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From: John David Anglin <dave.anglin@bell.net>
To: linux-parisc <linux-parisc@vger.kernel.org>
Cc: Helge Deller <deller@gmx.de>,
	James Bottomley <James.Bottomley@HansenPartnership.com>
Subject: [PATCH] parisc: Use implicit space register selection for loading the coherence index of I/O pdirs
Date: Mon, 27 May 2019 20:15:14 -0400	[thread overview]
Message-ID: <f267f3ce-9baa-5e2f-1f0a-c08e59a53a7a@bell.net> (raw)

We only support I/O to kernel space.  Using %sr1 to load the coherence index
may be racy unless interrupts are disabled.  This patch changes the code used
to load the coherence index to use implicit space register selection.  This saves
one instruction and eliminates the race.

Tested on rp3440, c8000 and c3750.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
---

diff --git a/drivers/parisc/ccio-dma.c b/drivers/parisc/ccio-dma.c
index acba1f56af3e..d7649a70a0c4 100644
--- a/drivers/parisc/ccio-dma.c
+++ b/drivers/parisc/ccio-dma.c
@@ -565,8 +565,6 @@ ccio_io_pdir_entry(u64 *pdir_ptr, space_t sid, unsigned long vba,
 	/* We currently only support kernel addresses */
 	BUG_ON(sid != KERNEL_SPACE);

-	mtsp(sid,1);
-
 	/*
 	** WORD 1 - low order word
 	** "hints" parm includes the VALID bit!
@@ -597,7 +595,7 @@ ccio_io_pdir_entry(u64 *pdir_ptr, space_t sid, unsigned long vba,
 	** Grab virtual index [0:11]
 	** Deposit virt_idx bits into I/O PDIR word
 	*/
-	asm volatile ("lci %%r0(%%sr1, %1), %0" : "=r" (ci) : "r" (vba));
+	asm volatile ("lci %%r0(%1), %0" : "=r" (ci) : "r" (vba));
 	asm volatile ("extru %1,19,12,%0" : "+r" (ci) : "r" (ci));
 	asm volatile ("depw  %1,15,12,%0" : "+r" (pa) : "r" (ci));

diff --git a/drivers/parisc/sba_iommu.c b/drivers/parisc/sba_iommu.c
index 0a9c762a70fa..5468490d2298 100644
--- a/drivers/parisc/sba_iommu.c
+++ b/drivers/parisc/sba_iommu.c
@@ -575,8 +575,7 @@ sba_io_pdir_entry(u64 *pdir_ptr, space_t sid, unsigned long vba,
 	pa = virt_to_phys(vba);
 	pa &= IOVP_MASK;

-	mtsp(sid,1);
-	asm("lci 0(%%sr1, %1), %0" : "=r" (ci) : "r" (vba));
+	asm("lci 0(%1), %0" : "=r" (ci) : "r" (vba));
 	pa |= (ci >> PAGE_SHIFT) & 0xff;  /* move CI (8 bits) into lowest byte */

 	pa |= SBA_PDIR_VALID_BIT;	/* set "valid" bit */

             reply	other threads:[~2019-05-28  0:15 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-28  0:15 John David Anglin [this message]
2019-05-28  5:01 ` [PATCH] parisc: Use implicit space register selection for loading the coherence index of I/O pdirs Helge Deller
2019-05-28 12:18   ` John David Anglin

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