Disable PL011 UART before configuring it
The PL011 TRM (ARM DDI 0183G) specifies that the UART must be
disabled before any of the control registers are programmed. The
PL011 driver included in TF does not disable the UART, so the
initialization in BL2 and BL31 is violating this requirement
(and potentially in BL1 if the UART is enabled after reset).
This patch modifies the initialization function in the PL011
console driver to disable the UART before programming the
control registers.
Register clobber list and documentation updated.
Fixes ARM-software/tf-issues#300
Change-Id: I839b2d681d48b03f821ac53663a6a78e8b30a1a1
diff --git a/docs/porting-guide.md b/docs/porting-guide.md
index cdb722a..66d4121 100644
--- a/docs/porting-guide.md
+++ b/docs/porting-guide.md
@@ -1860,7 +1860,7 @@
Return : int
This API is used by the crash reporting mechanism to initialize the crash
-console. It should only use the general purpose registers x0 to x2 to do the
+console. It must only use the general purpose registers x0 to x4 to do the
initialization and returns 1 on success.
### Function : plat_crash_console_putc
@@ -1869,7 +1869,7 @@
Return : int
This API is used by the crash reporting mechanism to print a character on the
-designated crash console. It should only use general purpose registers x1 and
+designated crash console. It must only use general purpose registers x1 and
x2 to do its work. The parameter and the return value are in general purpose
register x0.
diff --git a/drivers/arm/pl011/pl011_console.S b/drivers/arm/pl011/pl011_console.S
index 47608da..f29f895 100644
--- a/drivers/arm/pl011/pl011_console.S
+++ b/drivers/arm/pl011/pl011_console.S
@@ -54,7 +54,7 @@
* w1 - Uart clock in Hz
* w2 - Baud rate
* Out: return 1 on success else 0 on error
- * Clobber list : x1, x2
+ * Clobber list : x1, x2, x3, x4
* -----------------------------------------------
*/
func console_core_init
@@ -64,6 +64,20 @@
/* Check baud rate and uart clock for sanity */
cbz w1, core_init_fail
cbz w2, core_init_fail
+ /* Disable uart before programming */
+ ldr w3, [x0, #UARTCR]
+ mov w4, #PL011_UARTCR_UARTEN
+ bic w3, w3, w4
+ str w3, [x0, #UARTCR]
+ /* Flush the transmit FIFO */
+ ldr w3, [x0, #UARTLCR_H]
+ mov w4, #PL011_UARTLCR_H_FEN
+ bic w3, w3, w4
+ str w3, [x0, #UARTLCR_H]
+ /* Wait for the end of Tx of current character */
+busy_loop:
+ ldr w3, [x0, #UARTFR]
+ tbnz w3, #PL011_UARTFR_BUSY_BIT, busy_loop
/* Program the baudrate */
/* Divisor = (Uart clock * 4) / baudrate */
lsl w1, w1, #2
diff --git a/drivers/console/console.S b/drivers/console/console.S
index b772363..797b564 100644
--- a/drivers/console/console.S
+++ b/drivers/console/console.S
@@ -54,7 +54,7 @@
* w1 - Uart clock in Hz
* w2 - Baud rate
* out: return 1 on success else 0 on error
- * Clobber list : x1 - x3
+ * Clobber list : x1 - x4
* -----------------------------------------------
*/
func console_init
diff --git a/include/drivers/arm/pl011.h b/include/drivers/arm/pl011.h
index d5ea890..ce6cdcf 100644
--- a/include/drivers/arm/pl011.h
+++ b/include/drivers/arm/pl011.h
@@ -71,6 +71,7 @@
#define PL011_UARTFR_TXFF_BIT 5 /* Transmit FIFO full bit in UARTFR register */
#define PL011_UARTFR_RXFE_BIT 4 /* Receive FIFO empty bit in UARTFR register */
+#define PL011_UARTFR_BUSY_BIT 3 /* UART busy bit in UARTFR register */
/* Control reg bits */
#if !PL011_GENERIC_UART
diff --git a/plat/arm/common/aarch64/arm_helpers.S b/plat/arm/common/aarch64/arm_helpers.S
index 87179da..a0338f1 100644
--- a/plat/arm/common/aarch64/arm_helpers.S
+++ b/plat/arm/common/aarch64/arm_helpers.S
@@ -66,7 +66,7 @@
* int plat_crash_console_init(void)
* Function to initialize the crash console
* without a C Runtime to print crash report.
- * Clobber list : x0, x1, x2
+ * Clobber list : x0 - x4
* ---------------------------------------------
*/
func plat_crash_console_init
diff --git a/plat/mediatek/mt8173/aarch64/plat_helpers.S b/plat/mediatek/mt8173/aarch64/plat_helpers.S
index 99a054c..af3a407 100644
--- a/plat/mediatek/mt8173/aarch64/plat_helpers.S
+++ b/plat/mediatek/mt8173/aarch64/plat_helpers.S
@@ -63,7 +63,7 @@
* int plat_crash_console_init(void)
* Function to initialize the crash console
* without a C Runtime to print crash report.
- * Clobber list : x0, x1, x2
+ * Clobber list : x0 - x4
* ---------------------------------------------
*/
func plat_crash_console_init
diff --git a/plat/nvidia/tegra/common/aarch64/tegra_helpers.S b/plat/nvidia/tegra/common/aarch64/tegra_helpers.S
index a4caf5e..905c4c5 100644
--- a/plat/nvidia/tegra/common/aarch64/tegra_helpers.S
+++ b/plat/nvidia/tegra/common/aarch64/tegra_helpers.S
@@ -186,7 +186,7 @@
* int plat_crash_console_init(void)
* Function to initialize the crash console
* without a C Runtime to print crash report.
- * Clobber list : x0, x1, x2
+ * Clobber list : x0 - x4
* ---------------------------------------------
*/
func plat_crash_console_init