linux-kernel - Re: [PATCH] ata: ahci_platform: add 32-bit quirk for dwc-ahci

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Date:   Thu, 6 Feb 2020 13:54:57 +0200
From:   Roger Quadros <rogerq@...com>
To:     Hans de Goede <hdegoede@...hat.com>, <axboe@...nel.dk>
CC:     <vigneshr@...com>, <nsekhar@...com>, <linux-ide@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH] ata: ahci_platform: add 32-bit quirk for dwc-ahci

Hans,

On 06/02/2020 13:50, Hans de Goede wrote:
> Hi,
> 
> On 2/6/20 12:17 PM, Roger Quadros wrote:
>> On TI Platforms using LPAE, SATA breaks with 64-bit DMA.
>> Restrict it to 32-bit.
>>
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> ---
>>   drivers/ata/ahci_platform.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/ata/ahci_platform.c b/drivers/ata/ahci_platform.c
>> index 3aab2e3d57f3..b925dc54cfa5 100644
>> --- a/drivers/ata/ahci_platform.c
>> +++ b/drivers/ata/ahci_platform.c
>> @@ -62,6 +62,9 @@ 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;
>> +    if (of_device_is_compatible(dev->of_node, "snps,dwc-ahci"))
>> +        hpriv->flags |= AHCI_HFLAG_32BIT_ONLY;
>> +
> 
> The "snps,dwc-ahci" is a generic (non TI specific) compatible which
> is e.g. also used on some exynos devices. So using that to key the
> setting of the 32 bit flag seems wrong to me.

You are right, Vignesh also pointed this out to me offline.

snps,dwc-ahci does indeed support 64-bit addressing, so this patch is wrong.

> 
> IMHO it would be better to introduce a TI specific compatible
> and use that to match on instead (and also adjust the dts files
> accordingly).

The TI platform's TRM does say it has only 36-bits of the controller wired
in the device. If that was the case and DDR address never goes beyond
36-bits, we don't understand why it fails in the first place.

80000000-afcfffff : System RAM
b0000000-feffffff : System RAM
200000000-27fffffff : System RAM

cheers,
-roger

> 
> Regards,
> 
> Hans
> 
> 
> 
>>       port = acpi_device_get_match_data(dev);
>>       if (!port)
>>           port = &ahci_port_info;
>>
> 

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