linux-kernel - [PATCH 3.16 46/87] parisc: Use implicit space register selection for loading the coherence index of I/O pdirs

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Message-ID: <lsq.1570043211.864935705@decadent.org.uk>
Date:   Wed, 02 Oct 2019 20:06:51 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Helge Deller" <deller@....de>,
        "John David Anglin" <dave.anglin@...l.net>
Subject: [PATCH 3.16 46/87] parisc: Use implicit space register selection
 for loading the coherence index of I/O pdirs

3.16.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: John David Anglin <dave.anglin@...l.net>

commit 63923d2c3800919774f5c651d503d1dd2adaddd5 upstream.

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@...l.net>
Signed-off-by: Helge Deller <deller@....de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/parisc/ccio-dma.c  | 4 +---
 drivers/parisc/sba_iommu.c | 3 +--
 2 files changed, 2 insertions(+), 5 deletions(-)

--- a/drivers/parisc/ccio-dma.c
+++ b/drivers/parisc/ccio-dma.c
@@ -563,8 +563,6 @@ ccio_io_pdir_entry(u64 *pdir_ptr, space_
 	/* 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!
@@ -595,7 +593,7 @@ ccio_io_pdir_entry(u64 *pdir_ptr, space_
 	** 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));
 
--- a/drivers/parisc/sba_iommu.c
+++ b/drivers/parisc/sba_iommu.c
@@ -573,8 +573,7 @@ sba_io_pdir_entry(u64 *pdir_ptr, space_t
 	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 */