Re: QEMU RISC-V virt machine poweroff driver

From: Anup Patel <anup@brainfault.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Sebastian Reichel <sre@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	devicetree@vger.kernel.org,
	linux-riscv <linux-riscv@lists.infradead.org>,
	linux-pm@vger.kernel.org
Subject: Re: QEMU RISC-V virt machine poweroff driver
Date: Mon, 11 Nov 2019 17:06:24 +0530	[thread overview]
Message-ID: <CAAhSdy3SGAkOFMhx320KJdPDh6c=qcKqCZ=qrXNKBGtejpZwSA@mail.gmail.com> (raw)
In-Reply-To: <20191107212408.11857-1-hch@lst.de>

On Fri, Nov 8, 2019 at 2:54 AM Christoph Hellwig <hch@lst.de> wrote:
>
> Hi all,
>
> this patch add a driver for the test device in the Qemu RISC-V
> virt machine which allows properly shutting down the VM.
> It also is added to the riscv defconfig given that qemu-virt
> is the most popular riscv platform.

We really don't need this driver. Instead, we can simply re-use
following drivers:
mfd/syscon
power/reset/syscon-reboot
power/reset/syscon-poweroff

Just enable following to your defconfig:
CONFIG_POWER_RESET=y
CONFIG_POWER_RESET_SYSCON=y
CONFIG_POWER_RESET_SYSCON_POWEROFF=y
CONFIG_SYSCON_REBOOT_MODE=y


Once above drivers are enabled in your defconfig, make sure
test device DT nodes are described in the following way for virt machine:

testdev: test@100000 {
    compatible = "syscon";
    reg = <0x100000 0x1000>;
};

reboot {
    compatible = "syscon-reboot";
    regmap = <&testdev>;
    offset = <0x0>;
    value = <0x7777>;
};

poweroff {
    compatible = "syscon-poweroff";
    regmap = <&testdev>;
    offset = <0x0>;
    value = <0x5555>;
};


Here's the QEMU changes I used for above DT nodes:

diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index d7c5d630eb..7f8206c726 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -186,7 +186,7 @@ static void create_fdt(RISCVVirtState *s, const
struct MemmapEntry *memmap,
     int cpu;
     uint32_t *cells;
     char *nodename;
-    uint32_t plic_phandle, phandle = 1;
+    uint32_t plic_phandle, test_phandle, phandle = 1;
     int i;
     hwaddr flashsize = virt_memmap[VIRT_FLASH].size / 2;
     hwaddr flashbase = virt_memmap[VIRT_FLASH].base;
@@ -357,13 +357,32 @@ static void create_fdt(RISCVVirtState *s, const
struct MemmapEntry *memmap,
     create_pcie_irq_map(fdt, nodename, plic_phandle);
     g_free(nodename);

+    test_phandle = phandle++;
     nodename = g_strdup_printf("/test@%lx",
         (long)memmap[VIRT_TEST].base);
     qemu_fdt_add_subnode(fdt, nodename);
-    qemu_fdt_setprop_string(fdt, nodename, "compatible", "sifive,test0");
+    qemu_fdt_setprop_string(fdt, nodename, "compatible", "syscon");
     qemu_fdt_setprop_cells(fdt, nodename, "reg",
         0x0, memmap[VIRT_TEST].base,
         0x0, memmap[VIRT_TEST].size);
+    qemu_fdt_setprop_cell(fdt, nodename, "phandle", test_phandle);
+    test_phandle = qemu_fdt_get_phandle(fdt, nodename);
+    g_free(nodename);
+
+    nodename = g_strdup_printf("/reboot");
+    qemu_fdt_add_subnode(fdt, nodename);
+    qemu_fdt_setprop_string(fdt, nodename, "compatible", "syscon-reboot");
+    qemu_fdt_setprop_cell(fdt, nodename, "regmap", test_phandle);
+    qemu_fdt_setprop_cell(fdt, nodename, "offset", 0x0);
+    qemu_fdt_setprop_cell(fdt, nodename, "value", FINISHER_RESET);
+    g_free(nodename);
+
+    nodename = g_strdup_printf("/poweroff");
+    qemu_fdt_add_subnode(fdt, nodename);
+    qemu_fdt_setprop_string(fdt, nodename, "compatible", "syscon-poweroff");
+    qemu_fdt_setprop_cell(fdt, nodename, "regmap", test_phandle);
+    qemu_fdt_setprop_cell(fdt, nodename, "offset", 0x0);
+    qemu_fdt_setprop_cell(fdt, nodename, "value", FINISHER_PASS);
     g_free(nodename);

     nodename = g_strdup_printf("/uart@%lx",


Regards,
Anup


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