Subject: Re: [PATCH 15/27] powerpc/eeh: I/O chip EEH state retrieval

From: Benjamin Herrenschmidt <[email-masked]>
Date: Tue, 11 Jun 2013 17:37:04 +1000

On Wed, 2013-06-05 at 15:34 +0800, Gavin Shan wrote:
> The patch adds I/O chip backend to retrieve the state for the
> indicated PE. While the PE state is temperarily unavailable,
> we return the default wait time (1000ms).
> 
> Signed-off-by: Gavin Shan <[email-masked]>
> ---
>  arch/powerpc/platforms/powernv/eeh-ioda.c |  102 ++++++++++++++++++++++++++++-
>  1 files changed, 101 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/eeh-ioda.c b/arch/powerpc/platforms/powernv/eeh-ioda.c
> index e24622e..3c72321 100644
> --- a/arch/powerpc/platforms/powernv/eeh-ioda.c
> +++ b/arch/powerpc/platforms/powernv/eeh-ioda.c
> @@ -125,10 +125,110 @@ static int ioda_eeh_set_option(struct eeh_pe *pe, int option)
>  	return ret;
>  }
>  
> +/**
> + * ioda_eeh_get_state - Retrieve the state of PE
> + * @pe: EEH PE
> + * @state: return value
> + *
> + * The PE's state should be retrieved from the PEEV, PEST
> + * IODA tables. Since the OPAL has exported the function
> + * to do it, it'd better to use that.
> + */
> +static int ioda_eeh_get_state(struct eeh_pe *pe, int *state)
> +{

So everywhere you have this "state" argument which isn't a state but a delay ...

Moreover you only initialize it in one specific case and leave it otherwise
uninitialized....

At the very least, init it to 0 by default as to not leave a dangling
"return argument" like that. However, I still have a problem with it:

> +	case OPAL_EEH_STOPPED_TEMP_UNAVAIL:
> +		result |= EEH_STATE_UNAVAILABLE;
> +		if (state)
> +			*state = 1000;
> +		break;

This is the *only* case where we return anything here. Why do we bother
then and not have the upper layer simply wait one second whenever it gets
a temp unavailable result (btw, you didn't differenciate temp unavailable
from permanently unavailable in your API).

This has impacts on patch 18/27 which I'll cover here:

> +/**
> + * powernv_eeh_set_option - Initialize EEH or MMIO/DMA reenable
> + * @pe: EEH PE
> + * @option: operation to be issued
> + *
> + * The function is used to control the EEH functionality globally.
> + * Currently, following options are support according to PAPR:
> + * Enable EEH, Disable EEH, Enable MMIO and Enable DMA
> + */
> +static int powernv_eeh_set_option(struct eeh_pe *pe, int option)
> +{
> +	struct pci_controller *hose = pe->phb;
> +	struct pnv_phb *phb = hose->private_data;
> +	int ret = -EEXIST;
> +
> +	/*
> +	 * What we need do is pass it down for hardware
> +	 * implementation to handle it.
> +	 */
> +	if (phb->eeh_ops && phb->eeh_ops->set_option)
> +		ret = phb->eeh_ops->set_option(pe, option);
> +
> +	return ret;
> +}

Should we implement something here ? IE. Should we look into
disabling freezing in the PHB via the firmware ? Or we just don't care ?

> +/**
> + * powernv_eeh_get_pe_addr - Retrieve PE address
> + * @pe: EEH PE
> + *
> + * Retrieve the PE address according to the given tranditional
> + * PCI BDF (Bus/Device/Function) address.
> + */
> +static int powernv_eeh_get_pe_addr(struct eeh_pe *pe)
> +{
> +	return pe->addr;
> +}
>
> +/**
> + * powernv_eeh_get_state - Retrieve PE state
> + * @pe: EEH PE
> + * @state: return value
> + *
> + * Retrieve the state of the specified PE. For IODA-compitable
> + * platform, it should be retrieved from IODA table. Therefore,
> + * we prefer passing down to hardware implementation to handle
> + * it.
> + */
> +static int powernv_eeh_get_state(struct eeh_pe *pe, int *state)
> +{
> +	struct pci_controller *hose = pe->phb;
> +	struct pnv_phb *phb = hose->private_data;
> +	int ret = EEH_STATE_NOT_SUPPORT;
> +
> +	if (phb->eeh_ops && phb->eeh_ops->get_state)
> +		ret = phb->eeh_ops->get_state(pe, state);
> +
> +	return ret;
> +}

Same comments about "state" which is really "delay" and is probably
not necessary at all ...

