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Frank Oltmannsbebarino
Frank Oltmanns
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bebarino
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clk: fractional-divider: tests: Add test suite for edge cases
In light of the recent discovery that the fractional divisor approximation does not utilize the full available range for clocks that are flagged CLK_FRAC_DIVIDER_ZERO_BASED [1], implement tests for the edge cases of this clock type. Signed-off-by: Frank Oltmanns <frank@oltmanns.dev> Link: https://lore.kernel.org/lkml/20230529133433.56215-1-frank@oltmanns.dev [1] Link: https://lore.kernel.org/r/20230617131041.18313-3-frank@oltmanns.dev [sboyd@kernel.org: Rename suite and tests slightly, drop unused includes, store parent rate to compare instead of repeating equation] Signed-off-by: Stephen Boyd <sboyd@kernel.org>
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‎drivers/clk/.kunitconfig

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@@ -2,4 +2,5 @@ CONFIG_KUNIT=y
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CONFIG_COMMON_CLK=y
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CONFIG_CLK_KUNIT_TEST=y
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CONFIG_CLK_GATE_KUNIT_TEST=y
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CONFIG_CLK_FD_KUNIT_TEST=y
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CONFIG_UML_PCI_OVER_VIRTIO=n

‎drivers/clk/Kconfig

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@@ -517,4 +517,11 @@ config CLK_GATE_KUNIT_TEST
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help
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Kunit test for the basic clk gate type.
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config CLK_FD_KUNIT_TEST
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tristate "Basic fractional divider type Kunit test" if !KUNIT_ALL_TESTS
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depends on KUNIT
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default KUNIT_ALL_TESTS
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help
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Kunit test for the clk-fractional-divider type.
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endif

‎drivers/clk/Makefile

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@@ -12,6 +12,7 @@ obj-$(CONFIG_COMMON_CLK) += clk-multiplier.o
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obj-$(CONFIG_COMMON_CLK) += clk-mux.o
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obj-$(CONFIG_COMMON_CLK) += clk-composite.o
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obj-$(CONFIG_COMMON_CLK) += clk-fractional-divider.o
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obj-$(CONFIG_CLK_FD_KUNIT_TEST) += clk-fractional-divider_test.o
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obj-$(CONFIG_COMMON_CLK) += clk-gpio.o
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ifeq ($(CONFIG_OF), y)
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obj-$(CONFIG_COMMON_CLK) += clk-conf.o

