Re: [PATCH] ata: Disable AHCI ALPM feature for Ampere Computing eMAG SATA

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Hi,

On 27-08-18 20:47, Suman Tripathi wrote:
Due to hardware errata, Ampere Computing eMAG SATA can't support
AHCI ALPM feature. This patch disables the AHCI ALPM feature for
eMAG SATA.

Signed-off-by: Suman Tripathi <stripathi@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Rameshwar Prasad Sahu <rameshwar.sahu@xxxxxxxxxxxxxxxxxxx>

Thank you for the patch. 2 remarks:

1) The ata code is maintained by Jens Axboe (added to the Cc) now, this
is a very recent change, which still has to hit MAINTAINERS

2) See below


---
  drivers/ata/ahci_platform.c | 13 ++++++++++++-
  1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/ata/ahci_platform.c b/drivers/ata/ahci_platform.c
index 99f9a89..0d0233e 100644
--- a/drivers/ata/ahci_platform.c
+++ b/drivers/ata/ahci_platform.c
@@ -26,7 +26,7 @@

  #define DRV_NAME "ahci"

-static const struct ata_port_info ahci_port_info = {
+static struct ata_port_info ahci_port_info = {
  	.flags		= AHCI_FLAG_COMMON,
  	.pio_mask	= ATA_PIO4,
  	.udma_mask	= ATA_UDMA6,

Please do not remove const here, if you need to make a shared info struct
like this non const you are usually doing something wrong (see below).

@@ -41,6 +41,8 @@ static int ahci_probe(struct platform_device *pdev)
  {
  	struct device *dev = &pdev->dev;
  	struct ahci_host_priv *hpriv;
+	struct acpi_device_info *info;
+	acpi_status status;
  	int rc;

  	hpriv = ahci_platform_get_resources(pdev);
@@ -57,6 +59,15 @@ static int ahci_probe(struct platform_device *pdev)
  	if (of_device_is_compatible(dev->of_node, "hisilicon,hisi-ahci"))
  		hpriv->flags |= AHCI_HFLAG_NO_FBS | AHCI_HFLAG_NO_NCQ;

+	status = acpi_get_object_info(ACPI_HANDLE(dev), &info);
+	if (ACPI_SUCCESS(status)) {
+		if (info->valid & ACPI_VALID_HID) {
+			if (!strcmp("APMC0D33", info->hardware_id.string))
+				ahci_port_info.flags |= ATA_FLAG_NO_LPM;
+		}
+		ACPI_FREE(info);
+	}
+
  	rc = ahci_platform_init_host(pdev, hpriv, &ahci_port_info,
  				     &ahci_platform_sht);
  	if (rc)

The normal way to get specific behavior for a specific ACPI HID is
to put the HID in the ahci_acpi_match table and use the acpi_device_id
field to pass some flags (or a pointer).

So the proper way to fix this is to do something like this:

1) Add:

static const struct ata_port_info ahci_port_info_nolpm = {
        .flags          = AHCI_FLAG_COMMON | ATA_FLAG_NO_LPM,
        .pio_mask       = ATA_PIO4,
        .udma_mask      = ATA_UDMA6,
        .port_ops       = &ahci_platform_ops,
};

2) Modify ahci_acpi_match table to:

static const struct acpi_device_id ahci_acpi_match[] = {
	{ "APMC0D33", (unsigned long)&ahci_port_info_nolpm },
        { ACPI_DEVICE_CLASS(PCI_CLASS_STORAGE_SATA_AHCI, 0xffffff) },
        {},
};

3) In ahci_probe() do:

	const struct ata_port_info *port;

	...

	port = acpi_device_get_match_data(dev);
	if (!port)
		port = &ahci_port_info;

	rc = ahci_platform_init_host(pdev, hpriv, port, &ahci_platform_sht);


Regards,

Hans



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