Re: [PATCH 02/11] omap2/3: Fix DEBUG_LL for omap zoom2/3

[Tony Lindgren <tony@atomide.com>]

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* Kevin Hilman <khilman@deeprootsystems.com> [100430 17:05]:
> Tony Lindgren <tony@atomide.com> writes:
> 
> > * Kevin Hilman <khilman@deeprootsystems.com> [100430 14:56]:
> >> "Pandita, Vikram" <vikram.pandita@ti.com> writes:
> >> >
> >> > So for Tony's approach to work, .phys_io/.io_pg_offset continued to
> >> > have 0x4800000 based mapping and for external uart zoom3 port,
> >> > create this extra mapping.
> >> >
> >> > So find a better way from compressed.S to pass the uart number to
> >> > kernel, and we can solve the problem.
> >> 
> >> Ah, yet another reason to use a memory location instead of UART1 SCR
> >> to pass the UART info (c.f. [1])
> >
> > That should work if we don't need to access any L4 registers
> > early on before .map_io.
> 
> I'd say if we're accessing L4 regs before .map_io, it's a bug that
> needs to be fixed, but I don't think we are.  If we were, we'd notice
> a hang when !CONFIG_DEBUG_LL since the .phys_io and .io_pg_offst are
> only mapped in when CONFIG_DEBUG_LL=y.

Yeah the current approach uses both, but only when CONFIG_DEBUG_LL=y
as you noted.
 
> I think we've been using .phys_io/.io_pg_offset incorrectly in OMAP as
> an early mapping of all the IO space, when it is intended just for use
> as early UART access, indicated by the comments in head.S and the
> fact that it's only used when CONFIG_DEBUG_LL=y

That's probably just a left over from when we could map L3 and L4 with
one mapping..

Anyways, here's an experimental patch for using a memory address instead
of UART1 for storing the debug port configuration in uncompress.h.

So far only tested on n900, will give it a try also on zoom3 after
updating the zoom3 related patch.

Now the real question is: Is it safe to use the fixed memory address?

#define OMAP_UART_INFO	(PHYS_OFFSET + 0x3ff8)

Also, another thing that needs to be checked is what happens if nothing
calls printk early and the debug port address configuration is not
set early.. Needs to be tested by adding printascii call only later
on.

Regards,

Tony

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>From c957c9a19fb5b53c2cff4f3bc5c9481f9a4a99aa Mon Sep 17 00:00:00 2001
From: Tony Lindgren <tony@atomide.com>
Date: Fri, 30 Apr 2010 17:39:19 -0700
Subject: [PATCH] omap: Use a memory address for storing the debug port info instead of UART1

This removes the dependency to the UART1 being
available for storing the debug configuration in
uncompress.h.

As suggested by Cyril Chemparathy <cyril@ti.com>,
Vikram Pandita <vikram.pandita@ti.com> and
Kevin Hilman <khilman@deeprootsystems.com>.

Signed-off-by: Tony Lindgren <tony@atomide.com>

diff --git a/arch/arm/mach-omap1/include/mach/debug-macro.S b/arch/arm/mach-omap1/include/mach/debug-macro.S
index b6d9584..e8a8cf3 100644
--- a/arch/arm/mach-omap1/include/mach/debug-macro.S
+++ b/arch/arm/mach-omap1/include/mach/debug-macro.S
@@ -13,6 +13,8 @@
 
 #include <linux/serial_reg.h>
 
+#include <asm/memory.h>
+
 #include <plat/serial.h>
 
 		.pushsection .data
@@ -37,23 +39,12 @@ omap_uart_virt:	.word	0x0
 		cmp	\rx, #0			@ is port configured?
 		bne	99f			@ already configured
 
