ARM: 9004/1: debug: Split waituart to CTS and TXRDY

This patch was triggered by a remark from Russell that
introducing a call to the waituart (needed to fix debug prints
on the Qualcomm platforms) was dangerous because in some cases
this will involve waiting for a modem CTS (clear to send)
signal, and debug messages would maybe not work on platforms
with no modem connected to the UART port: they will just
hang waiting for the modem to assert CTS and this might never
happen.

Looking through all UART debug drivers implementing the waituart
macro I discovered that all users except two actually use this
macro to check if the UART is ready for TX, let's call this
TXRDY.

Only two debug UART drivers actually check for CTS:
- arch/arm/include/debug/8250.S
- arch/arm/include/debug/tegra.S

The former is very significant since the 8250 is possibly
the most common UART on the planet.

We have the following problem: the semantics of waituart are
ambiguous making it dangerous to introduce the macro to debug
code fixing debug prints for Qualcomm. To start to pry this
problem apart, this patch does the following:

- Convert all debug UART drivers to define two macros:

  - waituartcts with the clear semantic to wait for CTS
    to be asserted

  - waituarttxrdy with the clear semantic to wait for the TX
    capability of the UART to be ready

- When doing this take care to assign the right function to
  each drivers macro, so they now do exactly the above.

- Update the three sites in the kernel invoking the waituart
  macro to call waituartcts/waituarttxrdy in sequence, so that
  the functional impact on the kernel should be zero.

After this we can start to change the code sites using this
code to do the right thing.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

arch/arm/boot/compressed/debug.S

@@ -8,7 +8,8 @@
 
 ENTRY(putc)
 	addruart r1, r2, r3
-	waituart r3, r1
+	waituartcts r3, r1
+	waituarttxrdy r3, r1
 	senduart r0, r1
 	busyuart r3, r1
 	mov	 pc, lr

arch/arm/include/debug/8250.S

@@ -45,7 +45,10 @@
 		bne	1002b
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituarttxrdy,rd,rx
+		.endm
+
+		.macro	waituartcts,rd,rx
 #ifdef CONFIG_DEBUG_UART_8250_FLOW_CONTROL
 1001:		load	\rd, [\rx, #UART_MSR << UART_SHIFT]
 		tst	\rd, #UART_MSR_CTS

arch/arm/include/debug/asm9260.S

@@ -11,7 +11,10 @@
 		ldr	\rv, = CONFIG_DEBUG_UART_VIRT
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituarttxrdy,rd,rx
+		.endm
+
+		.macro	waituartcts,rd,rx
 		.endm
 
 		.macro	senduart,rd,rx

arch/arm/include/debug/at91.S

@@ -19,12 +19,15 @@
 	strb	\rd, [\rx, #(AT91_DBGU_THR)]		@ Write to Transmitter Holding Register
 	.endm
 
-	.macro	waituart,rd,rx
+	.macro	waituarttxrdy,rd,rx
 1001:	ldr	\rd, [\rx, #(AT91_DBGU_SR)]		@ Read Status Register
 	tst	\rd, #AT91_DBGU_TXRDY			@ DBGU_TXRDY = 1 when ready to transmit
 	beq	1001b
 	.endm
 
+	.macro	waituartcts,rd,rx
+	.endm
+
 	.macro	busyuart,rd,rx
 1001:	ldr	\rd, [\rx, #(AT91_DBGU_SR)]		@ Read Status Register
 	tst	\rd, #AT91_DBGU_TXEMPTY			@ DBGU_TXEMPTY = 1 when transmission complete

arch/arm/include/debug/bcm63xx.S

@@ -17,12 +17,15 @@
 	strb	\rd, [\rx, #UART_FIFO_REG]
 	.endm
 
-	.macro	waituart, rd, rx
+	.macro	waituarttxrdy, rd, rx
 1001:	ldr	\rd, [\rx, #UART_IR_REG]
 	tst	\rd, #(1 << UART_IR_TXEMPTY)
 	beq	1001b
 	.endm
 
+	.macro	waituartcts, rd, rx
+	.endm
+
 	.macro	busyuart, rd, rx
 1002:	ldr	\rd, [\rx, #UART_IR_REG]
 	tst	\rd, #(1 << UART_IR_TXTRESH)

arch/arm/include/debug/brcmstb.S

@@ -142,7 +142,10 @@ ARM_BE8(	rev	\rd, \rd )
 		bne	1002b
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituarttxrdy,rd,rx
+		.endm
+
+		.macro	waituartcts,rd,rx
 		.endm
 
 /*

arch/arm/include/debug/clps711x.S

@@ -20,7 +20,10 @@
 	ldr	\rp, =CLPS711X_UART_PADDR
 	.endm
 
-	.macro	waituart,rd,rx
+	.macro	waituartcts,rd,rx
+	.endm
+
+	.macro	waituarttxrdy,rd,rx
 	.endm
 
