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From: Shanker Donthineni <shankerd@codeaurora.org>
To: xen-devel <xen-devel@lists.xensource.com>,
	Julien Grall <julien.grall@arm.com>,
	Stefano Stabellini <sstabellini@kernel.org>
Cc: Andre Przywara <andre.przywara@arm.com>,
	Philip Elcan <pelcan@codeaurora.org>,
	Shanker Donthineni <shankerd@codeaurora.org>,
	Vikram Sethi <vikrams@codeaurora.org>,
	Wei Chen <wei.chen@linaro.org>
Subject: [PATCH V7 1/3] drivers/pl011: Don't configure baudrate
Date: Tue,  7 Jun 2016 14:04:02 -0500	[thread overview]
Message-ID: <1465326244-10802-1-git-send-email-shankerd@codeaurora.org> (raw)

The default baud and clock_hz configuration parameters are hardcoded
(commit 60ff9444480995008caf) for Versatile Express. Other platforms,
these default values may not be valid and might cause problems by
programming registers IBRD and FBRD incorrectly.

So, removing driver logic that sets the baudrate to fix the problem.
The behavior is unchanged because the driver was already relying on
the boot firmware for setting the correct baudrate.

Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Reviewed-by: Julien Grall <julien.grall@arm.com>
---
Changes since v1:
  Edited commit text.

 xen/drivers/char/pl011.c | 21 +--------------------
 1 file changed, 1 insertion(+), 20 deletions(-)

diff --git a/xen/drivers/char/pl011.c b/xen/drivers/char/pl011.c
index 1212d5c..6a3c21b 100644
--- a/xen/drivers/char/pl011.c
+++ b/xen/drivers/char/pl011.c
@@ -31,7 +31,7 @@
 #include <asm/io.h>
 
 static struct pl011 {
-    unsigned int baud, clock_hz, data_bits, parity, stop_bits;
+    unsigned int data_bits, parity, stop_bits;
     unsigned int irq;
     void __iomem *regs;
     /* UART with IRQ line: interrupt-driven I/O. */
@@ -84,7 +84,6 @@ static void pl011_interrupt(int irq, void *data, struct cpu_user_regs *regs)
 static void __init pl011_init_preirq(struct serial_port *port)
 {
     struct pl011 *uart = port->uart;
-    unsigned int divisor;
     unsigned int cr;
 
     /* No interrupts, please. */
@@ -93,22 +92,6 @@ static void __init pl011_init_preirq(struct serial_port *port)
     /* Definitely no DMA */
     pl011_write(uart, DMACR, 0x0);
 
-    /* Line control and baud-rate generator. */
-    if ( uart->baud != BAUD_AUTO )
-    {
-        /* Baud rate specified: program it into the divisor latch. */
-        divisor = (uart->clock_hz << 2) / uart->baud; /* clk << 6 / bd << 4 */
-        pl011_write(uart, FBRD, divisor & 0x3f);
-        pl011_write(uart, IBRD, divisor >> 6);
-    }
-    else
-    {
-        /* Baud rate already set: read it out from the divisor latch. */
-        divisor = (pl011_read(uart, IBRD) << 6) | (pl011_read(uart, FBRD));
-        if (!divisor)
-            panic("pl011: No Baud rate configured\n");
-        uart->baud = (uart->clock_hz << 2) / divisor;
-    }
     /* This write must follow FBRD and IBRD writes. */
     pl011_write(uart, LCR_H, (uart->data_bits - 5) << 5
                             | FEN
@@ -232,8 +215,6 @@ static int __init pl011_uart_init(int irq, u64 addr, u64 size)
 
     uart = &pl011_com;
     uart->irq       = irq;
-    uart->clock_hz  = 0x16e3600;
-    uart->baud      = BAUD_AUTO;
     uart->data_bits = 8;
     uart->parity    = PARITY_NONE;
     uart->stop_bits = 1;
-- 
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc. 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, 
a Linux Foundation Collaborative Project


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             reply	other threads:[~2016-06-07 19:04 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-07 19:04 Shanker Donthineni [this message]
2016-06-07 19:04 ` [PATCH V7 2/3] drivers/pl011: Use combination of UARTRIS and UARTMSC instead of UARTMIS Shanker Donthineni
2016-06-08  9:06   ` Julien Grall
2016-06-07 19:04 ` [PATCH V7 3/3] arm/acpi: Add Server Base System Architecture UART support Shanker Donthineni

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