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Date: Thu, 02 Apr 2020 13:54:57 +0200
From: Michał Mirosław <mirq-linux@...e.qmqm.pl>
To: Adrian Hunter <adrian.hunter@...el.com>,
Kevin Liu <kliu5@...vell.com>,
Michal Simek <michal.simek@...inx.com>,
Suneel Garapati <suneel.garapati@...inx.com>,
Ulf Hansson <ulf.hansson@...aro.org>
Cc: linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org
Subject: [PATCH 5/7] mmc: sdhci: simplify clock frequency calculation
Make clock frequency calculations simpler by replacing loops
with divide-and-clamp.
Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
---
drivers/mmc/host/sdhci.c | 56 +++++++++++++++++++---------------------
drivers/mmc/host/sdhci.h | 4 +--
2 files changed, 29 insertions(+), 31 deletions(-)
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index ed88ac4e4cf3..d750c0997c3f 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1756,10 +1756,13 @@ static u16 sdhci_get_preset_value(struct sdhci_host *host)
u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
unsigned int *actual_clock)
{
- int div = 0; /* Initialized for compiler warning */
+ unsigned int div = 0; /* Initialized for compiler warning */
int real_div = div, clk_mul = 1;
u16 clk = 0;
- bool switch_base_clk = false;
+ bool use_base_clk;
+
+ if (clock == 0)
+ unreachable();
if (host->version >= SDHCI_SPEC_300) {
if (host->preset_enabled) {
@@ -1781,13 +1784,12 @@ u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
* Check if the Host Controller supports Programmable Clock
* Mode.
*/
- if (host->clk_mul) {
- for (div = 1; div <= 1024; div++) {
- if ((host->max_clk * host->clk_mul / div)
- <= clock)
- break;
- }
- if ((host->max_clk * host->clk_mul / div) <= clock) {
+ use_base_clk = !host->clk_mul;
+
+ if (!use_base_clk) {
+ div = DIV_ROUND_UP(host->max_clk * host->clk_mul, clock);
+
+ if (div <= SDHCI_MAX_DIV_SPEC_300 / 2 + 1) {
/*
* Set Programmable Clock Mode in the Clock
* Control register.
@@ -1798,35 +1800,31 @@ u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
div--;
} else {
/*
- * Divisor can be too small to reach clock
- * speed requirement. Then use the base clock.
+ * Divisor is too big for requested clock rate.
+ * Use the base clock, then.
*/
- switch_base_clk = true;
+ use_base_clk = true;
}
}
- if (!host->clk_mul || switch_base_clk) {
- /* Version 3.00 divisors must be a multiple of 2. */
- if (host->max_clk <= clock) {
- div = 1;
- if (host->quirks2 & SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN)
- div = 2;
- } else {
- for (div = 2; div < SDHCI_MAX_DIV_SPEC_300;
- div += 2) {
- if ((host->max_clk / div) <= clock)
- break;
- }
+ if (use_base_clk) {
+ /* Version 3.00 divisors must be 1 or a multiple of 2. */
+ div = DIV_ROUND_UP(host->max_clk, clock);
+ if (div > 1) {
+ div = min(div, SDHCI_MAX_DIV_SPEC_300);
+ div = round_up(div, 2);
}
- real_div = div;
div >>= 1;
+ if (host->quirks2 & SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN)
+ div += !div;
+
+ real_div = div * 2 + !div;
}
} else {
/* Version 2.00 divisors must be a power of 2. */
- for (div = 1; div < SDHCI_MAX_DIV_SPEC_200; div *= 2) {
- if ((host->max_clk / div) <= clock)
- break;
- }
+ div = DIV_ROUND_UP(host->max_clk, clock);
+ div = min(div, SDHCI_MAX_DIV_SPEC_200);
+ div = roundup_pow_of_two(div);
real_div = div;
div >>= 1;
}
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 79dffbb731d3..ea8aabb3bf16 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -290,8 +290,8 @@
* End of controller registers.
*/
-#define SDHCI_MAX_DIV_SPEC_200 256
-#define SDHCI_MAX_DIV_SPEC_300 2046
+#define SDHCI_MAX_DIV_SPEC_200 256u
+#define SDHCI_MAX_DIV_SPEC_300 2046u
/*
* Host SDMA buffer boundary. Valid values from 4K to 512K in powers of 2.
--
2.20.1
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