linux-kernel - Re: [PATCH] ahci: asm1064: correct count of reported ports

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Message-ID: <Zcuvbzoo7/7c/F1q@x1-carbon>
Date: Tue, 13 Feb 2024 19:05:35 +0100
From: Niklas Cassel <cassel@...nel.org>
To: Andrey Melnikov <temnota.am@...il.com>
Cc: Sergei Shtylyov <sergei.shtylyov@...il.com>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org, dlemoal@...nel.org,
	hdegoede@...hat.com
Subject: Re: [PATCH] ahci: asm1064: correct count of reported ports

On Tue, Feb 13, 2024 at 06:19:10PM +0100, Niklas Cassel wrote:
> On Thu, Feb 08, 2024 at 10:27:11AM +0300, Andrey Melnikov wrote:
> > > On 2/7/24 12:58 PM, Andrey Jr. Melnikov wrote:
> > >
> > > > The ASM1064 SATA host controller always reports wrongly,
> > > > that it has 24 ports. But in reality, it only has four ports.
> > > >
> > > > before:
> > > > ahci 0000:04:00.0: SSS flag set, parallel bus scan disabled
> > > > ahci 0000:04:00.0: AHCI 0001.0301 32 slots 24 ports 6 Gbps 0xffff0f impl SATA mode
> > > > ahci 0000:04:00.0: flags: 64bit ncq sntf stag pm led only pio sxs deso sadm sds apst
> > > >
> > > > after:
> > > > ahci 0000:04:00.0: ASM1064 has only four ports
> > > > ahci 0000:04:00.0: forcing port_map 0xffff0f -> 0xf
> > > > ahci 0000:04:00.0: SSS flag set, parallel bus scan disabled
> > > > ahci 0000:04:00.0: AHCI 0001.0301 32 slots 24 ports 6 Gbps 0xf impl SATA mode
> > > > ahci 0000:04:00.0: flags: 64bit ncq sntf stag pm led only pio sxs deso sadm sds apst
> > > >
> > > >
> > > > Signed-off-by: Andrey Jr. Melnikov <temnota.am@...il.com>
> > > >
> > > > diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> > > > index da2e74fce2d9..ec30d8330d16 100644
> > > > --- a/drivers/ata/ahci.c
> > > > +++ b/drivers/ata/ahci.c
> > > > @@ -671,9 +671,14 @@ MODULE_PARM_DESC(mobile_lpm_policy, "Default LPM policy for mobile chipsets");
> > > >  static void ahci_pci_save_initial_config(struct pci_dev *pdev,
> > > >                                        struct ahci_host_priv *hpriv)
> > > >  {
> > > > -     if (pdev->vendor == PCI_VENDOR_ID_ASMEDIA && pdev->device == 0x1166) {
> > > > -             dev_info(&pdev->dev, "ASM1166 has only six ports\n");
> > > > -             hpriv->saved_port_map = 0x3f;
> > > > +     if (pdev->vendor == PCI_VENDOR_ID_ASMEDIA) {
> > > > +             if (pdev->device == 0x1166) {
> > >
> > >    Maybe *switch* instead?
> > 
> > Ok.
> 
> Hello Andrey,
> 
> do you intend to send out a v2 that uses a switch instead?
> 
> And perhaps take Damien's patch as patch 1/2
> (with Suggested-by: Damien ... of course),
> so that the before/after print in your commit message shows
> the override value.

On second thought, just go ahead and respin your patch using a switch,
as I don't think Damien's patch is fully correct.

He suggested to use hpriv->saved_port_map.

However, that will show the wrong result for platforms using
hpriv->mask_port_map.

As when hpriv->mask_port_map is used, saved_port_map is not set:
https://github.com/torvalds/linux/blob/v6.8-rc4/drivers/ata/libahci.c#L536-L548

However, the local variable "port_map" is updated for both
saved_port_map and mask_port_map cases.

And then at the end:
hpriv->port_map = port_map;
https://github.com/torvalds/linux/blob/v6.8-rc4/drivers/ata/libahci.c#L597

So I think we should print hpriv->port_map,
and not hpriv->saved_port_map.



However.. hpriv->port_map is already printed:
https://github.com/torvalds/linux/blob/v6.8-rc4/drivers/ata/libahci.c#L2617
in the "0x%x impl" print.

So
> before:
> ahci 0000:04:00.0: AHCI 0001.0301 32 slots 24 ports 6 Gbps 0xffff0f impl SATA mode

> after:
> ahci 0000:04:00.0: AHCI 0001.0301 32 slots 24 ports 6 Gbps 0xf impl SATA mode

Actually prints the number of *implemented* ports.


I have to admit that this is a bit confusing.

Personally I would have preferred if we simply printed
"%u ports", hpriv->port_map,

and simply dropped the "0x%x impl" part of the print,
but I'm a bit worried that someone parses this print from user space,
but I guess we must be allowed to improve prints if they are confusing.

Damien, what do you think?


Kind regards,
Niklas