 	.macro	senduart,rd,rx

arch/arm/include/debug/dc21285.S

@@ -34,5 +34,8 @@
 		bne	1001b
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituartcts,rd,rx
+		.endm
+
+		.macro	waituarttxrdy,rd,rx
 		.endm

arch/arm/include/debug/digicolor.S

@@ -21,7 +21,10 @@
 		strb	\rd, [\rx, #UA0_EMI_REC]
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituartcts,rd,rx
+		.endm
+
+		.macro	waituarttxrdy,rd,rx
 		.endm
 
 	.macro	busyuart,rd,rx

arch/arm/include/debug/efm32.S

@@ -29,7 +29,10 @@
 		strb	\rd, [\rx, #UARTn_TXDATA]
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituartcts,rd,rx
+		.endm
+
+		.macro	waituarttxrdy,rd,rx
 1001:		ldr	\rd, [\rx, #UARTn_STATUS]
 		tst	\rd, #UARTn_STATUS_TXBL
 		beq	1001b

arch/arm/include/debug/icedcc.S

@@ -23,7 +23,10 @@
 		beq	1001b
 		.endm
 
-		.macro	waituart, rd, rx
+		.macro	waituartcts, rd, rx
+		.endm
+
+		.macro	waituarttxrdy, rd, rx
 		mov	\rd, #0x2000000
 1001:
 		subs	\rd, \rd, #1
@@ -47,7 +50,10 @@
 		beq	1001b
 		.endm
 
-		.macro	waituart, rd, rx
+		.macro	waituartcts, rd, rx
+		.endm
+
+		.macro	waituarttxrdy, rd, rx
 		mov	\rd, #0x10000000
 1001:
 		subs	\rd, \rd, #1
@@ -72,7 +78,10 @@
 
 		.endm
 
-		.macro	waituart, rd, rx
+		.macro	waituartcts, rd, rx
+		.endm
+
+		.macro	waituarttxrdy, rd, rx
 		mov	\rd, #0x2000000
 1001:
 		subs	\rd, \rd, #1

arch/arm/include/debug/imx.S

@@ -35,7 +35,10 @@
 		str	\rd, [\rx, #0x40]	@ TXDATA
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituartcts,rd,rx
+		.endm
+
+		.macro	waituarttxrdy,rd,rx
 		.endm
 
 		.macro	busyuart,rd,rx

arch/arm/include/debug/meson.S

@@ -25,7 +25,10 @@
 	beq	1002b
 	.endm
 
-	.macro	waituart,rd,rx
+	.macro	waituartcts,rd,rx
+	.endm
+
+	.macro	waituarttxrdy,rd,rx
 1001:	ldr	\rd, [\rx, #MESON_AO_UART_STATUS]
 	tst	\rd, #MESON_AO_UART_TX_FIFO_FULL
 	bne	1001b

arch/arm/include/debug/msm.S

@@ -17,7 +17,10 @@ ARM_BE8(rev	\rd, \rd )
 	str	\rd, [\rx, #0x70]
 	.endm
 
-	.macro	waituart, rd, rx
+	.macro	waituartcts,rd,rx
+	.endm
+
+	.macro	waituarttxrdy, rd, rx
 	@ check for TX_EMT in UARTDM_SR
 	ldr	\rd, [\rx, #0x08]
 ARM_BE8(rev     \rd, \rd )

arch/arm/include/debug/omap2plus.S

@@ -75,5 +75,8 @@ omap_uart_lsr:	.word	0
 		bne	1001b
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituartcts,rd,rx
+		.endm
+
+		.macro	waituarttxrdy,rd,rx
 		.endm

arch/arm/include/debug/pl01x.S

@@ -26,7 +26,10 @@
 		strb	\rd, [\rx, #UART01x_DR]
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituartcts,rd,rx
+		.endm
+
+		.macro	waituarttxrdy,rd,rx
 1001:		ldr	\rd, [\rx, #UART01x_FR]
  ARM_BE8(	rev	\rd, \rd )
 		tst	\rd, #UART01x_FR_TXFF

arch/arm/include/debug/renesas-scif.S

@@ -33,7 +33,10 @@
 	ldr	\rv, =SCIF_VIRT
 	.endm
 
-	.macro	waituart, rd, rx
+	.macro	waituartcts,rd,rx
+	.endm
+
+	.macro	waituarttxrdy, rd, rx
 1001:	ldrh	\rd, [\rx, #FSR]
 	tst	\rd, #TDFE
 	beq	1001b

