From 32eb6453328c372a11559a21a53e5280ad44a421 Mon Sep 17 00:00:00 2001 From: Christophe JAILLET Date: Sun, 20 Nov 2022 18:19:02 +0100 Subject: [PATCH] cpufreq: tegra186: Use flexible array to simplify memory allocation 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 Signed-off-by: Viresh Kumar --- 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 6c88827..f98f53b 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); -- 2.7.4