> +/**
> + * powernv_eeh_reset - Reset the specified PE
> + * @pe: EEH PE
> + * @option: reset option
> + *
> + * Reset the specified PE
> + */
> +static int powernv_eeh_reset(struct eeh_pe *pe, int option)
> +{
> +	struct pci_controller *hose = pe->phb;
> +	struct pnv_phb *phb = hose->private_data;
> +	int ret = -EEXIST;
> +
> +	if (phb->eeh_ops && phb->eeh_ops->reset)
> +		ret = phb->eeh_ops->reset(pe, option);
> +
> +	return ret;
> +}
> +
> +/**
> + * powernv_eeh_wait_state - Wait for PE state
> + * @pe: EEH PE
> + * @max_wait: maximal period in microsecond
> + *
> + * Wait for the state of associated PE. It might take some time
> + * to retrieve the PE's state.
> + */
> +static int powernv_eeh_wait_state(struct eeh_pe *pe, int max_wait)
> +{
> +	int ret;
> +	int mwait;
> +
> +	while (1) {
> +		ret = powernv_eeh_get_state(pe, &mwait);
> +
> +		/*
> +		 * If the PE's state is temporarily unavailable,
> +		 * we have to wait for the specified time. Otherwise,
> +		 * the PE's state will be returned immediately.
> +		 */
> +		if (ret != EEH_STATE_UNAVAILABLE)
> +			return ret;

So here we do a compare, while ret is actually a bit mask ...

In fact, ret should be named state_mask or something like that for clarity
and you should do a bit test here. Also do you want to diffenciate
permanent unavailability from temp. unavailability ?

> +		max_wait -= mwait;

You decrement max_wait but never test it or use it. You probably mean to

  - Limit mwait to max_wait
  - If mwait is 0, return

> +		msleep(mwait);
> +	}
> +
> +	return EEH_STATE_NOT_SUPPORT;
> +}
> +
> +/**
> + * powernv_eeh_get_log - Retrieve error log
> + * @pe: EEH PE
> + * @severity: temporary or permanent error log
> + * @drv_log: driver log to be combined with retrieved error log
> + * @len: length of driver log
> + *
> + * Retrieve the temporary or permanent error from the PE.
> + */
> +static int powernv_eeh_get_log(struct eeh_pe *pe, int severity,
> +			char *drv_log, unsigned long len)
> +{
> +	struct pci_controller *hose = pe->phb;
> +	struct pnv_phb *phb = hose->private_data;
> +	int ret = -EEXIST;
> +
> +	if (phb->eeh_ops && phb->eeh_ops->get_log)
> +		ret = phb->eeh_ops->get_log(pe, severity, drv_log, len);
> +
> +	return ret;
> +}
> +
> +/**
> + * powernv_eeh_configure_bridge - Configure PCI bridges in the indicated PE
> + * @pe: EEH PE
> + *
> + * The function will be called to reconfigure the bridges included
> + * in the specified PE so that the mulfunctional PE would be recovered
> + * again.
> + */
> +static int powernv_eeh_configure_bridge(struct eeh_pe *pe)
> +{
> +	struct pci_controller *hose = pe->phb;
> +	struct pnv_phb *phb = hose->private_data;
> +	int ret = 0;
> +
> +	if (phb->eeh_ops && phb->eeh_ops->configure_bridge)
> +		ret = phb->eeh_ops->configure_bridge(pe);
> +
> +	return ret;
> +}

Ben.