arch/arm/include/debug/sa1100.S

@@ -51,7 +51,10 @@
 		str	\rd, [\rx, #UTDR]
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituartcts,rd,rx
+		.endm
+
+		.macro	waituarttxrdy,rd,rx
 1001:		ldr	\rd, [\rx, #UTSR1]
 		tst	\rd, #UTSR1_TNF
 		beq	1001b

arch/arm/include/debug/samsung.S

@@ -69,7 +69,10 @@ ARM_BE8(rev \rd, \rd)
 1002:		@ exit busyuart
 	.endm
 
-	.macro	waituart,rd,rx
+	.macro	waituartcts,rd,rx
+	.endm
+
+	.macro	waituarttxrdy,rd,rx
 		ldr	\rd, [\rx, # S3C2410_UFCON]
 ARM_BE8(rev \rd, \rd)
 		tst	\rd, #S3C2410_UFCON_FIFOMODE	@ fifo enabled?

arch/arm/include/debug/sirf.S

@@ -29,7 +29,10 @@
 	.macro	busyuart,rd,rx
 	.endm
 
-	.macro	waituart,rd,rx
+	.macro	waituartcts,rd,rx
+	.endm
+
+	.macro	waituarttxrdy,rd,rx
 1001:	ldr	\rd, [\rx, #SIRF_LLUART_TXFIFO_STATUS]
 	tst	\rd, #SIRF_LLUART_TXFIFO_EMPTY
 	beq	1001b

arch/arm/include/debug/sti.S

@@ -45,7 +45,10 @@
                 strb    \rd, [\rx, #ASC_TX_BUF_OFF]
                 .endm
 
-                .macro  waituart,rd,rx
+		.macro	waituartcts,rd,rx
+		.endm
+
+                .macro  waituarttxrdy,rd,rx
 1001:           ldr     \rd, [\rx, #ASC_STA_OFF]
                 tst     \rd, #ASC_STA_TX_FULL
                 bne     1001b

arch/arm/include/debug/stm32.S

@@ -27,7 +27,10 @@
 	strb    \rd, [\rx, #STM32_USART_TDR_OFF]
 .endm
 
-.macro  waituart,rd,rx
+.macro	waituartcts,rd,rx
+.endm
+
+.macro  waituarttxrdy,rd,rx
 1001:	ldr	\rd, [\rx, #(STM32_USART_SR_OFF)]	@ Read Status Register
 	tst	\rd, #STM32_USART_TXE			@ TXE = 1 = tx empty
 	beq	1001b

arch/arm/include/debug/tegra.S

@@ -178,7 +178,7 @@
 1002:
 		.endm
 
-		.macro	waituart, rd, rx
+		.macro	waituartcts, rd, rx
 #ifdef FLOW_CONTROL
 		cmp	\rx, #0
 		beq	1002f
@@ -189,6 +189,9 @@
 #endif
 		.endm
 
+		.macro	waituarttxrdy,rd,rx
+		.endm
+
 /*
  * Storage for the state maintained by the macros above.
  *

arch/arm/include/debug/vf.S

@@ -29,5 +29,8 @@
 	beq	1001b			@ wait until transmit done
 	.endm
 
-	.macro	waituart,rd,rx
+	.macro	waituartcts,rd,rx
+	.endm
+
+	.macro	waituarttxrdy,rd,rx
 	.endm

arch/arm/include/debug/vt8500.S

@@ -28,7 +28,10 @@
 	bne	1001b
 	.endm
 
-	.macro	waituart,rd,rx
+	.macro	waituartcts,rd,rx
+	.endm
+
+	.macro	waituarttxrdy,rd,rx
 	.endm
 
 #endif

arch/arm/include/debug/zynq.S

@@ -33,7 +33,10 @@
 		strb	\rd, [\rx, #UART_FIFO_OFFSET]	@ TXDATA
 		.endm
 
-		.macro	waituart,rd,rx
+		.macro	waituartcts,rd,rx
+		.endm
+
+		.macro	waituarttxrdy,rd,rx
 1001:		ldr	\rd, [\rx, #UART_SR_OFFSET]
 ARM_BE8(	rev	\rd, \rd )
 		tst	\rd, #UART_SR_TXEMPTY

arch/arm/kernel/debug.S

@@ -89,11 +89,13 @@ ENTRY(printascii)
 2:		teq     r1, #'\n'
 		bne	3f
 		mov	r1, #'\r'
-		waituart r2, r3
+		waituartcts r2, r3
+		waituarttxrdy r2, r3
 		senduart r1, r3
 		busyuart r2, r3
 		mov	r1, #'\n'
-3:		waituart r2, r3
+3:		waituartcts r2, r3
+		waituarttxrdy r2, r3
 		senduart r1, r3
 		busyuart r2, r3
 		b	1b