detected, PHY not communicating
>   - 0x1: Device detected but PHY communication not established
>   - 0x3: Device detected and PHY communication established
> 
> This patch helps improve device detection reliability and adds a check
> when the link is offline but det filed shows 0x1, return -EAGAIN to
> trigger retry, rather than giving up immediately.
> 
> Signed-off-by: Xingui Yang <yangxingui@huawei.com>

This is a pure ATA patch so please CC the linux-ide list, not the linux-scsi list.

Also, please check your mail setup: your email was in my Junk folder.

> ---
>  drivers/ata/libata-sata.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
> index b9d635088f5f..e5bb92c38e38 100644
> --- a/drivers/ata/libata-sata.c
> +++ b/drivers/ata/libata-sata.c
> @@ -667,8 +667,18 @@ int sata_link_hardreset(struct ata_link *link, const unsigned int *timing,
>  	if (rc)
>  		goto out;
>  	/* if link is offline nothing more to do */
> -	if (ata_phys_link_offline(link))
> +	if (ata_phys_link_offline(link)) {

This is preceeded by a call to sata_link_resume(), which calls
sata_link_debounce() and that function makes sure that DET is stable. So if
after that DET still shows that their is no PHY, there is likely a big problem
with it and it is super slow to be established.

In this case, I do not think that doing another hardreset is the right thing to
do. Have you tried increasing the deadline for hardreset ? That deadline is used
as the limit for the link debounce too.

Do you have a specific controller/device where you see this issue ? What exactly
is the hardware setup where you see this issue ?



> +		u32 sstatus;
> +
> +		if (sata_scr_read(link, SCR_STATUS, &sstatus) == 0 &&
> +		    (sstatus & 0xf) == 0x1) {
> +			ata_link_warn(link, "device detected but PHY not ready (SStatus %X), retrying\n",
> +				      sstatus);
> +			rc = -EAGAIN;
> +		}
> +
>  		goto out;
> +	}
>  
>  	/* Link is online.  From this point, -ENODEV too is an error. */
>  	if (online)


-- 
Damien Le Moal
Western Digital Research