linux-kernel - Backlog support for CAAM?

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Date:   Wed, 24 Jul 2019 23:22:08 +0200 (CEST)
From:   Richard Weinberger <richard@....at>
To:     linux-crypto@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Cc:     horia.geanta@....com, aymen.sghaier@....com,
        david <david@...ma-star.at>
Subject: Backlog support for CAAM?

Hi!

Recently I had the pleasure to debug a lockup on a imx6 based platform.
It turned out that the lockup was caused by the CAAM driver because it
just returns -EBUSY upon a full job ring.

Then I found commits:
0618764cb25f ("dm crypt: fix deadlock when async crypto algorithm returns -EBUSY")
c0403ec0bb5a ("Revert "dm crypt: fix deadlock when async crypto algorithm returns -EBUSY"")

Is there a reason why the driver has still no proper backlog support?

If it is just a matter of -ENOPATCH, I have some cycles left an can help.
But before working on this topic I'd like to figure what the current state
or plans are. :-)

So far I work around the issue with disgusting hacks like this one:

--- a/drivers/crypto/caam/jr.c
+++ b/drivers/crypto/caam/jr.c
@@ -339,6 +339,7 @@ int caam_jr_enqueue(struct device *dev, u32 *desc,
                return -EIO;
        }
 
+again:
        spin_lock_bh(&jrp->inplock);
 
        head = jrp->head;
@@ -347,8 +348,8 @@ int caam_jr_enqueue(struct device *dev, u32 *desc,
        if (!rd_reg32(&jrp->rregs->inpring_avail) ||
            CIRC_SPACE(head, tail, JOBR_DEPTH) <= 0) {
                spin_unlock_bh(&jrp->inplock);
-               dma_unmap_single(dev, desc_dma, desc_size, DMA_TO_DEVICE);
-               return -EBUSY;
+               msleep(100);
+               goto again;
        }
 
        head_entry = &jrp->entinfo[head];

Thanks,
//richard