[PATCH 24/27 v8] xen/arm: vpl011: Add a pl011 uart DT node in the guest device tree

[Bhupinder Thakur <bhupinder.thakur@linaro.org>]

The SBSA UART node format is as specified in
Documentation/devicetree/bindings/serial/arm_sbsa_uart.txt and given below:

ARM SBSA defined generic UART
------------------------------
This UART uses a subset of the PL011 registers and consequently lives
in the PL011 driver. It's baudrate and other communication parameters
cannot be adjusted at runtime, so it lacks a clock specifier here.

Required properties:
- compatible: must be "arm,sbsa-uart"
- reg: exactly one register range
- interrupts: exactly one interrupt specifier
- current-speed: the (fixed) baud rate set by the firmware

Currently the baud rate of 115200 has been selected as a default value,
which is one of the valid baud rate settings. Higher baud rate was
selected since an emulated pl011 can support any valid baud rate without
any limitation of the hardware.

Signed-off-by: Bhupinder Thakur <bhupinder.thakur@linaro.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: Wei Liu <wei.liu2@citrix.com>
---
CC: Ian Jackson <ian.jackson@eu.citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien.grall@arm.com>

Changes since v7:
- Added a TODO to avoid conflict between vpl011 irq and user specified irqs.
- Used a new bool vuart_enabled to explicitly set whether pl011 UART is enabled/disabled.

Changes since v6:
- Added a comment explaining why user specified IRQ should not conflict with vpl011
  SPI.
- Checking the vuart type explicitly against vpl011 enum type.
- Removed uart-compat string and using "arm,sbsa-uart" string directly.
- I have retained the reviewed-by/acked-by tags as these are minor changes.

 tools/libxl/libxl_arm.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c
index b8147f0..c0e496f 100644
--- a/tools/libxl/libxl_arm.c
+++ b/tools/libxl/libxl_arm.c
@@ -43,11 +43,38 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
 {
     uint32_t nr_spis = 0;
     unsigned int i;
+    uint32_t vuart_irq;
+    bool vuart_enabled = false;
+
+    /*
+     * If pl011 vuart is enabled then increment the nr_spis to allow allocation
+     * of SPI VIRQ for pl011.
+     */
+    if (d_config->b_info.arch_arm.vuart == LIBXL_VUART_TYPE_SBSA_UART) {
+        nr_spis += (GUEST_VPL011_SPI - 32) + 1;
+        vuart_irq = GUEST_VPL011_SPI;
+        vuart_enabled = true;
+    }
 
     for (i = 0; i < d_config->b_info.num_irqs; i++) {
         uint32_t irq = d_config->b_info.irqs[i];
         uint32_t spi;
 
+        /*
+         * This check ensures the if user has requested pass-through of a certain irq
+         * which conflicts with vpl011 irq then it flags an error to indicate to the
+         * user that the specific HW irq cannot be used as it is dedicated for vpl011.
+         * 
+         * TODO:
+         * The vpl011 irq should be assigned such that it never conflicts with user
+         * specified irqs thereby preventing its pass-through. This TODO is for
+         * implementing that logic in future.
+         */
+        if (vuart_enabled && irq == vuart_irq) {
+            LOG(ERROR, "Physical IRQ %u conflicting with pl011 SPI\n", irq);
+            return ERROR_FAIL;
+        }
+
         if (irq < 32)
             continue;
 
@@ -590,6 +617,38 @@ static int make_hypervisor_node(libxl__gc *gc, void *fdt,
     return 0;
 }
 
+static int make_vpl011_uart_node(libxl__gc *gc, void *fdt,
+                                 const struct arch_info *ainfo,
+                                 struct xc_dom_image *dom)
+{
+    int res;
+    gic_interrupt intr;
+
+    res = fdt_begin_node(fdt, "sbsa-pl011");
+    if (res) return res;
+
+    res = fdt_property_compat(gc, fdt, 1, "arm,sbsa-uart");
+    if (res) return res;
+
+    res = fdt_property_regs(gc, fdt, ROOT_ADDRESS_CELLS, ROOT_SIZE_CELLS,
+                            1,
+                            GUEST_PL011_BASE, GUEST_PL011_SIZE);
+    if (res) return res;
+
+    set_interrupt(intr, GUEST_VPL011_SPI, 0xf, DT_IRQ_TYPE_LEVEL_HIGH);
+
+    res = fdt_property_interrupts(gc, fdt, &intr, 1);
+    if (res) return res;
+
+    /* Use a default baud rate of 115200. */
+    fdt_property_u32(fdt, "current-speed", 115200);
+
+    res = fdt_end_node(fdt);
+    if (res) return res;
+
+    return 0;
+}
+
 static const struct arch_info *get_arch_info(libxl__gc *gc,
                                              const struct xc_dom_image *dom)
 {
@@ -889,6 +948,9 @@ next_resize:
         FDT( make_timer_node(gc, fdt, ainfo, xc_config->clock_frequency) );
         FDT( make_hypervisor_node(gc, fdt, vers) );
 
+        if (info->arch_arm.vuart == LIBXL_VUART_TYPE_SBSA_UART)
+            FDT( make_vpl011_uart_node(gc, fdt, ainfo, dom) );
+
         if (pfdt)
             FDT( copy_partial_fdt(gc, fdt, pfdt) );
 
-- 
2.7.4


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