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From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [PATCH 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:   Fri, 23 Aug 2019 12:50:18 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On mpc83xx with a QE, IMMR is 2Mbytes.
On mpc83xx without a QE, IMMR is 1Mbytes.
Each driver will map a part of it to access the registers it needs.
Some driver will map the same part of IMMR as other drivers.

In order to reduce TLB misses, map the full IMMR with a BAT.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/platforms/83xx/misc.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/powerpc/platforms/83xx/misc.c b/arch/powerpc/platforms/83xx/misc.c
index f46d7bf3b140..1e395b01c535 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 +147,14 @@ void __init mpc83xx_setup_arch(void)
 	if (ppc_md.progress)
 		ppc_md.progress("mpc83xx_setup_arch()", 0);
 
+	if (!__map_without_bats) {
+		int immrsize = IS_ENABLED(CONFIG_QUICC_ENGINE) ? SZ_2M : SZ_1M;
+
+		ioremap_bot = ALIGN_DOWN(ioremap_bot - immrsize, immrsize);
+		setbat(-1, ioremap_bot, get_immrbase(), immrsize, PAGE_KERNEL_NCG);
+		update_bats();
+	}
+
 	mpc83xx_setup_pci();
 }
 
-- 
2.13.3