[PATCH AUTOSEL 4.4 03/35] tty: max310x: Fix invalid baudrate divisors calculator

[PATCH AUTOSEL 4.4 03/35] tty: max310x: Fix invalid baudrate divisors calculator

[Sasha Levin]

From: Serge Semin <fancer.lancer@gmail.com>

[ Upstream commit 35240ba26a932b279a513f66fa4cabfd7af55221 ]

Current calculator doesn't do it' job quite correct. First of all the
max310x baud-rates generator supports the divisor being less than 16.
In this case the x2/x4 modes can be used to double or quadruple
the reference frequency. But the current baud-rate setter function
just filters all these modes out by the first condition and setups
these modes only if there is a clocks-baud division remainder. The former
doesn't seem right at all, since enabling the x2/x4 modes causes the line
noise tolerance reduction and should be only used as a last resort to
enable a requested too high baud-rate.

Finally the fraction is supposed to be calculated from D = Fref/(c*baud)
formulae, but not from D % 16, which causes the precision loss. So to speak
the current baud-rate calculator code works well only if the baud perfectly
fits to the uart reference input frequency.

Lets fix the calculator by implementing the algo fully compliant with
the fractional baud-rate generator described in the datasheet:
D = Fref / (c*baud), where c={16,8,4} is the x1/x2/x4 rate mode
respectively, Fref - reference input frequency. The divisor fraction is
calculated from the same formulae, but making sure it is found with a
resolution of 0.0625 (four bits).

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/max310x.c | 51 ++++++++++++++++++++++--------------
 1 file changed, 31 insertions(+), 20 deletions(-)

diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index 0ac0c618954e..a66fb7afecc7 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -486,37 +486,48 @@ static bool max310x_reg_precious(struct device *dev, unsigned int reg)
 
 static int max310x_set_baud(struct uart_port *port, int baud)
 {
-	unsigned int mode = 0, clk = port->uartclk, div = clk / baud;
+	unsigned int mode = 0, div = 0, frac = 0, c = 0, F = 0;
 
-	/* Check for minimal value for divider */
-	if (div < 16)
-		div = 16;
-
-	if (clk % baud && (div / 16) < 0x8000) {
+	/*
+	 * Calculate the integer divisor first. Select a proper mode
+	 * in case if the requested baud is too high for the pre-defined
+	 * clocks frequency.
+	 */
+	div = port->uartclk / baud;
+	if (div < 8) {
+		/* Mode x4 */
+		c = 4;
+		mode = MAX310X_BRGCFG_4XMODE_BIT;
+	} else if (div < 16) {
 		/* Mode x2 */
+		c = 8;
 		mode = MAX310X_BRGCFG_2XMODE_BIT;
-		clk = port->uartclk * 2;
-		div = clk / baud;
-
-		if (clk % baud && (div / 16) < 0x8000) {
-			/* Mode x4 */
-			mode = MAX310X_BRGCFG_4XMODE_BIT;
-			clk = port->uartclk * 4;
-			div = clk / baud;
-		}
+	} else {
+		c = 16;
 	}
 
-	max310x_port_write(port, MAX310X_BRGDIVMSB_REG, (div / 16) >> 8);
-	max310x_port_write(port, MAX310X_BRGDIVLSB_REG, div / 16);
-	max310x_port_write(port, MAX310X_BRGCFG_REG, (div % 16) | mode);
+	/* Calculate the divisor in accordance with the fraction coefficient */
+	div /= c;
+	F = c*baud;
+
+	/* Calculate the baud rate fraction */
+	if (div > 0)
+		frac = (16*(port->uartclk % F)) / F;
+	else
+		div = 1;
+
+	max310x_port_write(port, MAX310X_BRGDIVMSB_REG, div >> 8);
+	max310x_port_write(port, MAX310X_BRGDIVLSB_REG, div);
+	max310x_port_write(port, MAX310X_BRGCFG_REG, frac | mode);
 
-	return DIV_ROUND_CLOSEST(clk, div);
+	/* Return the actual baud rate we just programmed */
+	return (16*port->uartclk) / (c*(16*div + frac));
 }
 
 static int max310x_update_best_err(unsigned long f, long *besterr)
 {
 	/* Use baudrate 115200 for calculate error */
-	long err = f % (115200 * 16);
+	long err = f % (460800 * 16);
 
 	if ((*besterr < 0) || (*besterr > err)) {
 		*besterr = err;
-- 
2.20.1

[PATCH AUTOSEL 4.4 05/35] tty: serial: cpm_uart - fix init when SMC is relocated

[Sasha Levin]

From: Christophe Leroy <christophe.leroy@c-s.fr>

[ Upstream commit 06aaa3d066db87e8478522d910285141d44b1e58 ]

SMC relocation can also be activated earlier by the bootloader,
so the driver's behaviour cannot rely on selected kernel config.

When the SMC is relocated, CPM_CR_INIT_TRX cannot be used.

