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From: Thomas Bogendoerfer <tbogendoerfer@suse.de>
To: Ralf Baechle <ralf@linux-mips.org>,
	Paul Burton <paul.burton@mips.com>,
	James Hogan <jhogan@kernel.org>,
	linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 4/6] MIPS: fw: arc: workaround 64bit kernel/32bit ARC problems
Date: Wed,  9 Oct 2019 15:27:15 +0200	[thread overview]
Message-ID: <20191009132718.25346-5-tbogendoerfer@suse.de> (raw)
In-Reply-To: <20191009132718.25346-1-tbogendoerfer@suse.de>

Pointer arguments for 32bit ARC PROMs must reside in CKSEG0/1. While
the initial stack resides in CKSEG0 the first kernel thread stack
is already placed at a XKPHYS address, which ARC32 can't handle.
The workaround here is to use static variables, which are placed
into BSS and linked to a CKSEG0 address.

Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 arch/mips/fw/arc/promlib.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/arch/mips/fw/arc/promlib.c b/arch/mips/fw/arc/promlib.c
index be381307fbb0..5e9e840a9314 100644
--- a/arch/mips/fw/arc/promlib.c
+++ b/arch/mips/fw/arc/promlib.c
@@ -11,6 +11,21 @@
 #include <asm/bcache.h>
 #include <asm/setup.h>
 
+#if defined(CONFIG_64BIT) && defined(CONFIG_FW_ARC32)
+/*
+ * For 64bit kernels working with a 32bit ARC PROM pointer arguments
+ * for ARC calls need to reside in CKEG0/1. But as soon as the kernel
+ * switches to it's first kernel thread stack is set to an address in
+ * XKPHYS, so anything on stack can't be used anymore. This is solved
+ * by using a * static declartion variables are put into BSS, which is
+ * linked to a CKSEG0 address. Since this is only used on UP platforms
+ * there is not spinlock needed
+ */
+#define O32_STATIC	static
+#else
+#define O32_STATIC
+#endif
+
 /*
  * IP22 boardcache is not compatible with board caches.	 Thus we disable it
  * during romvec action.  Since r4xx0.c is always compiled and linked with your
@@ -23,8 +38,10 @@
 
 void prom_putchar(char c)
 {
-	ULONG cnt;
-	CHAR it = c;
+	O32_STATIC ULONG cnt;
+	O32_STATIC CHAR it;
+
+	it = c;
 
 	bc_disable();
 	ArcWrite(1, &it, 1, &cnt);
@@ -33,8 +50,8 @@ void prom_putchar(char c)
 
 char prom_getchar(void)
 {
-	ULONG cnt;
-	CHAR c;
+	O32_STATIC ULONG cnt;
+	O32_STATIC CHAR c;
 
 	bc_disable();
 	ArcRead(0, &c, 1, &cnt);
-- 
2.16.4


  parent reply	other threads:[~2019-10-09 13:27 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-09 13:27 [PATCH 0/6] Clean up ARC code and fix IP22/28 early printk Thomas Bogendoerfer
2019-10-09 13:27 ` [PATCH 1/6] MIPS: fw: arc: remove unused ARC code Thomas Bogendoerfer
2019-10-09 13:27 ` [PATCH 2/6] MIPS: fw: arc: use call_o32 to call ARC prom from 64bit kernel Thomas Bogendoerfer
2019-10-09 13:27 ` [PATCH 3/6] MIPS: Kconfig: always select ARC_MEMORY and ARC_PROMLIB for platform Thomas Bogendoerfer
2019-10-09 13:27 ` Thomas Bogendoerfer [this message]
2019-10-09 13:27 ` [PATCH 5/6] MIPS: SGI-IP22: set PHYS_OFFSET to memory start Thomas Bogendoerfer
2019-10-09 13:27 ` [PATCH 6/6] MIPS: SGI-IP22/28: Use PROM for memory detection Thomas Bogendoerfer
2019-10-09 21:58 ` [PATCH 0/6] Clean up ARC code and fix IP22/28 early printk Paul Burton

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