[PATCH] nouveau, ACPI: fix regression caused by b072e53

[Jiang Liu]

Thanks, Rafael.
Will cc ACPI maillist next time.

On 2014/2/21 4:27, Rafael J. Wysocki wrote:
> On 2/20/2014 10:23 AM, Jiang Liu wrote:
>> Fix regression caused by commit b072e53, which breaks loading nouveau
>> driver on optimus laptops.
>>
>> On some platforms, ACPI _DSM method (nouveau_op_dsm_muid, function 0)
>> has special requirements on the fourth parameter, which is different
>> from ACPI specifications. So revert to the private implementation
>> to check availability of _DSM functions instead of using common
>> acpi_check_dsm() interface.
>>
>> Reported-and-Tested-by: Maarten Lankhorst
>> <maarten.lankhorst at canonical.com>
>> Signed-off-by: Jiang Liu <jiang.liu at linux.intel.com>
> 
> I'm taking this, because the commit that introduced the regression went
> in through my tree.
> 
> In the future I'll appreciate CCing ACPI-related patches to linux-acpi,
> however.
> 
> Thanks,
> Rafael
> 
> 
>> ---
>>   drivers/gpu/drm/nouveau/nouveau_acpi.c |   26
>> ++++++++++++++++++++++++--
>>   1 file changed, 24 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.c
>> b/drivers/gpu/drm/nouveau/nouveau_acpi.c
>> index 4ef83df..83face3 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_acpi.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c
>> @@ -106,6 +106,29 @@ static int nouveau_optimus_dsm(acpi_handle
>> handle, int func, int arg, uint32_t *
>>       return 0;
>>   }
>>   +/*
>> + * On some platforms, _DSM(nouveau_op_dsm_muid, func0) has special
>> + * requirements on the fourth parameter, so a private implementation
>> + * instead of using acpi_check_dsm().
>> + */
>> +static int nouveau_check_optimus_dsm(acpi_handle handle)
>> +{
>> +    int result;
>> +
>> +    /*
>> +     * Function 0 returns a Buffer containing available functions.
>> +     * The args parameter is ignored for function 0, so just put 0 in it
>> +     */
>> +    if (nouveau_optimus_dsm(handle, 0, 0, &result))
>> +        return 0;
>> +
>> +    /*
>> +     * ACPI Spec v4 9.14.1: if bit 0 is zero, no function is supported.
>> +     * If the n-th bit is enabled, function n is supported
>> +     */
>> +    return result & 1 && result & (1 << NOUVEAU_DSM_OPTIMUS_CAPS);
>> +}
>> +
>>   static int nouveau_dsm(acpi_handle handle, int func, int arg)
>>   {
>>       int ret = 0;
>> @@ -207,8 +230,7 @@ static int nouveau_dsm_pci_probe(struct pci_dev
>> *pdev)
>>                  1 << NOUVEAU_DSM_POWER))
>>           retval |= NOUVEAU_DSM_HAS_MUX;
>>   -    if (acpi_check_dsm(dhandle, nouveau_op_dsm_muid, 0x00000100,
>> -               1 << NOUVEAU_DSM_OPTIMUS_CAPS))
>> +    if (nouveau_check_optimus_dsm(dhandle))
>>           retval |= NOUVEAU_DSM_HAS_OPT;
>>         if (retval & NOUVEAU_DSM_HAS_OPT) {
> 
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