But the only thing CPM_CR_INIT_TRX does is to clear the
rstate and tstate registers, so this can be done manually,
even when SMC is not relocated.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Fixes: 9ab921201444 ("cpm_uart: fix non-console port startup bug")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/cpm_uart/cpm_uart_core.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/cpm_uart/cpm_uart_core.c b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
index 0040c29f651a..b9e137c03fe3 100644
--- a/drivers/tty/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
@@ -421,7 +421,16 @@ static int cpm_uart_startup(struct uart_port *port)
 			clrbits16(&pinfo->sccp->scc_sccm, UART_SCCM_RX);
 		}
 		cpm_uart_initbd(pinfo);
-		cpm_line_cr_cmd(pinfo, CPM_CR_INIT_TRX);
+		if (IS_SMC(pinfo)) {
+			out_be32(&pinfo->smcup->smc_rstate, 0);
+			out_be32(&pinfo->smcup->smc_tstate, 0);
+			out_be16(&pinfo->smcup->smc_rbptr,
+				 in_be16(&pinfo->smcup->smc_rbase));
+			out_be16(&pinfo->smcup->smc_tbptr,
+				 in_be16(&pinfo->smcup->smc_tbase));
+		} else {
+			cpm_line_cr_cmd(pinfo, CPM_CR_INIT_TRX);
+		}
 	}
 	/* Install interrupt handler. */
 	retval = request_irq(port->irq, cpm_uart_int, 0, "cpm_uart", port);
@@ -875,16 +884,14 @@ static void cpm_uart_init_smc(struct uart_cpm_port *pinfo)
 	         (u8 __iomem *)pinfo->tx_bd_base - DPRAM_BASE);
 
 /*
- *  In case SMC1 is being relocated...
+ *  In case SMC is being relocated...
  */
-#if defined (CONFIG_I2C_SPI_SMC1_UCODE_PATCH)
 	out_be16(&up->smc_rbptr, in_be16(&pinfo->smcup->smc_rbase));
 	out_be16(&up->smc_tbptr, in_be16(&pinfo->smcup->smc_tbase));
 	out_be32(&up->smc_rstate, 0);
 	out_be32(&up->smc_tstate, 0);
 	out_be16(&up->smc_brkcr, 1);              /* number of break chars */
 	out_be16(&up->smc_brkec, 0);
-#endif
 
 	/* Set up the uart parameters in the
 	 * parameter ram.
@@ -898,8 +905,6 @@ static void cpm_uart_init_smc(struct uart_cpm_port *pinfo)
 	out_be16(&up->smc_brkec, 0);
 	out_be16(&up->smc_brkcr, 1);
 
-	cpm_line_cr_cmd(pinfo, CPM_CR_INIT_TRX);
-
 	/* Set UART mode, 8 bit, no parity, one stop.
 	 * Enable receive and transmit.
 	 */
-- 
2.20.1

[PATCH AUTOSEL 4.4 08/35] tty/serial: digicolor: Fix digicolor-usart already registered warning

[Sasha Levin]

From: Kefeng Wang <wangkefeng.wang@huawei.com>

[ Upstream commit c7ad9ba0611c53cfe194223db02e3bca015f0674 ]

When modprobe/rmmod/modprobe module, if platform_driver_register() fails,
the kernel complained,

  proc_dir_entry 'driver/digicolor-usart' already registered
  WARNING: CPU: 1 PID: 5636 at fs/proc/generic.c:360 proc_register+0x19d/0x270

Fix this by adding uart_unregister_driver() when platform_driver_register() fails.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/digicolor-usart.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/digicolor-usart.c b/drivers/tty/serial/digicolor-usart.c
index a80cdad114f3..d8cb94997487 100644
--- a/drivers/tty/serial/digicolor-usart.c
+++ b/drivers/tty/serial/digicolor-usart.c
@@ -544,7 +544,11 @@ static int __init digicolor_uart_init(void)
 	if (ret)
 		return ret;
 
-	return platform_driver_register(&digicolor_uart_platform);
+	ret = platform_driver_register(&digicolor_uart_platform);
+	if (ret)
+		uart_unregister_driver(&digicolor_uart);
+
+	return ret;
 }
 module_init(digicolor_uart_init);
 
-- 
2.20.1

[PATCH AUTOSEL 4.4 09/35] tty: serial: msm_serial: avoid system lockup condition

[Sasha Levin]

From: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>

[ Upstream commit ba3684f99f1b25d2a30b6956d02d339d7acb9799 ]

The function msm_wait_for_xmitr can be taken with interrupts
disabled. In order to avoid a potential system lockup - demonstrated
under stress testing conditions on SoC QCS404/5 - make sure we wait
for a bounded amount of time.

Tested on SoC QCS404.

Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/msm_serial.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 5f0ded6fc4e9..eaeb098b5d6a 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -222,10 +222,14 @@ static void msm_request_rx_dma(struct msm_port *msm_port, resource_size_t base)
 
 static inline void msm_wait_for_xmitr(struct uart_port *port)
 {
+	unsigned int timeout = 500000;
+
 	while (!(msm_read(port, UART_SR) & UART_SR_TX_EMPTY)) {
 		if (msm_read(port, UART_ISR) & UART_ISR_TX_READY)
 			break;
 		udelay(1);
+		if (!timeout--)
+			break;
 	}
 	msm_write(port, UART_CR_CMD_RESET_TX_READY, UART_CR);
 }
-- 
2.20.1

[PATCH AUTOSEL 4.4 24/35] serial: sh-sci: Fix TX DMA buffer flushing and workqueue races

[Sasha Levin]

From: Geert Uytterhoeven <geert+renesas@glider.be>

[ Upstream commit 8493eab02608b0e82f67b892aa72882e510c31d0 ]

When uart_flush_buffer() is called, the .flush_buffer() callback zeroes
the tx_dma_len field.  This may race with the work queue function
handling transmit DMA requests:

  1. If the buffer is flushed before the first DMA API call,
     dmaengine_prep_slave_single() may be called with a zero length,
     causing the DMA request to never complete, leading to messages
     like:

        rcar-dmac e7300000.dma-controller: Channel Address Error happen

     and, with debug enabled:

	sh-sci e6e88000.serial: sci_dma_tx_work_fn: ffff800639b55000: 0...0, cookie 126

     and DMA timeouts.

  2. If the buffer is flushed after the first DMA API call, but before
     the second, dma_sync_single_for_device() may be called with a zero
     length, causing the transmit data not to be flushed to RAM, and
     leading to stale data being output.

Fix this by:
  1. Letting sci_dma_tx_work_fn() return immediately if the transmit
     buffer is empty,
  2. Extending the critical section to cover all DMA preparational work,
     so tx_dma_len stays consistent for all of it,
  3. Using local copies of circ_buf.head and circ_buf.tail, to make sure
     they match the actual operation above.

Reported-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Suggested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Link: https://lore.kernel.org/r/20190624123540.20629-2-geert+renesas@glider.be
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/sh-sci.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 669134e27ed9..c450e32c153d 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1203,6 +1203,7 @@ static void work_fn_tx(struct work_struct *work)
 	struct uart_port *port = &s->port;
 	struct circ_buf *xmit = &port->state->xmit;
 	dma_addr_t buf;
+	int head, tail;
 
 	/*
 	 * DMA is idle now.
@@ -1212,16 +1213,23 @@ static void work_fn_tx(struct work_struct *work)
 	 * consistent xmit buffer state.
 	 */
 	spin_lock_irq(&port->lock);
-	buf = s->tx_dma_addr + (xmit->tail & (UART_XMIT_SIZE - 1));
+	head = xmit->head;
+	tail = xmit->tail;
+	buf = s->tx_dma_addr + (tail & (UART_XMIT_SIZE - 1));
 	s->tx_dma_len = min_t(unsigned int,
-		CIRC_CNT(xmit->head, xmit->tail, UART_XMIT_SIZE),
-		CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE));
-	spin_unlock_irq(&port->lock);
+		CIRC_CNT(head, tail, UART_XMIT_SIZE),
+		CIRC_CNT_TO_END(head, tail, UART_XMIT_SIZE));
+	if (!s->tx_dma_len) {
+		/* Transmit buffer has been flushed */
+		spin_unlock_irq(&port->lock);
+		return;
+	}
 
 	desc = dmaengine_prep_slave_single(chan, buf, s->tx_dma_len,
 					   DMA_MEM_TO_DEV,
 					   DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 	if (!desc) {
+		spin_unlock_irq(&port->lock);
 		dev_warn(port->dev, "Failed preparing Tx DMA descriptor\n");
 		/* switch to PIO */
 		sci_tx_dma_release(s, true);
@@ -1231,20 +1239,20 @@ static void work_fn_tx(struct work_struct *work)
 	dma_sync_single_for_device(chan->device->dev, buf, s->tx_dma_len,
 				   DMA_TO_DEVICE);
 
-	spin_lock_irq(&port->lock);
 	desc->callback = sci_dma_tx_complete;
 	desc->callback_param = s;
-	spin_unlock_irq(&port->lock);
 	s->cookie_tx = dmaengine_submit(desc);
 	if (dma_submit_error(s->cookie_tx)) {
+		spin_unlock_irq(&port->lock);
 		dev_warn(port->dev, "Failed submitting Tx DMA descriptor\n");
 		/* switch to PIO */
 		sci_tx_dma_release(s, true);
 		return;
 	}
 
+	spin_unlock_irq(&port->lock);
 	dev_dbg(port->dev, "%s: %p: %d...%d, cookie %d\n",
-		__func__, xmit->buf, xmit->tail, xmit->head, s->cookie_tx);
+		__func__, xmit->buf, tail, head, s->cookie_tx);
 
 	dma_async_issue_pending(chan);
 }
-- 
2.20.1