-		/* Check 7XX UART1 scratchpad register for uart to use */
+		/* Check the debug UART configuration set in uncompress.h */
 		mrc	p15, 0, \rx, c1, c0
 		tst	\rx, #1			@ MMU enabled?
-		moveq	\rx, #0xff000000	@ physical base address
-		movne	\rx, #0xfe000000	@ virtual base
-		orr	\rx, \rx, #0x00fb0000	@ OMAP1UART1
-		ldrb	\rx, [\rx, #(UART_SCR << OMAP7XX_PORT_SHIFT)]
-		cmp	\rx, #0			@ anything in 7XX scratchpad?
-		bne	10f			@ found 7XX uart
-
-		/* Check 15xx/16xx UART1 scratchpad register for uart to use */
-		mrc	p15, 0, \rx, c1, c0
-		tst	\rx, #1			@ MMU enabled?
-		moveq	\rx, #0xff000000	@ physical base address
-		movne	\rx, #0xfe000000	@ virtual base
-		orr	\rx, \rx, #0x00fb0000	@ OMAP1UART1
-		ldrb	\rx, [\rx, #(UART_SCR << OMAP_PORT_SHIFT)]
+		ldreq	\rx, =OMAP_UART_INFO
+		ldrne	\rx, =__phys_to_virt(OMAP_UART_INFO)
+		ldr	\rx, [\rx, #0]
 
 		/* Select the UART to use based on the UART1 scratchpad value */
 10:		cmp	\rx, #0			@ no port configured?
diff --git a/arch/arm/mach-omap2/include/mach/debug-macro.S b/arch/arm/mach-omap2/include/mach/debug-macro.S
index 4a63a2e..4976169 100644
--- a/arch/arm/mach-omap2/include/mach/debug-macro.S
+++ b/arch/arm/mach-omap2/include/mach/debug-macro.S
@@ -13,6 +13,8 @@
 
 #include <linux/serial_reg.h>
 
+#include <asm/memory.h>
+
 #include <plat/serial.h>
 
 #define UART_OFFSET(addr)	((addr) & 0x00ffffff)
@@ -40,13 +42,12 @@ omap_uart_lsr:	.word	0
 		cmp	\rx, #0			@ is port configured?
 		bne	99f			@ already configured
 
-		/* Check UART1 scratchpad register for uart to use */
+		/* Check the debug UART configuration set in uncompress.h */
 		mrc	p15, 0, \rx, c1, c0
 		tst	\rx, #1			@ MMU enabled?
-		moveq	\rx, #0x48000000	@ physical base address
-		movne	\rx, #0xfa000000	@ virtual base
-		orr	\rx, \rx, #0x0006a000	@ uart1 on omap2/3/4
-		ldrb	\rx, [\rx, #(UART_SCR << OMAP_PORT_SHIFT)] @ scratchpad
+		ldreq	\rx, =OMAP_UART_INFO
+		ldrne	\rx, =__phys_to_virt(OMAP_UART_INFO)
+		ldr	\rx, [\rx, #0]
 
 		/* Select the UART to use based on the UART1 scratchpad value */
 		cmp	\rx, #0			@ no port configured?
diff --git a/arch/arm/plat-omap/include/plat/serial.h b/arch/arm/plat-omap/include/plat/serial.h
index 83dce4c..20c27b9 100644
--- a/arch/arm/plat-omap/include/plat/serial.h
+++ b/arch/arm/plat-omap/include/plat/serial.h
@@ -15,6 +15,8 @@
 
 #include <linux/init.h>
 
+#define OMAP_UART_INFO		(PHYS_OFFSET + 0x3ff8)
+
 /* OMAP1 serial ports */
 #define OMAP1_UART1_BASE	0xfffb0000
 #define OMAP1_UART2_BASE	0xfffb0800
diff --git a/arch/arm/plat-omap/include/plat/uncompress.h b/arch/arm/plat-omap/include/plat/uncompress.h
index 81d9ec5..44478f7 100644
--- a/arch/arm/plat-omap/include/plat/uncompress.h
+++ b/arch/arm/plat-omap/include/plat/uncompress.h
@@ -20,27 +20,22 @@
 #include <linux/types.h>
 #include <linux/serial_reg.h>
 
+#include <asm/memory.h>
+#include <asm/io.h>
 #include <asm/mach-types.h>
 
 #include <plat/serial.h>
 
-static volatile u8 *uart1_base;
-static int uart1_shift;
-
 static volatile u8 *uart_base;
 static int uart_shift;
 
