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From d25a404a959a57804908c1d615b2ac85d7c4a18e Mon Sep 17 00:00:00 2001
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From: Phil Elwell <phil@raspberrypi.org>
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Date: Wed, 1 Mar 2017 16:07:39 +0000
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Subject: [PATCH 093/454] amba_pl011: Round input clock up
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The UART clock is initialised to be as close to the requested
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frequency as possible without exceeding it. Now that there is a
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clock manager that returns the actual frequencies, an expected
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48MHz clock is reported as 47999625. If the requested baudrate
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== requested clock/16, there is no headroom and the slight
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reduction in actual clock rate results in failure.
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Detect cases where it looks like a "round" clock was chosen and
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adjust the reported clock to match that "round" value. As the
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code comment says:
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/*
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* If increasing a clock by less than 0.1% changes it
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* from ..999.. to ..000.., round up.
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*/
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Signed-off-by: Phil Elwell <phil@raspberrypi.org>
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---
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drivers/tty/serial/amba-pl011.c | 23 +++++++++++++++++++++--
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1 file changed, 21 insertions(+), 2 deletions(-)
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--- a/drivers/tty/serial/amba-pl011.c
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+++ b/drivers/tty/serial/amba-pl011.c
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@@ -1670,6 +1670,23 @@ static void pl011_put_poll_char(struct u
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#endif /* CONFIG_CONSOLE_POLL */
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+unsigned long pl011_clk_round(unsigned long clk)
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+{
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+ unsigned long scaler;
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+
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+ /*
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+ * If increasing a clock by less than 0.1% changes it
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+ * from ..999.. to ..000.., round up.
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+ */
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+ scaler = 1;
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+ while (scaler * 100000 < clk)
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+ scaler *= 10;
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+ if ((clk + scaler - 1)/scaler % 1000 == 0)
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+ clk = (clk/scaler + 1) * scaler;
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+
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+ return clk;
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+}
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+
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static int pl011_hwinit(struct uart_port *port)
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{
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struct uart_amba_port *uap =
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@@ -1686,7 +1703,7 @@ static int pl011_hwinit(struct uart_port
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if (retval)
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return retval;
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- uap->port.uartclk = clk_get_rate(uap->clk);
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+ uap->port.uartclk = pl011_clk_round(clk_get_rate(uap->clk));
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/* Clear pending error and receive interrupts */
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pl011_write(UART011_OEIS | UART011_BEIS | UART011_PEIS |
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@@ -2342,7 +2359,7 @@ static int __init pl011_console_setup(st
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plat->init();
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}
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- uap->port.uartclk = clk_get_rate(uap->clk);
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+ uap->port.uartclk = pl011_clk_round(clk_get_rate(uap->clk));
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if (uap->vendor->fixed_options) {
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baud = uap->fixed_baud;
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@@ -2527,6 +2544,7 @@ static struct uart_driver amba_reg = {
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.cons = AMBA_CONSOLE,
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};
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+#if 0
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static int pl011_probe_dt_alias(int index, struct device *dev)
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{
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struct device_node *np;
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@@ -2558,6 +2576,7 @@ static int pl011_probe_dt_alias(int inde
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return ret;
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}
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+#endif
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/* unregisters the driver also if no more ports are left */
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static void pl011_unregister_port(struct uart_amba_port *uap)
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