From 9400b40ea4c71153a63c1f1cdaa416d45a325ec5 Mon Sep 17 00:00:00 2001 From: Juan Castillo Date: Thu, 26 Nov 2015 14:52:15 +0000 Subject: 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 --- drivers/arm/pl011/pl011_console.S | 16 +++++++++++++++- drivers/console/console.S | 2 +- 2 files changed, 16 insertions(+), 2 deletions(-) (limited to 'drivers') diff --git a/drivers/arm/pl011/pl011_console.S b/drivers/arm/pl011/pl011_console.S index 47608da3..f29f895b 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 @@ func console_core_init /* 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 b7723638..797b5645 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 -- cgit