crypto: omap-sham - Fix Polling mode for larger blocks

Command "tcrypt sec=1 mode=403" give the follwoing error for Polling
mode:
root@am335x-evm:/# insmod tcrypt.ko sec=1 mode=403
[...]

[  346.982754] test 15 ( 4096 byte blocks, 1024 bytes per update,   4 updates):   4352 opers/sec,  17825792 bytes/sec
[  347.992661] test 16 ( 4096 byte blocks, 4096 bytes per update,   1 updates):   7095 opers/sec,  29061120 bytes/sec
[  349.002667] test 17 ( 8192 byte blocks,   16 bytes per update, 512 updates):
[  349.010882] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[  349.020037] pgd = ddeac000
[  349.022884] [00000000] *pgd=9dcb4831, *pte=00000000, *ppte=00000000
[  349.029816] Internal error: Oops: 17 [#1] PREEMPT SMP ARM
[  349.035482] Modules linked in: tcrypt(+)
[  349.039617] CPU: 0 PID: 1473 Comm: insmod Not tainted 3.12.4-01566-g6279006-dirty #38
[  349.047832] task: dda91540 ti: ddcd2000 task.ti: ddcd2000
[  349.053517] PC is at omap_sham_xmit_dma+0x6c/0x238
[  349.058544] LR is at omap_sham_xmit_dma+0x38/0x238
[  349.063570] pc : [<c04eb7cc>]    lr : [<c04eb798>]    psr: 20000013
[  349.063570] sp : ddcd3c78  ip : 00000000  fp : 9d8980b8
[  349.075610] r10: 00000000  r9 : 00000000  r8 : 00000000
[  349.081090] r7 : 00001000  r6 : dd898000  r5 : 00000040  r4 : ddb10550
[  349.087935] r3 : 00000004  r2 : 00000010  r1 : 53100080  r0 : 00000000
[  349.094783] Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
[  349.102268] Control: 10c5387d  Table: 9deac019  DAC: 00000015
[  349.108294] Process insmod (pid: 1473, stack limit = 0xddcd2248)

[...]

This is because polling_mode is not enabled for ctx without FLAGS_FINUP.

For polling mode the bufcnt is made 0 unconditionally. But it should be made 0
only if it is a final update or a total is not zero(This condition is similar
to what is done in DMA case). Because of this wrong hashes are produced.

Fixing the same.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/omap-sham.c

@@ -789,10 +789,13 @@ static int omap_sham_update_cpu(struct omap_sham_dev *dd)
 	dev_dbg(dd->dev, "cpu: bufcnt: %u, digcnt: %d, final: %d\n",
 		ctx->bufcnt, ctx->digcnt, final);
 
-	bufcnt = ctx->bufcnt;
-	ctx->bufcnt = 0;
+	if (final || (ctx->bufcnt == ctx->buflen && ctx->total)) {
+		bufcnt = ctx->bufcnt;
+		ctx->bufcnt = 0;
+		return omap_sham_xmit_cpu(dd, ctx->buffer, bufcnt, final);
+	}
 
-	return omap_sham_xmit_cpu(dd, ctx->buffer, bufcnt, final);
+	return 0;
 }
 
 static int omap_sham_update_dma_stop(struct omap_sham_dev *dd)
@@ -1103,6 +1106,9 @@ static int omap_sham_update(struct ahash_request *req)
 		return 0;
 	}
 
+	if (dd->polling_mode)
+		ctx->flags |= BIT(FLAGS_CPU);
+
 	return omap_sham_enqueue(req, OP_UPDATE);
 }