From: "David E. Box" <david.e.box@linux.intel.com>
Date: Wed, 20 Apr 2022 08:56:20 -0700
Subject: platform/x86/intel/sdsi: Handle leaky bucket
Git-commit: 679c7a3f1596e8b5493c9473da4d967de540027c
Patch-mainline: 5.18-rc5
References: jsc#SLE-18901
Alt-commit: 5d7e5e346ef84949db438e9ca1ef81d895b56c0f
To prevent an agent from indefinitely holding the mailbox firmware has
implemented a leaky bucket algorithm. Repeated access to the mailbox may
now incur a delay of up to 2.1 seconds. Add a retry loop that tries for
up to 2.5 seconds to acquire the mailbox.
Fixes: 2546c6000430 ("platform/x86: Add Intel Software Defined Silicon driver")
Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: https://lore.kernel.org/r/20220420155622.1763633-2-david.e.box@linux.intel.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
drivers/platform/x86/intel/sdsi.c | 32 +++++++++++++++++++++++++-------
1 file changed, 25 insertions(+), 7 deletions(-)
--- a/drivers/platform/x86/intel/sdsi.c
+++ b/drivers/platform/x86/intel/sdsi.c
@@ -51,6 +51,8 @@
#define MBOX_TIMEOUT_US 2000
#define MBOX_TIMEOUT_ACQUIRE_US 1000
#define MBOX_POLLING_PERIOD_US 100
+#define MBOX_ACQUIRE_NUM_RETRIES 5
+#define MBOX_ACQUIRE_RETRY_DELAY_MS 500
#define MBOX_MAX_PACKETS 4
#define MBOX_OWNER_NONE 0x00
@@ -263,7 +265,7 @@ static int sdsi_mbox_acquire(struct sdsi
{
u64 control;
u32 owner;
- int ret;
+ int ret, retries = 0;
lockdep_assert_held(&priv->mb_lock);
@@ -273,13 +275,29 @@ static int sdsi_mbox_acquire(struct sdsi
if (owner != MBOX_OWNER_NONE)
return -EBUSY;
- /* Write first qword of payload */
- writeq(info->payload[0], priv->mbox_addr);
+ /*
+ * If there has been no recent transaction and no one owns the mailbox,
+ * we should acquire it in under 1ms. However, if we've accessed it
+ * recently it may take up to 2.1 seconds to acquire it again.
+ */
+ do {
+ /* Write first qword of payload */
+ writeq(info->payload[0], priv->mbox_addr);
+
+ /* Check for ownership */
+ ret = readq_poll_timeout(priv->control_addr, control,
+ FIELD_GET(CTRL_OWNER, control) == MBOX_OWNER_INBAND,
+ MBOX_POLLING_PERIOD_US, MBOX_TIMEOUT_ACQUIRE_US);
+
+ if (FIELD_GET(CTRL_OWNER, control) == MBOX_OWNER_NONE &&
+ retries++ < MBOX_ACQUIRE_NUM_RETRIES) {
+ msleep(MBOX_ACQUIRE_RETRY_DELAY_MS);
+ continue;
+ }
- /* Check for ownership */
- ret = readq_poll_timeout(priv->control_addr, control,
- FIELD_GET(CTRL_OWNER, control) & MBOX_OWNER_INBAND,
- MBOX_POLLING_PERIOD_US, MBOX_TIMEOUT_ACQUIRE_US);
+ /* Either we got it or someone else did. */
+ break;
+ } while (true);
return ret;
}