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SubjectRE: [PATCH] ata: Disable AHCI ALPM feature for Ampere Computing eMAG SATA
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Hi Hans

Thanks for your fast response.

With regards,
Suman

Please note my new email address → stripathi@amperecomputing.com

-----Original Message-----
From: Hans de Goede <hdegoede@redhat.com>
Sent: Monday, August 27, 2018 12:09 PM
To: Suman Tripathi <stripathi@amperecomputing.com>; tj@kernel.org; linux-ide@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; joe@perches.com; arnd@arndb.de; gregkh@linuxfoundation.org
Cc: Open Source Submission <patches@amperecomputing.com>; Rameshwar P Sahu <Rameshwar.Sahu@amperecomputing.com>; Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH] ata: Disable AHCI ALPM feature for Ampere Computing eMAG SATA

[NOTICE: This email originated from an external sender. Please be mindful of safe email handling and proprietary information protection practices.] ________________________________________________________________________________________________________________________

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@amperecomputing.com>
> Signed-off-by: Rameshwar Prasad Sahu
> <rameshwar.sahu@amperecomputing.com>

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
[Suman Tripathi] Didn't still see him for libata subsystem. Surely will fix the comments cc him for the next version. I see him in the scsi subsystem.

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).
[Suman Tripathi] Agree on this.

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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