Commit 2790e2a3 authored by Frank Oltmanns's avatar Frank Oltmanns Committed by Stephen Boyd
Browse files

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: default avatarFrank 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: default avatarStephen Boyd <sboyd@kernel.org>
parent 2e9abc6e

drivers/clk/.kunitconfig

+1 −0
Original line number Diff line number Diff line
@@ -2,4 +2,5 @@ CONFIG_KUNIT=y 
CONFIG_COMMON_CLK=y

CONFIG_CLK_KUNIT_TEST=y

CONFIG_CLK_GATE_KUNIT_TEST=y

CONFIG_CLK_FD_KUNIT_TEST=y

CONFIG_UML_PCI_OVER_VIRTIO=n

drivers/clk/Kconfig

+7 −0
Original line number Diff line number Diff line
@@ -517,4 +517,11 @@ config CLK_GATE_KUNIT_TEST 
	help

	  Kunit test for the basic clk gate type.



config CLK_FD_KUNIT_TEST

	tristate "Basic fractional divider type Kunit test" if !KUNIT_ALL_TESTS

	depends on KUNIT

	default KUNIT_ALL_TESTS

	help

	  Kunit test for the clk-fractional-divider type.



endif

drivers/clk/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ obj-$(CONFIG_COMMON_CLK) += clk-multiplier.o 
obj-$(CONFIG_COMMON_CLK)	+= clk-mux.o

obj-$(CONFIG_COMMON_CLK)	+= clk-composite.o

obj-$(CONFIG_COMMON_CLK)	+= clk-fractional-divider.o

obj-$(CONFIG_CLK_FD_KUNIT_TEST) += clk-fractional-divider_test.o

obj-$(CONFIG_COMMON_CLK)	+= clk-gpio.o

ifeq ($(CONFIG_OF), y)

obj-$(CONFIG_COMMON_CLK)	+= clk-conf.o

drivers/clk/clk-fractional-divider_test.c

0 → 100644
+147 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * Kunit test for clock fractional divider

 */

#include <linux/clk-provider.h>

#include <kunit/test.h>



#include "clk-fractional-divider.h"



/*

 * Test the maximum denominator case for fd clock without flags.

 *

 * Expect the highest possible denominator to be used in order to get as close as possible to the

 * requested rate.

 */

static void clk_fd_test_approximation_max_denominator(struct kunit *test)

{

	struct clk_fractional_divider *fd;

	unsigned long rate, parent_rate, parent_rate_before, m, n, max_n;



	fd = kunit_kzalloc(test, sizeof(*fd), GFP_KERNEL);

	KUNIT_ASSERT_NOT_NULL(test, fd);



	fd->mwidth = 3;

	fd->nwidth = 3;

	max_n = 7;



	rate = 240000000;

	parent_rate = (max_n + 1) * rate; /* so that it exceeds the maximum divisor */

	parent_rate_before = parent_rate;



	clk_fractional_divider_general_approximation(&fd->hw, rate, &parent_rate, &m, &n);

	KUNIT_ASSERT_EQ(test, parent_rate, parent_rate_before);



	KUNIT_EXPECT_EQ(test, m, 1);

	KUNIT_EXPECT_EQ(test, n, max_n);

}



/*

 * Test the maximum numerator case for fd clock without flags.

 *

 * Expect the highest possible numerator to be used in order to get as close as possible to the

 * requested rate.

 */

static void clk_fd_test_approximation_max_numerator(struct kunit *test)

{

	struct clk_fractional_divider *fd;

	unsigned long rate, parent_rate, parent_rate_before, m, n, max_m;



	fd = kunit_kzalloc(test, sizeof(*fd), GFP_KERNEL);

	KUNIT_ASSERT_NOT_NULL(test, fd);



	fd->mwidth = 3;

	max_m = 7;

	fd->nwidth = 3;



	rate = 240000000;

	parent_rate = rate / (max_m + 1); /* so that it exceeds the maximum numerator */

	parent_rate_before = parent_rate;



	clk_fractional_divider_general_approximation(&fd->hw, rate, &parent_rate, &m, &n);

	KUNIT_ASSERT_EQ(test, parent_rate, parent_rate_before);



	KUNIT_EXPECT_EQ(test, m, max_m);

	KUNIT_EXPECT_EQ(test, n, 1);

}



/*

 * Test the maximum denominator case for zero based fd clock.

 *

 * Expect the highest possible denominator to be used in order to get as close as possible to the

 * requested rate.

 */

static void clk_fd_test_approximation_max_denominator_zero_based(struct kunit *test)

{

	struct clk_fractional_divider *fd;

	unsigned long rate, parent_rate, parent_rate_before, m, n, max_n;



	fd = kunit_kzalloc(test, sizeof(*fd), GFP_KERNEL);

	KUNIT_ASSERT_NOT_NULL(test, fd);



	fd->flags = CLK_FRAC_DIVIDER_ZERO_BASED;

	fd->mwidth = 3;

	fd->nwidth = 3;

	max_n = 8;



	rate = 240000000;

	parent_rate = (max_n + 1) * rate; /* so that it exceeds the maximum divisor */

	parent_rate_before = parent_rate;



	clk_fractional_divider_general_approximation(&fd->hw, rate, &parent_rate, &m, &n);

	KUNIT_ASSERT_EQ(test, parent_rate, parent_rate_before);



	KUNIT_EXPECT_EQ(test, m, 1);

	KUNIT_EXPECT_EQ(test, n, max_n);

}



/*

 * Test the maximum numerator case for zero based fd clock.

 *

 * Expect the highest possible numerator to be used in order to get as close as possible to the

 * requested rate.

 */

static void clk_fd_test_approximation_max_numerator_zero_based(struct kunit *test)

{

	struct clk_fractional_divider *fd;

	unsigned long rate, parent_rate, parent_rate_before, m, n, max_m;



	fd = kunit_kzalloc(test, sizeof(*fd), GFP_KERNEL);

	KUNIT_ASSERT_NOT_NULL(test, fd);



	fd->flags = CLK_FRAC_DIVIDER_ZERO_BASED;

	fd->mwidth = 3;

	max_m = 8;

	fd->nwidth = 3;



	rate = 240000000;

	parent_rate = rate / (max_m + 1); /* so that it exceeds the maximum numerator */

	parent_rate_before = parent_rate;



	clk_fractional_divider_general_approximation(&fd->hw, rate, &parent_rate, &m, &n);

	KUNIT_ASSERT_EQ(test, parent_rate, parent_rate_before);



	KUNIT_EXPECT_EQ(test, m, max_m);

	KUNIT_EXPECT_EQ(test, n, 1);

}



static struct kunit_case clk_fd_approximation_test_cases[] = {

	KUNIT_CASE(clk_fd_test_approximation_max_denominator),

	KUNIT_CASE(clk_fd_test_approximation_max_numerator),

	KUNIT_CASE(clk_fd_test_approximation_max_denominator_zero_based),

	KUNIT_CASE(clk_fd_test_approximation_max_numerator_zero_based),

	{}

};



/*

 * Test suite for clk_fractional_divider_general_approximation().

 */

static struct kunit_suite clk_fd_approximation_suite = {

	.name = "clk-fd-approximation",

	.test_cases = clk_fd_approximation_test_cases,

};



kunit_test_suites(

	&clk_fd_approximation_suite

);

MODULE_LICENSE("GPL");