 /*
- * Store the DEBUG_LL uart number into UART1 scratchpad register.
+ * Store the DEBUG_LL uart number into memory.
  * See also debug-macro.S, and serial.c for related code.
- *
- * Please note that we currently assume that:
- * - UART1 clocks are enabled for register access
- * - UART1 scratchpad register can be used
  */
-static void set_uart1_scratchpad(unsigned char port)
+static void set_omap_uart_info(unsigned char port)
 {
-	uart1_base[UART_SCR << uart1_shift] = port;
+	*(volatile u32 *)OMAP_UART_INFO = port;
 }
 
 static void putc(int c)
@@ -60,42 +55,38 @@ static inline void flush(void)
 /*
  * Macros to configure UART1 and debug UART
  */
-#define _DEBUG_LL_ENTRY(mach, uart1_phys, uart1_shft,			\
-			dbg_uart, dbg_shft, dbg_id)			\
+#define _DEBUG_LL_ENTRY(mach, dbg_uart, dbg_shft, dbg_id)		\
 	if (machine_is_##mach()) {					\
-		uart1_base = (volatile u8 *)(uart1_phys);		\
-		uart1_shift = (uart1_shft);				\
 		uart_base = (volatile u8 *)(dbg_uart);			\
 		uart_shift = (dbg_shft);				\
 		port = (dbg_id);					\
-		set_uart1_scratchpad(port);				\
+		set_omap_uart_info(port);				\
 		break;							\
 	}
 
 #define DEBUG_LL_OMAP7XX(p, mach)					\
-	_DEBUG_LL_ENTRY(mach, OMAP1_UART1_BASE, OMAP7XX_PORT_SHIFT,	\
-		OMAP1_UART##p##_BASE, OMAP7XX_PORT_SHIFT, OMAP1UART##p)
+	_DEBUG_LL_ENTRY(mach, OMAP1_UART##p##_BASE, OMAP7XX_PORT_SHIFT,	\
+		OMAP1UART##p)
 
 #define DEBUG_LL_OMAP1(p, mach)						\
-	_DEBUG_LL_ENTRY(mach, OMAP1_UART1_BASE, OMAP_PORT_SHIFT,	\
-		OMAP1_UART##p##_BASE, OMAP_PORT_SHIFT, OMAP1UART##p)
+	_DEBUG_LL_ENTRY(mach, OMAP1_UART##p##_BASE, OMAP_PORT_SHIFT,	\
+		OMAP1UART##p)
 
 #define DEBUG_LL_OMAP2(p, mach)						\
-	_DEBUG_LL_ENTRY(mach, OMAP2_UART1_BASE, OMAP_PORT_SHIFT,	\
-		OMAP2_UART##p##_BASE, OMAP_PORT_SHIFT, OMAP2UART##p)
+	_DEBUG_LL_ENTRY(mach, OMAP2_UART##p##_BASE, OMAP_PORT_SHIFT,	\
+		OMAP2UART##p)
 
 #define DEBUG_LL_OMAP3(p, mach)						\
-	_DEBUG_LL_ENTRY(mach, OMAP3_UART1_BASE, OMAP_PORT_SHIFT,	\
-		OMAP3_UART##p##_BASE, OMAP_PORT_SHIFT, OMAP3UART##p)
+	_DEBUG_LL_ENTRY(mach, OMAP3_UART##p##_BASE, OMAP_PORT_SHIFT,	\
+		OMAP3UART##p)
 
 #define DEBUG_LL_OMAP4(p, mach)						\
-	_DEBUG_LL_ENTRY(mach, OMAP4_UART1_BASE, OMAP_PORT_SHIFT,	\
-		OMAP4_UART##p##_BASE, OMAP_PORT_SHIFT, OMAP4UART##p)
+	_DEBUG_LL_ENTRY(mach, OMAP4_UART##p##_BASE, OMAP_PORT_SHIFT,	\
+		OMAP4UART##p)
 
 /* Zoom2/3 shift is different for UART1 and external port */
 #define DEBUG_LL_ZOOM(mach)						\
-	_DEBUG_LL_ENTRY(mach, OMAP2_UART1_BASE, OMAP_PORT_SHIFT,	\
-		ZOOM_UART_BASE, ZOOM_PORT_SHIFT, ZOOM_UART)
+	_DEBUG_LL_ENTRY(mach, ZOOM_UART_BASE, ZOOM_PORT_SHIFT, ZOOM_UART)
 
 static inline void __arch_decomp_setup(unsigned long arch_id)
 {