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Date: Wed, 25 Sep 2013 14:59:22 -0700
From: Dan Williams <djbw@...com>
To: Jon Mason <jon.mason@...el.com>
Cc: Dave Jiang <dave.jiang@...el.com>,
Vinod Koul <vinod.koul@...el.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ioat: PM Support
On Wed, Aug 21, 2013 at 4:42 PM, Jon Mason <jon.mason@...el.com> wrote:
> Add power management support in the IOAT driver. Adding this feature
> resolves a known issue when attempting to suspend on systems with IOAT
> enabled. On those systems, IOAT would experience a DMA channel error
> when attempting to resume due to the channels not being suspended
> properly. Currently, all channels errors cause panics, thus bringing
> the system down.
>
> Unfortunately, a hardware errata needs to be worked around on Xeon IOAT
> devices. The channel cannot be suspended or reset if there are active
> XOR transactions. To get around this, check to see if XOR is enabled on
> the channel and the channel has pending transactions. If so, then grab
> the lock and wait for the queue to drain. It might be more elegant to
> see if there are any XOR operations pending in the list, but by that
> time the queue will have drained anyway.
>
> See BF509S in
> http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-c5500-c3500-spec-update.pdf
> See BT92 in
> http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-e5-family-spec-update.pdf
>
> Tested-by: Gary Hade <garyhade@...ibm.com>
> Signed-off-by: Jon Mason <jon.mason@...el.com>
> ---
> drivers/dma/ioat/dma.c | 1 +
> drivers/dma/ioat/dma.h | 1 +
> drivers/dma/ioat/dma_v2.c | 1 +
> drivers/dma/ioat/dma_v3.c | 60 ++++++++++++++++++++++++++++++++++++++++++---
> drivers/dma/ioat/pci.c | 39 +++++++++++++++++++++++++++++
> 5 files changed, 99 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/dma/ioat/dma.c b/drivers/dma/ioat/dma.c
> index 17a2393..44d5f3a 100644
> --- a/drivers/dma/ioat/dma.c
> +++ b/drivers/dma/ioat/dma.c
> @@ -1203,6 +1203,7 @@ int ioat1_dma_probe(struct ioatdma_device *device, int dca)
> device->self_test = ioat_dma_self_test;
> device->timer_fn = ioat1_timer_event;
> device->cleanup_fn = ioat1_cleanup_event;
> + device->suspend = ioat_suspend;
> dma = &device->common;
> dma->device_prep_dma_memcpy = ioat1_dma_prep_memcpy;
> dma->device_issue_pending = ioat1_dma_memcpy_issue_pending;
> diff --git a/drivers/dma/ioat/dma.h b/drivers/dma/ioat/dma.h
> index 54fb7b9..1372c8e 100644
> --- a/drivers/dma/ioat/dma.h
> +++ b/drivers/dma/ioat/dma.h
> @@ -97,6 +97,7 @@ struct ioatdma_device {
> void (*cleanup_fn)(unsigned long data);
> void (*timer_fn)(unsigned long data);
> int (*self_test)(struct ioatdma_device *device);
> + void (*suspend)(struct ioat_chan_common *chan);
> };
>
> struct ioat_chan_common {
> diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
> index b925e1b..bd21dcb 100644
> --- a/drivers/dma/ioat/dma_v2.c
> +++ b/drivers/dma/ioat/dma_v2.c
> @@ -890,6 +890,7 @@ int ioat2_dma_probe(struct ioatdma_device *device, int dca)
> device->cleanup_fn = ioat2_cleanup_event;
> device->timer_fn = ioat2_timer_event;
> device->self_test = ioat_dma_self_test;
> + device->suspend = ioat_suspend;
> dma = &device->common;
> dma->device_prep_dma_memcpy = ioat2_dma_prep_memcpy_lock;
> dma->device_issue_pending = ioat2_issue_pending;
> diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
> index a17ef21..2aaad1e 100644
> --- a/drivers/dma/ioat/dma_v3.c
> +++ b/drivers/dma/ioat/dma_v3.c
> @@ -653,12 +653,63 @@ static void ioat3_cleanup_event(unsigned long data)
> writew(IOAT_CHANCTRL_RUN, ioat->base.reg_base + IOAT_CHANCTRL_OFFSET);
> }
>
> +static inline void ioat3_suspend(struct ioat_chan_common *chan)
No need for inline.
> +{
> + struct pci_dev *pdev = to_pdev(chan);
> + struct dma_device *dma = &chan->device->common;
> + struct ioat2_dma_chan *ioat = container_of(chan, struct ioat2_dma_chan,
> + base);
> +
> + /* Due to HW errata on Xeon, we must make sure to flush the device prior
> + * to suspend or reset of the device if there are any XOR operations
> + * pending. Instead of inspecting the pending operations, just flush it
> + * if the channel supports XOR.
> + */
> + if (is_xeon_cb32(pdev) && dma_has_cap(DMA_XOR, dma->cap_mask) &&
Given this is always false in current kernels (admittedly not at the
time you originally sent the patch) I think we can delete this. There
may still be cases where we want to force enable xor but at that point
we should fail the suspend.
