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

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Message-ID: <abfa4b20-2916-d89a-f4d3-b27fca5906b2@silicom-usa.com>
Date:   Mon, 12 Aug 2019 13:02:27 +0000
From:   Stephen Douthit <stephend@...icom-usa.com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     Jens Axboe <axboe@...nel.dk>,
        "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 8/10/19 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.