Re: [PATCH] bus: mhi: Disable IRQs instead of freeing them during power down

Qiang Yu <quic_qianyu@xxxxxxxxxxx> · Fri, 10 Jun 2022 11:21:05 +0800

On 6/9/2022 9:54 PM, Jeffrey Hugo wrote:

On 6/9/2022 7:43 AM, Qiang Yu wrote:
EP tends to read MSI address/data once and cache them after BME is set.
So host should avoid changing MSI address/data after BME is set.

In pci reset function, host invokes free_irq(), which also clears MSI
address/data in EP's PCIe config space. If the invalid address/data
are cached and used by EP, MSI triggered by EP wouldn't be received by
host, because an invalid MSI data is sent to an invalid MSI address.

To fix this issue, after host runs request_irq() successfully during
mhi driver probe, let's invoke enable_irq()/disable_irq() instead of
request_irq()/free_irq() when we want to power on and power down MHI.
Meanwhile, Host should invoke free_irq() when mhi host driver is
removed.

I don't think this works for hotplug, nor cases where there are 
multiple MHI devices on the system.

The EP shouldn't be caching this information for multiple reasons. 
Masking the MSIs, disabling the MSIs, changing the address when the 
affinity changes, etc.

It really feels like we are solving the problem in the wrong place.

Right now, this gets a NACK from me.

After free_irq(), MSI is still enabled but MSI address and data are 
cleared. So there is a chance that device initiates MSI using zero 
address. How to fix this race conditions.

Maybe EP should not cache MSI data and address. But I think this patch 
is necessary and we will talk with EP POC.


Signed-off-by: Qiang Yu <quic_qianyu@xxxxxxxxxxx>
---
  drivers/bus/mhi/host/init.c        | 31 
+++++++++++++++++++++++++++++++
  drivers/bus/mhi/host/pci_generic.c |  2 ++
  drivers/bus/mhi/host/pm.c          |  4 ++--
  3 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
index cbb86b2..48cb093 100644
--- a/drivers/bus/mhi/host/init.c
+++ b/drivers/bus/mhi/host/init.c
@@ -18,6 +18,7 @@
  #include <linux/slab.h>
  #include <linux/vmalloc.h>
  #include <linux/wait.h>
+#include <linux/irq.h>

Should be in alphabetical order

  #include "internal.h"
    static DEFINE_IDA(mhi_controller_ida);
@@ -168,6 +169,22 @@ int mhi_init_irq_setup(struct mhi_controller 
*mhi_cntrl)
      unsigned long irq_flags = IRQF_SHARED | IRQF_NO_SUSPEND;
      int i, ret;
  +    /*
+     * if irq[0] has action, it represents all MSI IRQs have been
+     * requested, so we just need to enable them.
+     */

This seems like an assumption about how the interrupts are allocated 
and assigned that may not hold true for all devices.

All interrupts are allocated and assigned together in mhi_pci_get_irqs() 
and mhi_init_irq_setup().

So I think if irq[0] has action, other irqs must be requested 
successfully. If any other msi request fail, irq[0] should have been freed.

+    if (irq_has_action(mhi_cntrl->irq[0])) {
+        enable_irq(mhi_cntrl->irq[0]);
+
+        for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
+            if (mhi_event->offload_ev)
+                continue;
+
+            enable_irq(mhi_cntrl->irq[mhi_event->irq]);
+        }
+        return 0;
+    }
+
      /* if controller driver has set irq_flags, use it */
      if (mhi_cntrl->irq_flags)
          irq_flags = mhi_cntrl->irq_flags;
@@ -179,6 +196,11 @@ int mhi_init_irq_setup(struct mhi_controller 
*mhi_cntrl)
                     "bhi", mhi_cntrl);
      if (ret)
          return ret;
+    /*
+     * IRQ marked IRQF_SHARED isn't recommended to use IRQ_NOAUTOEN,
+     * so disable it explicitly.
+     */
+    disable_irq(mhi_cntrl->irq[0]);
        for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
          if (mhi_event->offload_ev)
@@ -200,6 +222,8 @@ int mhi_init_irq_setup(struct mhi_controller 
*mhi_cntrl)
                  mhi_cntrl->irq[mhi_event->irq], i);
              goto error_request;
          }
+
+        disable_irq(mhi_cntrl->irq[mhi_event->irq]);
      }
        return 0;
@@ -1003,8 +1027,14 @@ int mhi_register_controller(struct 
mhi_controller *mhi_cntrl,
        mhi_create_debugfs(mhi_cntrl);
  +    ret = mhi_init_irq_setup(mhi_cntrl);
+    if (ret)
+        goto error_setup_irq;
+
      return 0;
  +error_setup_irq:
+    mhi_destroy_debugfs(mhi_cntrl);
  err_release_dev:
      put_device(&mhi_dev->dev);
  err_ida_free:
@@ -1027,6 +1057,7 @@ void mhi_unregister_controller(struct 
mhi_controller *mhi_cntrl)
      struct mhi_chan *mhi_chan = mhi_cntrl->mhi_chan;
      unsigned int i;
  +    mhi_deinit_free_irq(mhi_cntrl);
      mhi_destroy_debugfs(mhi_cntrl);
        destroy_workqueue(mhi_cntrl->hiprio_wq);
diff --git a/drivers/bus/mhi/host/pci_generic.c 
b/drivers/bus/mhi/host/pci_generic.c
index 6fbc591..60020d0 100644
--- a/drivers/bus/mhi/host/pci_generic.c
+++ b/drivers/bus/mhi/host/pci_generic.c
@@ -945,6 +945,8 @@ static void mhi_pci_remove(struct pci_dev *pdev)
        mhi_unregister_controller(mhi_cntrl);
      pci_disable_pcie_error_reporting(pdev);
+
+    pci_free_irq_vectors(pdev);
  }
    static void mhi_pci_shutdown(struct pci_dev *pdev)
diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
index dc2e8ff..190231c 100644
--- a/drivers/bus/mhi/host/pm.c
+++ b/drivers/bus/mhi/host/pm.c
@@ -500,7 +500,7 @@ static void mhi_pm_disable_transition(struct 
mhi_controller *mhi_cntrl)
      for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
          if (mhi_event->offload_ev)
              continue;
-        free_irq(mhi_cntrl->irq[mhi_event->irq], mhi_event);
+        disable_irq(mhi_cntrl->irq[mhi_event->irq]);
          tasklet_kill(&mhi_event->task);
      }
  @@ -1182,7 +1182,7 @@ void mhi_power_down(struct mhi_controller 
*mhi_cntrl, bool graceful)
      /* Wait for shutdown to complete */
      flush_work(&mhi_cntrl->st_worker);
  -    free_irq(mhi_cntrl->irq[0], mhi_cntrl);
+    disable_irq(mhi_cntrl->irq[0]);
  }
  EXPORT_SYMBOL_GPL(mhi_power_down);







