[PATCH v3] arm/acpi: Add Server Base System Architecture UART support

[Shanker Donthineni <shankerd@codeaurora.org>]

The ARM Server Base System Architecture describes a generic UART
interface. It doesn't support clock control registers, modem
control, DMA and hardware flow control features. So, extend the
driver probe() to handle SBSA interface and skip the accessing
PL011 registers that are not described in SBSA document
(ARM-DEN-0029 Version 3.0, 6 APPENDIX B: GENERIC UART).

Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
---
Changes since v2:
   Edited commit text to include SBSA document version.
   Remove setting baudrate code completely as per Julien's suggestion.
   Support both the SBSA interface types ACPI_DBG2_SBSA & ACPI_DBG2_SBSA_32.
   Replace MIS references with combination of RIS & IMSC.

Changes since v1:
   Don't access UART registers that are not part of SBSA document.
   Move setting baudrate function to a separate function.

 xen/drivers/char/pl011.c | 76 ++++++++++++++++++++++++++----------------------
 1 file changed, 41 insertions(+), 35 deletions(-)

diff --git a/xen/drivers/char/pl011.c b/xen/drivers/char/pl011.c
index 1212d5c..3497d61 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. */
@@ -41,6 +41,7 @@ static struct pl011 {
     /* struct timer timer; */
     /* unsigned int timeout_ms; */
     /* bool_t probing, intr_works; */
+    bool sbsa;  /* ARM SBSA generic interface */
 } pl011_com = {0};
 
 /* These parity settings can be ORed directly into the LCR. */
@@ -57,7 +58,9 @@ static void pl011_interrupt(int irq, void *data, struct cpu_user_regs *regs)
 {
     struct serial_port *port = data;
     struct pl011 *uart = port->uart;
-    unsigned int status = pl011_read(uart, MIS);
+    unsigned int status = pl011_read(uart, RIS);
+
+    status &= pl011_read(uart, IMSC);
 
     if ( status )
     {
@@ -76,7 +79,7 @@ static void pl011_interrupt(int irq, void *data, struct cpu_user_regs *regs)
             if ( status & (TXI) )
                 serial_tx_interrupt(port, regs);
 
-            status = pl011_read(uart, MIS);
+            status = pl011_read(uart, RIS) & pl011_read(uart, IMSC);
         } while (status != 0);
     }
 }
@@ -84,36 +87,22 @@ 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. */
     pl011_write(uart, IMSC, 0);
 
-    /* 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
+    if ( !uart->sbsa )
     {
-        /* 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;
+        /* Definitely no DMA */
+        pl011_write(uart, DMACR, 0x0);
+
+        /* This write must follow FBRD and IBRD writes. */
+        pl011_write(uart, LCR_H, (uart->data_bits - 5) << 5
+                                | FEN
+                                | ((uart->stop_bits - 1) << 3)
+                                | uart->parity);
     }
-    /* This write must follow FBRD and IBRD writes. */
-    pl011_write(uart, LCR_H, (uart->data_bits - 5) << 5
-                            | FEN
-                            | ((uart->stop_bits - 1) << 3)
-                            | uart->parity);
     /* Clear errors */
     pl011_write(uart, RSR, 0);
 
@@ -121,10 +110,13 @@ static void __init pl011_init_preirq(struct serial_port *port)
     pl011_write(uart, IMSC, 0);
     pl011_write(uart, ICR, ALLI);
 
-    /* Enable the UART for RX and TX; keep RTS and DTR */
-    cr = pl011_read(uart, CR);
-    cr &= RTS | DTR;
-    pl011_write(uart, CR, cr | RXE | TXE | UARTEN);
+    if ( !uart->sbsa )
+    {
+        /* Enable the UART for RX and TX; keep RTS and DTR */
+        cr = pl011_read(uart, CR);
+        cr &= RTS | DTR;
+        pl011_write(uart, CR, cr | RXE | TXE | UARTEN);
+    }
 }
 
 static void __init pl011_init_postirq(struct serial_port *port)
@@ -226,17 +218,16 @@ static struct uart_driver __read_mostly pl011_driver = {
     .vuart_info   = pl011_vuart,
 };
 
-static int __init pl011_uart_init(int irq, u64 addr, u64 size)
+static int __init pl011_uart_init(int irq, u64 addr, u64 size, bool sbsa)
 {
     struct pl011 *uart;
 
     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;
+    uart->sbsa = sbsa;
 
     uart->regs = ioremap_nocache(addr, size);
     if ( !uart->regs )
@@ -285,7 +276,7 @@ static int __init pl011_dt_uart_init(struct dt_device_node *dev,
         return -EINVAL;
     }
 
-    res = pl011_uart_init(res, addr, size);
+    res = pl011_uart_init(res, addr, size, false);
     if ( res < 0 )
     {
         printk("pl011: Unable to initialize\n");
@@ -315,6 +306,7 @@ static int __init pl011_acpi_uart_init(const void *data)
 {
     acpi_status status;
     struct acpi_table_spcr *spcr = NULL;
+    bool sbsa = false;
     int res;
 
     status = acpi_get_table(ACPI_SIG_SPCR, 0,
@@ -326,11 +318,15 @@ static int __init pl011_acpi_uart_init(const void *data)
         return -EINVAL;
     }
 
+    if ( (spcr->interface_type == ACPI_DBG2_SBSA) ||
+         (spcr->interface_type == ACPI_DBG2_SBSA_32) )
+        sbsa = true;
+
     /* trigger/polarity information is not available in spcr */
     irq_set_type(spcr->interrupt, IRQ_TYPE_LEVEL_HIGH);
 
     res = pl011_uart_init(spcr->interrupt, spcr->serial_port.address,
-                          PAGE_SIZE);
+                          PAGE_SIZE, sbsa);
     if ( res < 0 )
     {
         printk("pl011: Unable to initialize\n");
@@ -344,6 +340,16 @@ ACPI_DEVICE_START(apl011, "PL011 UART", DEVICE_SERIAL)
         .class_type = ACPI_DBG2_PL011,
         .init = pl011_acpi_uart_init,
 ACPI_DEVICE_END
+
+ACPI_DEVICE_START(asbsa_uart, "SBSA UART", DEVICE_SERIAL)
+        .class_type = ACPI_DBG2_SBSA,
+        .init = pl011_acpi_uart_init,
+ACPI_DEVICE_END
+
+ACPI_DEVICE_START(asbsa32_uart, "SBSA32 UART", DEVICE_SERIAL)
+        .class_type = ACPI_DBG2_SBSA_32,
+        .init = pl011_acpi_uart_init,
+ACPI_DEVICE_END
 #endif
 
 /*
-- 
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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