Use flexible array to simplify memory allocation.
It saves some memory, avoids an indirection when reading the 'clusters'
array and removes some LoC.
Detailed explanation:
====================
Knowing that:
- each devm_ allocation over-allocates 40 bytes for internal needs
- Some rounding is done by the memory allocator on 8, 16, 32, 64, 96,
128, 192, 256, 512, 1024, 2048, 4096, 8192 boundaries
and that:
- sizeof(struct tegra186_cpufreq_data) = 24
- sizeof(struct tegra186_cpufreq_cluster) = 16
Memory allocations in tegra186_cpufreq_probe() are:
data: (24 + 40) = 64 => 64 bytes
data->clusters: (2 * 16 + 40) = 72 => 96 bytes
So a total of 160 bytes are allocated.
56 for the real need, 80 for internal uses and 24 are wasted.
If 'struct tegra186_cpufreq_data' is reordered so that 'clusters' is a
flexible array:
- it saves one pointer in the structure
- only one allocation is needed
So, only 96 bytes are allocated:
16 + 2 * 16 + 40 = 88 => 96 bytes
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
Compile tested only
---
drivers/cpufreq/tegra186-cpufreq.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/drivers/cpufreq/tegra186-cpufreq.c b/drivers/cpufreq/tegra186-cpufreq.c
index 6c88827f4e62..f98f53bf1011 100644
--- a/drivers/cpufreq/tegra186-cpufreq.c
+++ b/drivers/cpufreq/tegra186-cpufreq.c
@@ -65,8 +65,8 @@ struct tegra186_cpufreq_cluster {
struct tegra186_cpufreq_data {
void __iomem *regs;
- struct tegra186_cpufreq_cluster *clusters;
const struct tegra186_cpufreq_cpu *cpus;
+ struct tegra186_cpufreq_cluster clusters[];
};
static int tegra186_cpufreq_init(struct cpufreq_policy *policy)
@@ -221,15 +221,12 @@ static int tegra186_cpufreq_probe(struct platform_device *pdev)
struct tegra_bpmp *bpmp;
unsigned int i = 0, err;
- data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+ data = devm_kzalloc(&pdev->dev,
+ struct_size(data, clusters, TEGRA186_NUM_CLUSTERS),
+ GFP_KERNEL);
if (!data)
return -ENOMEM;
- data->clusters = devm_kcalloc(&pdev->dev, TEGRA186_NUM_CLUSTERS,
- sizeof(*data->clusters), GFP_KERNEL);
- if (!data->clusters)
- return -ENOMEM;
-
data->cpus = tegra186_cpus;
bpmp = tegra_bpmp_get(&pdev->dev);
--
2.34.1
