amba pl011: workaround for uart registers lockup
This workaround aims to break the deadlock situation
which raises during continuous transfer of data for long
duration over uart with hardware flow control. It is
observed that CTS interrupt cannot be cleared in uart
interrupt register (ICR). Hence further transfer over
uart gets blocked.
It is seen that during such deadlock condition ICR
don't get cleared even on multiple write. This leads
pass_counter to decrease and finally reach zero. This
can be taken as trigger point to run this UART_BT_WA.
Workaround backups the register configuration, does soft
reset of UART using BIT-0 of PRCC_K_SOFTRST_SET/CLEAR
registers and restores the registers.
This patch also provides support for uart init and exit
function calls if present.
Signed-off-by: Shreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 8dc0541..f5f6831 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -50,6 +50,7 @@
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/scatterlist.h>
+#include <linux/delay.h>
#include <asm/io.h>
#include <asm/sizes.h>
@@ -65,6 +66,30 @@
#define UART_DR_ERROR (UART011_DR_OE|UART011_DR_BE|UART011_DR_PE|UART011_DR_FE)
#define UART_DUMMY_DR_RX (1 << 16)
+
+#define UART_WA_SAVE_NR 14
+
+static void pl011_lockup_wa(unsigned long data);
+static const u32 uart_wa_reg[UART_WA_SAVE_NR] = {
+ ST_UART011_DMAWM,
+ ST_UART011_TIMEOUT,
+ ST_UART011_LCRH_RX,
+ UART011_IBRD,
+ UART011_FBRD,
+ ST_UART011_LCRH_TX,
+ UART011_IFLS,
+ ST_UART011_XFCR,
+ ST_UART011_XON1,
+ ST_UART011_XON2,
+ ST_UART011_XOFF1,
+ ST_UART011_XOFF2,
+ UART011_CR,
+ UART011_IMSC
+};
+
+static u32 uart_wa_regdata[UART_WA_SAVE_NR];
+static DECLARE_TASKLET(pl011_lockup_tlet, pl011_lockup_wa, 0);
+
/* There is by now at least one vendor with differing details, so handle it */
struct vendor_data {
unsigned int ifls;
@@ -72,6 +97,7 @@
unsigned int lcrh_tx;
unsigned int lcrh_rx;
bool oversampling;
+ bool interrupt_may_hang; /* vendor-specific */
bool dma_threshold;
};
@@ -90,9 +116,12 @@
.lcrh_tx = ST_UART011_LCRH_TX,
.lcrh_rx = ST_UART011_LCRH_RX,
.oversampling = true,
+ .interrupt_may_hang = true,
.dma_threshold = true,
};
+static struct uart_amba_port *amba_ports[UART_NR];
+
/* Deals with DMA transactions */
struct pl011_sgbuf {
@@ -132,6 +161,7 @@
unsigned int lcrh_rx; /* vendor-specific */
bool autorts;
char type[12];
+ bool interrupt_may_hang; /* vendor-specific */
#ifdef CONFIG_DMA_ENGINE
/* DMA stuff */
bool using_tx_dma;
@@ -1008,6 +1038,68 @@
#endif
+/*
+ * pl011_lockup_wa
+ * This workaround aims to break the deadlock situation
+ * when after long transfer over uart in hardware flow
+ * control, uart interrupt registers cannot be cleared.
+ * Hence uart transfer gets blocked.
+ *
+ * It is seen that during such deadlock condition ICR
+ * don't get cleared even on multiple write. This leads
+ * pass_counter to decrease and finally reach zero. This
+ * can be taken as trigger point to run this UART_BT_WA.
+ *
+ */
+static void pl011_lockup_wa(unsigned long data)
+{
+ struct uart_amba_port *uap = amba_ports[0];
+ void __iomem *base = uap->port.membase;
+ struct circ_buf *xmit = &uap->port.state->xmit;
+ struct tty_struct *tty = uap->port.state->port.tty;
+ int buf_empty_retries = 200;
+ int loop;
+
+ /* Stop HCI layer from submitting data for tx */
+ tty->hw_stopped = 1;
+ while (!uart_circ_empty(xmit)) {
+ if (buf_empty_retries-- == 0)
+ break;
+ udelay(100);
+ }
+
+ /* Backup registers */
+ for (loop = 0; loop < UART_WA_SAVE_NR; loop++)
+ uart_wa_regdata[loop] = readl(base + uart_wa_reg[loop]);
+
+ /* Disable UART so that FIFO data is flushed out */
+ writew(0x00, uap->port.membase + UART011_CR);
+
+ /* Soft reset UART module */
+ if (uap->port.dev->platform_data) {
+ struct amba_pl011_data *plat;
+
+ plat = uap->port.dev->platform_data;
+ if (plat->reset)
+ plat->reset();
+ }
+
+ /* Restore registers */
+ for (loop = 0; loop < UART_WA_SAVE_NR; loop++)
+ writew(uart_wa_regdata[loop] ,
+ uap->port.membase + uart_wa_reg[loop]);
+
+ /* Initialise the old status of the modem signals */
+ uap->old_status = readw(uap->port.membase + UART01x_FR) &
+ UART01x_FR_MODEM_ANY;
+
+ if (readl(base + UART011_MIS) & 0x2)
+ printk(KERN_EMERG "UART_BT_WA: ***FAILED***\n");
+
+ /* Start Tx/Rx */
+ tty->hw_stopped = 0;
+}
+
static void pl011_stop_tx(struct uart_port *port)
{
struct uart_amba_port *uap = (struct uart_amba_port *)port;
@@ -1158,8 +1250,11 @@
if (status & UART011_TXIS)
pl011_tx_chars(uap);
- if (pass_counter-- == 0)
+ if (pass_counter-- == 0) {
+ if (uap->interrupt_may_hang)
+ tasklet_schedule(&pl011_lockup_tlet);
break;
+ }
status = readw(uap->port.membase + UART011_MIS);
} while (status != 0);
@@ -1339,6 +1434,14 @@
writew(uap->im, uap->port.membase + UART011_IMSC);
spin_unlock_irq(&uap->port.lock);
+ if (uap->port.dev->platform_data) {
+ struct amba_pl011_data *plat;
+
+ plat = uap->port.dev->platform_data;
+ if (plat->init)
+ plat->init();
+ }
+
return 0;
clk_dis:
@@ -1394,6 +1497,15 @@
* Shut down the clock producer
*/
clk_disable(uap->clk);
+
+ if (uap->port.dev->platform_data) {
+ struct amba_pl011_data *plat;
+
+ plat = uap->port.dev->platform_data;
+ if (plat->exit)
+ plat->exit();
+ }
+
}
static void
@@ -1700,6 +1812,14 @@
if (!uap)
return -ENODEV;
+ if (uap->port.dev->platform_data) {
+ struct amba_pl011_data *plat;
+
+ plat = uap->port.dev->platform_data;
+ if (plat->init)
+ plat->init();
+ }
+
uap->port.uartclk = clk_get_rate(uap->clk);
if (options)
@@ -1774,6 +1894,7 @@
uap->lcrh_rx = vendor->lcrh_rx;
uap->lcrh_tx = vendor->lcrh_tx;
uap->fifosize = vendor->fifosize;
+ uap->interrupt_may_hang = vendor->interrupt_may_hang;
uap->port.dev = &dev->dev;
uap->port.mapbase = dev->res.start;
uap->port.membase = base;