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3cc5752a69
The goal was to reduce common setup of messages. Changes: * MailBox turned into singleton to follow existing patterns * Removed device specific messages from MailBox requiring clients to know the details instead * Created base Message class which clients should deriver from It really simplify the usage for more complicated message queues like framebuffer setup - see followup commits.
108 lines
3.3 KiB
C++
108 lines
3.3 KiB
C++
/*
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* Copyright (c) 2021, Nico Weber <thakis@chromium.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <Kernel/Prekernel/Arch/aarch64/MMIO.h>
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#include <Kernel/Prekernel/Arch/aarch64/Mailbox.h>
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namespace Prekernel {
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// There's one mailbox at MBOX_BASE_OFFSET for reading responses from VideoCore, and one at MBOX_BASE_OFFSET + 0x20 for sending requests.
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// Each has its own status word.
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constexpr u32 MBOX_BASE_OFFSET = 0xB880;
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constexpr u32 MBOX_0 = MBOX_BASE_OFFSET;
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constexpr u32 MBOX_1 = MBOX_BASE_OFFSET + 0x20;
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constexpr u32 MBOX_READ_DATA = MBOX_0;
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constexpr u32 MBOX_READ_POLL = MBOX_0 + 0x10;
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constexpr u32 MBOX_READ_SENDER = MBOX_0 + 0x14;
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constexpr u32 MBOX_READ_STATUS = MBOX_0 + 0x18;
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constexpr u32 MBOX_READ_CONFIG = MBOX_0 + 0x1C;
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constexpr u32 MBOX_WRITE_DATA = MBOX_1;
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constexpr u32 MBOX_WRITE_STATUS = MBOX_1 + 0x18;
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constexpr u32 MBOX_RESPONSE_SUCCESS = 0x8000'0000;
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constexpr u32 MBOX_RESPONSE_PARTIAL = 0x8000'0001;
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constexpr u32 MBOX_REQUEST = 0;
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constexpr u32 MBOX_FULL = 0x8000'0000;
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constexpr u32 MBOX_EMPTY = 0x4000'0000;
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constexpr int ARM_TO_VIDEOCORE_CHANNEL = 8;
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Mailbox::Message::Message(u32 tag, u32 arguments_size)
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{
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m_tag = tag;
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m_arguments_size = arguments_size;
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m_command_tag = MBOX_REQUEST;
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}
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Mailbox::MessageHeader::MessageHeader()
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{
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m_message_queue_size = 0;
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m_command_tag = MBOX_REQUEST;
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}
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bool Mailbox::MessageHeader::success() const
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{
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return m_command_tag == MBOX_RESPONSE_SUCCESS;
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}
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Mailbox& Mailbox::the()
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{
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static Mailbox instance;
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return instance;
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}
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static void wait_until_we_can_write(MMIO& mmio)
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{
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// Since nothing else writes to the mailbox, this wait is mostly cargo-culted.
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// Most baremetal tutorials on the internet query MBOX_READ_STATUS here, which I think is incorrect and only works because this wait really isn't needed.
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while (mmio.read(MBOX_WRITE_STATUS) & MBOX_FULL)
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;
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}
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static void wait_for_reply(MMIO& mmio)
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{
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while (mmio.read(MBOX_READ_STATUS) & MBOX_EMPTY)
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;
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}
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bool Mailbox::send_queue(void* queue, u32 queue_size) const
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{
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// According to Raspberry Pi specs this is the only channel implemented.
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const u32 channel = ARM_TO_VIDEOCORE_CHANNEL;
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auto message_header = reinterpret_cast<MessageHeader*>(queue);
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message_header->set_queue_size(queue_size);
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auto& mmio = MMIO::the();
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// The mailbox interface has a FIFO for message deliverly in both directions.
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// Responses can be delivered out of order to requests, but we currently ever only send on request at once.
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// It'd be nice to have an async interface here where we send a message, then return immediately, and read the response when an interrupt arrives.
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// But for now, this is synchronous.
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wait_until_we_can_write(mmio);
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// The mailbox message is 32-bit based, so this assumes that message is in the first 4 GiB.
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u32 request = static_cast<u32>(reinterpret_cast<FlatPtr>(queue) & ~0xF) | (channel & 0xF);
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mmio.write(MBOX_WRITE_DATA, request);
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for (;;) {
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wait_for_reply(mmio);
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u32 response = mmio.read(MBOX_READ_DATA);
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// We keep at most one message in flight and do synchronous communication, so response will always be == request for us.
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if (response == request)
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return message_header->success();
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}
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return true;
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}
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}
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