Re: [PATCH 1/2] ata: ahci: Add force LPM policy quirk for ASUS B1400CEAE

Jian-Hong Pan
2024-02-02T08:49:36Z

Niklas Cassel <cassel@kernel.org> 於 2024年2月1日 週四 下午11:01寫道：
>
> On Wed, Jan 31, 2024 at 11:43:59PM +0100, Niklas Cassel wrote:
> > On Wed, Jan 31, 2024 at 07:08:12AM -0400, Daniel Drake wrote:
>
> (snip)
>
> > In libata we perform a reset of the port at boot, see:
> > libata-sata.c:sata_link_hardreset()
> > after writing to SControl, we call
> > libata-core.c:ata_wait_ready() that will poll for the port being ready
> > by calling the check_ready callback.
> > For AHCI, this callback funcion is set to:
> > libahci.c:ahci_check_ready().
> >
> > A reset should take the device out of deep power state and should be
> > sufficient to establish a connection (and that also seems to be the
> > case when not using Intel VMD).
> >
> > However, if you want to debug, I would start by adding prints to
> > libata-sata.c:sata_link_hardreset()
> > libata-core.c:ata_wait_ready()
> > libahci.c:ahci_check_ready().
>
> FWIW, this will dump SStatus.DET every time the check_ready callback function
> (ahci_check_ready()) is called:
>
>
> diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
> index 1a63200ea437..0467e150601e 100644
> --- a/drivers/ata/libahci.c
> +++ b/drivers/ata/libahci.c
> @@ -1533,6 +1533,12 @@ int ahci_check_ready(struct ata_link *link)
> {
> void __iomem *port_mmio = ahci_port_base(link->ap);
> u8 status = readl(port_mmio + PORT_TFDATA) & 0xFF;
> + u32 cur = 0;
> +
> + sata_scr_read(link, SCR_STATUS, &cur);
> +
> + ata_link_info(link, "BUSY ? %d (status: %#x) SStatus.DET: %#x\n",
> + status & ATA_BUSY, status, cur & 0xf);
>
> return ata_check_ready(status);
> }

I think I can join the test based on kernel v6.8-rc2, too.

The original ASUS B1400CEAE has only one NVMe SSD. I prepare the
patch ("ata: ahci: Add force LPM policy quirk for ASUS B1400CEAE") to
fix the power consumption issue for s2idle with enabled VMD.

The patch is a quirk limiting ASUS B1400CEAE only, not generic for the
SATA controller [8086:a0d3]. Then, I install another SATA HDD into
ASUS B1400CEAE for test. The SATA HDD shows up and works.

$ dmesg | grep SATA
[ 0.785120] ahci 10000:e0:17.0: AHCI 0001.0301 32 slots 1 ports 6
Gbps 0x1 impl SATA mode
[ 0.785269] ata1: SATA max UDMA/133 abar m2048@0x76102000 port
0x76102100 irq 144 lpm-pol 3
[ 1.096684] ata1: SATA link up 6.0 Gbps (SStatus 133 SControl 300)

However, if I simply revert the commit 6210038aeaf4 ("ata: ahci:
Revert "ata: ahci: Add Tiger Lake UP{3,4} AHCI controller"") (fix the
conflict, of course), then the SATA HDD disappears!!? Both
CONFIG_SATA_MOBILE_LPM_POLICY=3 and 0 can reproduce the issue.

$ dmesg | grep SATA
[ 0.783211] ahci 10000:e0:17.0: AHCI 0001.0301 32 slots 1 ports 6
Gbps 0x1 impl SATA mode
[ 0.783399] ata1: SATA max UDMA/133 abar m2048@0x76102000 port
0x76102100 irq 144 lpm-pol 3
[ 1.096685] ata1: SATA link down (SStatus 4 SControl 300)

Here is the dmesg of reverting ("ata: ahci: Revert "ata: ahci: Add
Tiger Lake UP{3,4} AHCI controller"")
https://bugzilla.kernel.org/show_bug.cgi?id=217114#c27
The code already includes the debug message in ahci_check_ready() from
Niklas. However, the dmesg does not show the "BUSY ? ..." from
ahci_check_ready().

From these scenarios mentioned above, they all apply LPM policy to the
SATA controller [8086:a0d3]. But, they apply LPM policy at different
time:
* The patch ("ata: ahci: Add force LPM policy quirk for ASUS
B1400CEAE") applies LPM policy in early ahci_init_one(), which is the
probe callback.
* Reverting 6210038aeaf4 ("ata: ahci: Revert "ata: ahci: Add Tiger
Lake UP{3,4} AHCI controller"") applies LPM policy via "ahci_pci_tbl"
table.

Jian-Hong Pan