‎drivers/clk/clk-fractional-divider_test.c

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// SPDX-License-Identifier: GPL-2.0
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/*
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* Kunit test for clock fractional divider
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*/
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#include <linux/clk-provider.h>
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#include <kunit/test.h>
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#include "clk-fractional-divider.h"
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/*
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* Test the maximum denominator case for fd clock without flags.
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*
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* Expect the highest possible denominator to be used in order to get as close as possible to the
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* requested rate.
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*/
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static void clk_fd_test_approximation_max_denominator(struct kunit *test)
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{
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struct clk_fractional_divider *fd;
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unsigned long rate, parent_rate, parent_rate_before, m, n, max_n;
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fd = kunit_kzalloc(test, sizeof(*fd), GFP_KERNEL);
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KUNIT_ASSERT_NOT_NULL(test, fd);
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fd->mwidth = 3;
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fd->nwidth = 3;
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max_n = 7;
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rate = 240000000;
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parent_rate = (max_n + 1) * rate; /* so that it exceeds the maximum divisor */
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parent_rate_before = parent_rate;
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clk_fractional_divider_general_approximation(&fd->hw, rate, &parent_rate, &m, &n);
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KUNIT_ASSERT_EQ(test, parent_rate, parent_rate_before);
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KUNIT_EXPECT_EQ(test, m, 1);
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KUNIT_EXPECT_EQ(test, n, max_n);
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}
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/*
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* Test the maximum numerator case for fd clock without flags.
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*
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* Expect the highest possible numerator to be used in order to get as close as possible to the
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* requested rate.
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*/
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static void clk_fd_test_approximation_max_numerator(struct kunit *test)
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{
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struct clk_fractional_divider *fd;
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unsigned long rate, parent_rate, parent_rate_before, m, n, max_m;
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fd = kunit_kzalloc(test, sizeof(*fd), GFP_KERNEL);
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KUNIT_ASSERT_NOT_NULL(test, fd);
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fd->mwidth = 3;
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max_m = 7;
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fd->nwidth = 3;
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rate = 240000000;
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parent_rate = rate / (max_m + 1); /* so that it exceeds the maximum numerator */
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parent_rate_before = parent_rate;
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clk_fractional_divider_general_approximation(&fd->hw, rate, &parent_rate, &m, &n);
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KUNIT_ASSERT_EQ(test, parent_rate, parent_rate_before);
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KUNIT_EXPECT_EQ(test, m, max_m);
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KUNIT_EXPECT_EQ(test, n, 1);
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}
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/*
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* Test the maximum denominator case for zero based fd clock.
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*
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* Expect the highest possible denominator to be used in order to get as close as possible to the
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* requested rate.
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*/
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static void clk_fd_test_approximation_max_denominator_zero_based(struct kunit *test)
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{
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struct clk_fractional_divider *fd;
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unsigned long rate, parent_rate, parent_rate_before, m, n, max_n;
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fd = kunit_kzalloc(test, sizeof(*fd), GFP_KERNEL);
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KUNIT_ASSERT_NOT_NULL(test, fd);
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fd->flags = CLK_FRAC_DIVIDER_ZERO_BASED;
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fd->mwidth = 3;
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fd->nwidth = 3;
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max_n = 8;
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rate = 240000000;
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parent_rate = (max_n + 1) * rate; /* so that it exceeds the maximum divisor */
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parent_rate_before = parent_rate;
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clk_fractional_divider_general_approximation(&fd->hw, rate, &parent_rate, &m, &n);
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KUNIT_ASSERT_EQ(test, parent_rate, parent_rate_before);
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KUNIT_EXPECT_EQ(test, m, 1);
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KUNIT_EXPECT_EQ(test, n, max_n);
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}
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/*
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* Test the maximum numerator case for zero based fd clock.
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*
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* Expect the highest possible numerator to be used in order to get as close as possible to the
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* requested rate.
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*/
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static void clk_fd_test_approximation_max_numerator_zero_based(struct kunit *test)
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{
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struct clk_fractional_divider *fd;
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unsigned long rate, parent_rate, parent_rate_before, m, n, max_m;
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fd = kunit_kzalloc(test, sizeof(*fd), GFP_KERNEL);
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KUNIT_ASSERT_NOT_NULL(test, fd);
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fd->flags = CLK_FRAC_DIVIDER_ZERO_BASED;
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fd->mwidth = 3;
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max_m = 8;
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fd->nwidth = 3;
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rate = 240000000;
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parent_rate = rate / (max_m + 1); /* so that it exceeds the maximum numerator */
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parent_rate_before = parent_rate;
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clk_fractional_divider_general_approximation(&fd->hw, rate, &parent_rate, &m, &n);
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KUNIT_ASSERT_EQ(test, parent_rate, parent_rate_before);
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KUNIT_EXPECT_EQ(test, m, max_m);
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KUNIT_EXPECT_EQ(test, n, 1);
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}
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static struct kunit_case clk_fd_approximation_test_cases[] = {
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KUNIT_CASE(clk_fd_test_approximation_max_denominator),
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KUNIT_CASE(clk_fd_test_approximation_max_numerator),
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KUNIT_CASE(clk_fd_test_approximation_max_denominator_zero_based),
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KUNIT_CASE(clk_fd_test_approximation_max_numerator_zero_based),
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{}
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};
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/*
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* Test suite for clk_fractional_divider_general_approximation().
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*/
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static struct kunit_suite clk_fd_approximation_suite = {
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.name = "clk-fd-approximation",
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.test_cases = clk_fd_approximation_test_cases,
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};
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kunit_test_suites(
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&clk_fd_approximation_suite
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);
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MODULE_LICENSE("GPL");

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