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From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [PATCH v2 2/2] powerpc/83xx: map IMMR with a BAT.
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>, oss@buserror.net,
        galak@kernel.crashing.org
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Date:   Mon, 16 Sep 2019 06:42:56 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On mpc83xx with a QE, IMMR is 2Mbytes and aligned on 2Mbytes boundarie.
On mpc83xx without a QE, IMMR is 1Mbyte and 1Mbyte aligned.

Each driver will map a part of it to access the registers it needs.
Some drivers will map the same part of IMMR as other drivers.

In order to reduce TLB misses, map the full IMMR with a BAT. If it is
2Mbytes aligned, map 2Mbytes. If there is no QE, the upper part will
remain unused, but it doesn't harm as it is mapped as guarded memory.

When the IMMR is not aligned on a 2Mbytes boundarie, only map 1Mbyte.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

---
v2:
- use a fixmap area instead of playing with ioremap_bot
- always map 2M unless IMMRBAR is only 1M aligned
---
 arch/powerpc/include/asm/fixmap.h  |  8 ++++++++
 arch/powerpc/platforms/83xx/misc.c | 11 +++++++++++
 2 files changed, 19 insertions(+)

diff --git a/arch/powerpc/include/asm/fixmap.h b/arch/powerpc/include/asm/fixmap.h
index 0cfc365d814b..79c3aa55f43d 100644
--- a/arch/powerpc/include/asm/fixmap.h
+++ b/arch/powerpc/include/asm/fixmap.h
@@ -15,6 +15,7 @@
 #define _ASM_FIXMAP_H
 
 #ifndef __ASSEMBLY__
+#include <linux/sizes.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
 #ifdef CONFIG_HIGHMEM
@@ -63,6 +64,13 @@ enum fixed_addresses {
 	FIX_IMMR_BASE = __ALIGN_MASK(FIX_IMMR_START, FIX_IMMR_SIZE - 1) - 1 +
 		       FIX_IMMR_SIZE,
 #endif
+#ifdef CONFIG_PPC_83xx
+	/* For IMMR we need an aligned 2M area */
+#define FIX_IMMR_SIZE	(SZ_2M / PAGE_SIZE)
+	FIX_IMMR_START,
+	FIX_IMMR_BASE = __ALIGN_MASK(FIX_IMMR_START, FIX_IMMR_SIZE - 1) - 1 +
+		       FIX_IMMR_SIZE,
+#endif
 	/* FIX_PCIE_MCFG, */
 	__end_of_fixed_addresses
 };
diff --git a/arch/powerpc/platforms/83xx/misc.c b/arch/powerpc/platforms/83xx/misc.c
index f46d7bf3b140..d08216e2002d 100644
--- a/arch/powerpc/platforms/83xx/misc.c
+++ b/arch/powerpc/platforms/83xx/misc.c
@@ -18,6 +18,8 @@
 #include <sysdev/fsl_soc.h>
 #include <sysdev/fsl_pci.h>
 
+#include <mm/mmu_decl.h>
+
 #include "mpc83xx.h"
 
 static __be32 __iomem *restart_reg_base;
@@ -145,6 +147,15 @@ void __init mpc83xx_setup_arch(void)
 	if (ppc_md.progress)
 		ppc_md.progress("mpc83xx_setup_arch()", 0);
 
+	if (!__map_without_bats) {
+		phys_addr_t immrbase = get_immrbase();
+		int immrsize = IS_ALIGNED(immrbase, SZ_2M) ? SZ_2M : SZ_1M;
+		unsigned long va = __fix_to_virt(FIX_IMMR_BASE);
+
+		setbat(-1, va, immrbase, immrsize, PAGE_KERNEL_NCG);
+		update_bats();
+	}
+
 	mpc83xx_setup_pci();
 }
 
-- 
2.13.3