> + is_ioat_active(ioat_chansts(chan))) {
> + unsigned long end = jiffies + msecs_to_jiffies(100);
> +
> + spin_lock_bh(&ioat->prep_lock);
> + while (is_ioat_active(ioat_chansts(chan))) {
> + if (time_after(jiffies, end)) {
> + dev_err(&pdev->dev, "Timeout trying to suspend");
> + break;
> + }
> + cpu_relax();
> + }
> + ioat_suspend(chan);
> + spin_unlock_bh(&ioat->prep_lock);
> + } else
> + ioat_suspend(chan);
> +}
> +
> +static int ioat3_quiesce(struct ioat_chan_common *chan, unsigned long tmo)
> +{
> + unsigned long end = jiffies + tmo;
> + int err = 0;
> + u32 status;
> +
> + status = ioat_chansts(chan);
> + if (is_ioat_active(status) || is_ioat_idle(status))
> + ioat3_suspend(chan);
this can just be chan->device->suspend and if that happens this
routine can be replaced with ioat2_quiesce
> + while (is_ioat_active(status) || is_ioat_idle(status)) {
> + if (tmo && time_after(jiffies, end)) {
> + err = -ETIMEDOUT;
> + break;
> + }
> + status = ioat_chansts(chan);
> + cpu_relax();
> + }
> +
> + return err;
> +}
> +
> static void ioat3_restart_channel(struct ioat2_dma_chan *ioat)
> {
> struct ioat_chan_common *chan = &ioat->base;
> u64 phys_complete;
>
> - ioat2_quiesce(chan, 0);
> + ioat3_quiesce(chan, 0);
per-above I think we can ioat2_quiesce to do the right thing.
> if (ioat3_cleanup_preamble(chan, &phys_complete))
> __cleanup(ioat, phys_complete);
>
> @@ -1793,7 +1844,7 @@ static int ioat3_reset_hw(struct ioat_chan_common *chan)
> u16 dev_id;
> int err;
>
> - ioat2_quiesce(chan, msecs_to_jiffies(100));
> + ioat3_quiesce(chan, msecs_to_jiffies(100));
>
> chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
> writel(chanerr, chan->reg_base + IOAT_CHANERR_OFFSET);
> @@ -1873,6 +1924,7 @@ int ioat3_dma_probe(struct ioatdma_device *device, int dca)
> device->reset_hw = ioat3_reset_hw;
> device->self_test = ioat3_dma_self_test;
> device->intr_quirk = ioat3_intr_quirk;
> + device->suspend = ioat3_suspend;
> dma = &device->common;
> dma->device_prep_dma_memcpy = ioat2_dma_prep_memcpy_lock;
> dma->device_issue_pending = ioat2_issue_pending;
> @@ -1891,8 +1943,10 @@ int ioat3_dma_probe(struct ioatdma_device *device, int dca)
> device->cap &= ~(IOAT_CAP_XOR | IOAT_CAP_PQ | IOAT_CAP_RAID16SS);
>
> /* dca is incompatible with raid operations */
> - if (dca_en && (device->cap & (IOAT_CAP_XOR|IOAT_CAP_PQ)))
> + if (dca_en && (device->cap & (IOAT_CAP_XOR|IOAT_CAP_PQ))) {
> + pr_info("%s: DCA enabled, disabling XOR\n", __func__);
> device->cap &= ~(IOAT_CAP_XOR|IOAT_CAP_PQ);
> + }
>
> if (device->cap & IOAT_CAP_XOR) {
> is_raid_device = true;
> diff --git a/drivers/dma/ioat/pci.c b/drivers/dma/ioat/pci.c
> index 2c8d560..136b10a 100644
> --- a/drivers/dma/ioat/pci.c
> +++ b/drivers/dma/ioat/pci.c
> @@ -126,11 +126,50 @@ struct kmem_cache *ioat2_cache;
>
> #define DRV_NAME "ioatdma"
>
> +#ifdef CONFIG_PM
> +static int ioat_pm_suspend(struct device *dev)
> +{
> + struct pci_dev *pdev = to_pci_dev(dev);
> + struct ioatdma_device *device = pci_get_drvdata(pdev);
> + struct dma_device *dma = &device->common;
> + struct dma_chan *chan;
> +
> + list_for_each_entry(chan, &dma->channels, device_node) {
> + struct ioat_dma_chan *ioat = to_ioat_chan(chan);
> +
> + dev_info(dev, "Suspending Chan %d\n", chan->chan_id);
> + if (device->suspend)
> + device->suspend(&ioat->base);
I think we should modify this to fail to suspend if the implementation
does not have a suspend routine, and allow ->suspend to return an
error (no point in timing out if it does not block the suspend).
> + }
> +
> + return 0;
> +}
> +
> +static int ioat_pm_resume(struct device *dev)
> +{
> + struct pci_dev *pdev = to_pci_dev(dev);
> + struct ioatdma_device *device = pci_get_drvdata(pdev);
> + struct dma_device *dma = &device->common;
> + struct dma_chan *chan;
> +
> + list_for_each_entry(chan, &dma->channels, device_node) {
> + struct ioat_dma_chan *ioat = to_ioat_chan(chan);
> + dev_info(dev, "Starting Chan %d\n", chan->chan_id);
> + ioat_start(&ioat->base);
> + }
> +
> + return 0;
> +}
> +#endif
> +
> +SIMPLE_DEV_PM_OPS(ioat_pm_ops, ioat_pm_suspend, ioat_pm_resume);
> +
> static struct pci_driver ioat_pci_driver = {
> .name = DRV_NAME,
> .id_table = ioat_pci_tbl,
> .probe = ioat_pci_probe,
> .remove = ioat_remove,
> + .driver.pm = &ioat_pm_ops,
> };
>
> static struct ioatdma_device *
> --
> 1.7.9.5
>
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