[Xen-devel] [PATCH V9 1/3] drivers/pl011: Don't configure baudrate

[Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxx>
Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
---
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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