Commit 679c7a3f authored by David E. Box's avatar David E. Box Committed by Hans de Goede
Browse files

platform/x86/intel/sdsi: Handle leaky bucket 



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: 2546c600 ("platform/x86: Add Intel Software Defined Silicon driver")
Signed-off-by: default avatarDavid 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: default avatarHans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
parent 8d75f7b4

drivers/platform/x86/intel/sdsi.c

+25 −7
Original line number Diff line number Diff line
@@ -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_priv *priv, struct sdsi_mbox_info *info 
{

	u64 control;

	u32 owner;

	int ret;

	int ret, retries = 0;



	lockdep_assert_held(&priv->mb_lock);
@@ -273,14 +275,30 @@ static int sdsi_mbox_acquire(struct sdsi_priv *priv, struct sdsi_mbox_info *info 
	if (owner != MBOX_OWNER_NONE)

		return -EBUSY;



	/*

	 * 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,

			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;

		}



		/* Either we got it or someone else did. */

		break;

	} while (true);



	return ret;

}