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https://github.com/AsahiLinux/u-boot
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601147b06a
On the raspberry pi, you can disable the serial port to gain dynamic frequency scaling which can get handy at times. However, in such a configuration the serial controller gets its rx queue filled up with zero bytes which then happily get transmitted on to whoever calls getc() today. This patch adds detection logic for that case by checking whether the RX pin is mapped to GPIO15 and disables the mini uart if it is not mapped properly. That way we can leave the driver enabled in the tree and can determine during runtime whether serial is usable or not, having a single binary that allows for uart and non-uart operation. Signed-off-by: Alexander Graf <agraf@suse.de> Acked-by: Stephen Warren <swarren@wwwdotorg.org> Reviewed-by: Simon Glass <sjg@chromium.org>
143 lines
3.2 KiB
C
143 lines
3.2 KiB
C
/*
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* (C) Copyright 2016 Stephen Warren <swarren@wwwdotorg.org>
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*
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* Derived from pl01x code:
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*
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* (C) Copyright 2000
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* Rob Taylor, Flying Pig Systems. robt@flyingpig.com.
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*
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* (C) Copyright 2004
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* ARM Ltd.
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* Philippe Robin, <philippe.robin@arm.com>
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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/* Simple U-Boot driver for the BCM283x mini UART */
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#include <common.h>
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#include <dm.h>
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#include <errno.h>
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#include <watchdog.h>
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#include <asm/io.h>
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#include <serial.h>
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#include <dm/platform_data/serial_bcm283x_mu.h>
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#include <linux/compiler.h>
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#include <fdtdec.h>
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struct bcm283x_mu_regs {
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u32 io;
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u32 iir;
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u32 ier;
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u32 lcr;
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u32 mcr;
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u32 lsr;
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u32 msr;
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u32 scratch;
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u32 cntl;
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u32 stat;
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u32 baud;
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};
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#define BCM283X_MU_LCR_DATA_SIZE_8 3
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#define BCM283X_MU_LSR_TX_IDLE BIT(6)
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/* This actually means not full, but is named not empty in the docs */
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#define BCM283X_MU_LSR_TX_EMPTY BIT(5)
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#define BCM283X_MU_LSR_RX_READY BIT(0)
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struct bcm283x_mu_priv {
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struct bcm283x_mu_regs *regs;
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};
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static int bcm283x_mu_serial_setbrg(struct udevice *dev, int baudrate)
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{
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struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
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struct bcm283x_mu_priv *priv = dev_get_priv(dev);
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struct bcm283x_mu_regs *regs = priv->regs;
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u32 divider;
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if (plat->skip_init)
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return 0;
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divider = plat->clock / (baudrate * 8);
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writel(BCM283X_MU_LCR_DATA_SIZE_8, ®s->lcr);
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writel(divider - 1, ®s->baud);
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return 0;
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}
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static int bcm283x_mu_serial_probe(struct udevice *dev)
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{
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struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
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struct bcm283x_mu_priv *priv = dev_get_priv(dev);
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if (plat->disabled)
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return -ENODEV;
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priv->regs = (struct bcm283x_mu_regs *)plat->base;
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return 0;
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}
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static int bcm283x_mu_serial_getc(struct udevice *dev)
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{
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struct bcm283x_mu_priv *priv = dev_get_priv(dev);
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struct bcm283x_mu_regs *regs = priv->regs;
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u32 data;
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/* Wait until there is data in the FIFO */
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if (!(readl(®s->lsr) & BCM283X_MU_LSR_RX_READY))
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return -EAGAIN;
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data = readl(®s->io);
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return (int)data;
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}
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static int bcm283x_mu_serial_putc(struct udevice *dev, const char data)
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{
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struct bcm283x_mu_priv *priv = dev_get_priv(dev);
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struct bcm283x_mu_regs *regs = priv->regs;
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/* Wait until there is space in the FIFO */
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if (!(readl(®s->lsr) & BCM283X_MU_LSR_TX_EMPTY))
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return -EAGAIN;
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/* Send the character */
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writel(data, ®s->io);
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return 0;
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}
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static int bcm283x_mu_serial_pending(struct udevice *dev, bool input)
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{
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struct bcm283x_mu_priv *priv = dev_get_priv(dev);
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struct bcm283x_mu_regs *regs = priv->regs;
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unsigned int lsr = readl(®s->lsr);
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if (input) {
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WATCHDOG_RESET();
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return (lsr & BCM283X_MU_LSR_RX_READY) ? 1 : 0;
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} else {
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return (lsr & BCM283X_MU_LSR_TX_IDLE) ? 0 : 1;
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}
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}
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static const struct dm_serial_ops bcm283x_mu_serial_ops = {
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.putc = bcm283x_mu_serial_putc,
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.pending = bcm283x_mu_serial_pending,
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.getc = bcm283x_mu_serial_getc,
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.setbrg = bcm283x_mu_serial_setbrg,
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};
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U_BOOT_DRIVER(serial_bcm283x_mu) = {
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.name = "serial_bcm283x_mu",
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.id = UCLASS_SERIAL,
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.platdata_auto_alloc_size = sizeof(struct bcm283x_mu_serial_platdata),
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.probe = bcm283x_mu_serial_probe,
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.ops = &bcm283x_mu_serial_ops,
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.flags = DM_FLAG_PRE_RELOC,
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.priv_auto_alloc_size = sizeof(struct bcm283x_mu_priv),
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};
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