Re: [PATCH v2] x86/platform/intel-mid: Retrofit pci_platform_pm_ops ->get_state hook

[Bjorn Helgaas <helgaas@kernel.org>]

On Sun, Oct 09, 2016 at 02:46:29PM +0200, Lukas Wunner wrote:
> Commit cc7cc02bada8 ("PCI: Query platform firmware for device power
> state") augmented struct pci_platform_pm_ops with a ->get_state hook and
> implemented it for acpi_pci_platform_pm, the only pci_platform_pm_ops
> existing till v4.7.
> 
> However v4.8 introduced another pci_platform_pm_ops for Intel Mobile
> Internet Devices with commit 5823d0893ec2 ("x86/platform/intel-mid: Add
> Power Management Unit driver").  It is missing the ->get_state hook,
> which is fatal since pci_set_platform_pm() enforces its presence.

I assume Andy tested 5823d0893ec2, so apparently "fatal" here doesn't
mean a panic on the MIDs?  I'm wondering (1) exactly what the user-
visible failure mode is, and (2) whether there's anything we can do to
avoid omissions like this in the future.

pci_set_platform_pm() does indeed return -EINVAL if it receives a
pci_platform_pm_ops with a NULL ops->get_state pointer, but
unfortunately neither of the callers checks that return code.

> Retrofit mid_pci_platform_pm with the missing callback to fix the
> breakage.
> 
> Cc: x86@kernel.org
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> Acked-and-tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Fixes: 5823d0893ec2 ("x86/platform/intel-mid: Add Power Management Unit driver")
Acked-by: Bjorn Helgaas <bhelgaas@google.com>

Sounds like this should be marked for stable, since v4.8 contains
5823d0893ec2 and is apparently broken?

I agree this should go via the x86 tree, since that's how 5823d0893ec2
was merged.

> ---
> Changes v1 -> v2:
> - Cast return value of intel_mid_pci_get_power_state() to
>   (__force pci_power_t) to avoid "sparse -D__CHECK_ENDIAN__" warning.
> 
>  arch/x86/include/asm/intel-mid.h  |  1 +
>  arch/x86/platform/intel-mid/pwr.c | 19 +++++++++++++++++++
>  drivers/pci/pci-mid.c             |  6 ++++++
>  3 files changed, 26 insertions(+)
> 
> diff --git a/arch/x86/include/asm/intel-mid.h b/arch/x86/include/asm/intel-mid.h
> index 9d6b097..4511c10 100644
> --- a/arch/x86/include/asm/intel-mid.h
> +++ b/arch/x86/include/asm/intel-mid.h
> @@ -17,6 +17,7 @@
>  
>  extern int intel_mid_pci_init(void);
>  extern int intel_mid_pci_set_power_state(struct pci_dev *pdev, pci_power_t state);
> +extern pci_power_t intel_mid_pci_get_power_state(struct pci_dev *pdev);
>  
>  #define INTEL_MID_PWR_LSS_OFFSET	4
>  #define INTEL_MID_PWR_LSS_TYPE		(1 << 7)
> diff --git a/arch/x86/platform/intel-mid/pwr.c b/arch/x86/platform/intel-mid/pwr.c
> index c901a34..cae8d9b 100644
> --- a/arch/x86/platform/intel-mid/pwr.c
> +++ b/arch/x86/platform/intel-mid/pwr.c
> @@ -260,6 +260,25 @@ int intel_mid_pci_set_power_state(struct pci_dev *pdev, pci_power_t state)
>  }
>  EXPORT_SYMBOL_GPL(intel_mid_pci_set_power_state);
>  
> +pci_power_t intel_mid_pci_get_power_state(struct pci_dev *pdev)
> +{
> +	struct mid_pwr *pwr = midpwr;
> +	int id, reg, bit;
> +	u32 power;
> +
> +	if (!pwr || !pwr->available)
> +		return PCI_UNKNOWN;
> +
> +	id = intel_mid_pwr_get_lss_id(pdev);
> +	if (id < 0)
> +		return PCI_UNKNOWN;
> +
> +	reg = (id * LSS_PWS_BITS) / 32;
> +	bit = (id * LSS_PWS_BITS) % 32;
> +	power = mid_pwr_get_state(pwr, reg);
> +	return (__force pci_power_t)((power >> bit) & 3);
> +}
> +
>  int intel_mid_pwr_get_lss_id(struct pci_dev *pdev)
>  {
>  	int vndr;
> diff --git a/drivers/pci/pci-mid.c b/drivers/pci/pci-mid.c
> index c878aa7..a8b52dc 100644
> --- a/drivers/pci/pci-mid.c
> +++ b/drivers/pci/pci-mid.c
> @@ -29,6 +29,11 @@ static int mid_pci_set_power_state(struct pci_dev *pdev, pci_power_t state)
>  	return intel_mid_pci_set_power_state(pdev, state);
>  }
>  
> +static pci_power_t mid_pci_get_power_state(struct pci_dev *pdev)
> +{
> +	return intel_mid_pci_get_power_state(pdev);
> +}
> +
>  static pci_power_t mid_pci_choose_state(struct pci_dev *pdev)
>  {
>  	return PCI_D3hot;
> @@ -52,6 +57,7 @@ static bool mid_pci_need_resume(struct pci_dev *dev)
>  static struct pci_platform_pm_ops mid_pci_platform_pm = {
>  	.is_manageable	= mid_pci_power_manageable,
>  	.set_state	= mid_pci_set_power_state,
> +	.get_state	= mid_pci_get_power_state,
>  	.choose_state	= mid_pci_choose_state,
>  	.sleep_wake	= mid_pci_sleep_wake,
>  	.run_wake	= mid_pci_run_wake,
> -- 
> 2.9.3
> 
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