pw_kvs/flash_memory.cc

// Copyright 2020 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.

#define PW_LOG_MODULE_NAME "PW_FLASH"
#define PW_LOG_LEVEL PW_KVS_LOG_LEVEL

#include "pw_kvs/flash_memory.h"

#include <algorithm>
#include <cinttypes>
#include <cstring>

#include "pw_assert/check.h"
#include "pw_kvs_private/config.h"
#include "pw_log/log.h"
#include "pw_status/status_with_size.h"
#include "pw_status/try.h"

namespace pw::kvs {

using std::byte;

#if PW_CXX_STANDARD_IS_SUPPORTED(17)

Status FlashPartition::Writer::DoWrite(ConstByteSpan data) {
  if (partition_.size_bytes() <= position_) {
    return Status::OutOfRange();
  }
  if (data.size_bytes() > (partition_.size_bytes() - position_)) {
    return Status::ResourceExhausted();
  }
  if (data.size_bytes() == 0) {
    return OkStatus();
  }

  const StatusWithSize sws = partition_.Write(position_, data);
  if (sws.ok()) {
    position_ += data.size_bytes();
  }
  return sws.status();
}

StatusWithSize FlashPartition::Reader::DoRead(ByteSpan data) {
  if (position_ >= partition_.size_bytes()) {
    return StatusWithSize::OutOfRange();
  }

  size_t bytes_to_read =
      std::min(data.size_bytes(), partition_.size_bytes() - position_);

  const StatusWithSize sws =
      partition_.Read(position_, data.first(bytes_to_read));
  if (sws.ok()) {
    position_ += bytes_to_read;
  }
  return sws;
}

#endif  // PW_CXX_STANDARD_IS_SUPPORTED(17)

StatusWithSize FlashPartition::Output::DoWrite(span<const byte> data) {
  PW_TRY_WITH_SIZE(flash_.Write(address_, data));
  address_ += data.size();
  return StatusWithSize(data.size());
}

StatusWithSize FlashPartition::Input::DoRead(span<byte> data) {
  StatusWithSize result = flash_.Read(address_, data);
  address_ += result.size();
  return result;
}

FlashPartition::FlashPartition(
    FlashMemory* flash,
    uint32_t flash_start_sector_index,
    uint32_t flash_sector_count,
    uint32_t alignment_bytes,  // Defaults to flash alignment
    PartitionPermission permission)

    : flash_(*flash),
      flash_sector_count_(flash_sector_count),
      flash_start_sector_index_(flash_start_sector_index),
      alignment_bytes_(
          alignment_bytes == 0
              ? flash_.alignment_bytes()
              : std::max(alignment_bytes, uint32_t(flash_.alignment_bytes()))),
      permission_(permission) {
  uint32_t misalignment = (alignment_bytes_ % flash_.alignment_bytes());
  PW_DCHECK_UINT_EQ(misalignment,
                    0,
                    "Flash partition alignmentmust be a multiple of the flash "
                    "memory alignment");
}

Status FlashPartition::Erase(Address address, size_t num_sectors) {
  if (permission_ == PartitionPermission::kReadOnly) {
    return Status::PermissionDenied();
  }

  PW_TRY(CheckBounds(address, num_sectors * sector_size_bytes()));
  const size_t address_sector_offset = address % sector_size_bytes();
  PW_CHECK_UINT_EQ(address_sector_offset, 0u);

  return flash_.Erase(PartitionToFlashAddress(address), num_sectors);
}

StatusWithSize FlashPartition::Read(Address address, span<byte> output) {
  PW_TRY_WITH_SIZE(CheckBounds(address, output.size()));
  return flash_.Read(PartitionToFlashAddress(address), output);
}

StatusWithSize FlashPartition::Write(Address address, span<const byte> data) {
  if (permission_ == PartitionPermission::kReadOnly) {
    return StatusWithSize::PermissionDenied();
  }
  PW_TRY_WITH_SIZE(CheckBounds(address, data.size()));
  const size_t address_alignment_offset = address % alignment_bytes();
  PW_CHECK_UINT_EQ(address_alignment_offset, 0u);
  const size_t size_alignment_offset = data.size() % alignment_bytes();
  PW_CHECK_UINT_EQ(size_alignment_offset, 0u);
  return flash_.Write(PartitionToFlashAddress(address), data);
}

Status FlashPartition::IsRegionErased(Address source_flash_address,
                                      size_t length,
                                      bool* is_erased) {
  // Relying on Read() to check address and len arguments.
  if (is_erased == nullptr) {
    return Status::InvalidArgument();
  }

  // TODO(pwbug/214): Currently using a single flash alignment to do both the
  // read and write. The allowable flash read length may be less than what write
  // needs (possibly by a bunch), resulting in read_buffer and
  // erased_pattern_buffer being bigger than they need to be.
  const size_t alignment = alignment_bytes();
  if (alignment > kMaxFlashAlignment || kMaxFlashAlignment % alignment ||
      length % alignment) {
    return Status::InvalidArgument();
  }

  byte read_buffer[kMaxFlashAlignment];
  const byte erased_byte = flash_.erased_memory_content();
  size_t offset = 0;
  *is_erased = false;
  while (length > 0u) {
    // Check earlier that length is aligned, no need to round up
    size_t read_size = std::min(sizeof(read_buffer), length);
    PW_TRY(
        Read(source_flash_address + offset, read_size, read_buffer).status());

    for (byte b : span(read_buffer, read_size)) {
      if (b != erased_byte) {
        // Detected memory chunk is not entirely erased
        return OkStatus();
      }
    }

    offset += read_size;
    length -= read_size;
  }
  *is_erased = true;
  return OkStatus();
}

bool FlashPartition::AppearsErased(span<const byte> data) const {
  byte erased_content = flash_.erased_memory_content();
  for (byte b : data) {
    if (b != erased_content) {
      return false;
    }
  }
  return true;
}

Status FlashPartition::CheckBounds(Address address, size_t length) const {
  if (address + length > size_bytes()) {
    PW_LOG_ERROR(
        "FlashPartition - Attempted access (address: %u length: %u), exceeds "
        "partition size %u bytes",
        unsigned(address),
        unsigned(length),
        unsigned(size_bytes()));
    return Status::OutOfRange();
  }
  return OkStatus();
}

}  // namespace pw::kvs