linux-kernel - Re: [PATCH] ata: ahci: Lookup PCS register offset based on PCI device ID

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Message-ID: <679188f7-bb14-1de6-b533-687809fa7bc8@kernel.dk>
Date:   Mon, 12 Aug 2019 08:11:22 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Stephen Douthit <stephend@...icom-usa.com>,
        Christoph Hellwig <hch@...radead.org>
Cc:     "linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH] ata: ahci: Lookup PCS register offset based on PCI device
 ID

On 8/12/19 6:02 AM, Stephen Douthit wrote:
> On 8/10/19 3:43 AM, Christoph Hellwig wrote:
>> On Thu, Aug 08, 2019 at 08:24:31PM +0000, Stephen Douthit wrote:
>>> Intel moved the PCS register from 0x92 to 0x94 on Denverton for some
>>> reason, so now we get to check the device ID before poking it on reset.
>>
>> And now you just match on the new IDs, which means we'll perpetually
>> catch up on any new device.  Dan, can you reach out inside Intel to
>> figure out if there is a way to find out the PCS register location
>> without the PCI ID check?
>>
>>
>>>    static int ahci_pci_reset_controller(struct ata_host *host)
>>>    {
>>>    	struct pci_dev *pdev = to_pci_dev(host->dev);
>>> @@ -634,13 +669,14 @@ static int ahci_pci_reset_controller(struct ata_host *host)
>>>    
>>>    	if (pdev->vendor == PCI_VENDOR_ID_INTEL) {
>>>    		struct ahci_host_priv *hpriv = host->private_data;
>>> +		int pcs = ahci_pcs_offset(host);
>>>    		u16 tmp16;
>>>    
>>>    		/* configure PCS */
>>> -		pci_read_config_word(pdev, 0x92, &tmp16);
>>> +		pci_read_config_word(pdev, pcs, &tmp16);
>>>    		if ((tmp16 & hpriv->port_map) != hpriv->port_map) {
>>> -			tmp16 |= hpriv->port_map;
>>> -			pci_write_config_word(pdev, 0x92, tmp16);
>>> +			tmp16 |= hpriv->port_map & 0xff;
>>> +			pci_write_config_word(pdev, pcs, tmp16);
>>>    		}
>>>    	}
>>
>> And Stephen, while you are at it, can you split this Intel-specific
>> quirk into a separate helper?
> 
> I can do that.  I'll wait until we hear back from Dan if there's a
> better scheme than a device ID lookup.

I'll drop the previous series for now.

-- 
Jens Axboe