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Message-Id: <a8a677659b27244be865a730f6a7f2b7805a4390.1627204633.git.mirq-linux@rere.qmqm.pl>
Date: Sun, 25 Jul 2021 11:20:49 +0200
From: Michał Mirosław <mirq-linux@...e.qmqm.pl>
To: Kevin Liu <kliu5@...vell.com>,
Michal Simek <michal.simek@...inx.com>,
Suneel Garapati <suneel.garapati@...inx.com>,
Ulf Hansson <ulf.hansson@...aro.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>,
linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
Al Cooper <alcooperx@...il.com>
Subject: [PATCH v4 5/5] mmc: sdhci: simplify v2/v3+ clock calculation
For base clock setting, SDHCI V2 differs from V3+ only in allowed divisor
values. Remove the duplicate version of code and reduce indentation
levels. We can see now, that 'real_div' can't be zero, so the check is
removed. While at it, replace divisor search loops with divide-and-clamp
to make the code even more readable.
Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
---
v4: no changes
v3: squashed div-conversion and deduplication patches to avoid code churn
v2: no changes
---
drivers/mmc/host/sdhci.c | 124 ++++++++++++++++++---------------------
drivers/mmc/host/sdhci.h | 4 +-
2 files changed, 58 insertions(+), 70 deletions(-)
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index cfa314e659bc..90bda4150083 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1848,88 +1848,76 @@ 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 */
- int real_div = div, clk_mul = 1;
+ unsigned int div, real_div, clk_mul = 1;
u16 clk = 0;
- bool switch_base_clk = false;
- if (host->version >= SDHCI_SPEC_300) {
- if (host->preset_enabled) {
- u16 pre_val;
+ if (clock == 0)
+ return clk;
+
+ if (host->preset_enabled) {
+ /* Only version 3.00+ can have preset_enabled */
+ u16 pre_val;
+
+ pre_val = sdhci_get_preset_value(host);
+ div = FIELD_GET(SDHCI_PRESET_SDCLK_FREQ_MASK, pre_val);
+ if (!(pre_val & SDHCI_PRESET_CLKGEN_SEL))
+ goto base_div_set;
+
+ clk = SDHCI_PROG_CLOCK_MODE;
+ real_div = div + 1;
+ clk_mul = host->clk_mul;
+ if (!clk_mul) {
+ /* The clock frequency is unknown. Assume undivided base. */
+ clk_mul = 1;
+ }
+
+ goto clock_set;
+ }
+
+ /*
+ * Check if the Host Controller supports Programmable Clock
+ * Mode.
+ */
+ if (host->version >= SDHCI_SPEC_300 && host->clk_mul) {
+ 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.
+ */
+ clk = SDHCI_PROG_CLOCK_MODE;
+ clk_mul = host->clk_mul;
+ real_div = div--;
- pre_val = sdhci_get_preset_value(host);
- div = FIELD_GET(SDHCI_PRESET_SDCLK_FREQ_MASK, pre_val);
- if (pre_val & SDHCI_PRESET_CLKGEN_SEL) {
- clk = SDHCI_PROG_CLOCK_MODE;
- real_div = div + 1;
- clk_mul = host->clk_mul;
- if (!clk_mul) {
- /* The clock frequency is unknown. Assume undivided base. */
- clk_mul = 1;
- }
- } else {
- real_div = max_t(int, 1, div << 1);
- }
goto clock_set;
}
/*
- * Check if the Host Controller supports Programmable Clock
- * Mode.
+ * Divisor is too big for requested clock rate.
+ * Fall back to the base clock.
*/
- 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) {
- /*
- * Set Programmable Clock Mode in the Clock
- * Control register.
- */
- clk = SDHCI_PROG_CLOCK_MODE;
- real_div = div;
- clk_mul = host->clk_mul;
- div--;
- } else {
- /*
- * Divisor can be too small to reach clock
- * speed requirement. Then use the base clock.
- */
- switch_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;
- }
- }
- real_div = div;
- div >>= 1;
- }
+ div = DIV_ROUND_UP(host->max_clk, clock);
+
+ if (div == 1 && (host->quirks2 & SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN))
+ div = 2;
+
+ if (host->version >= SDHCI_SPEC_300) {
+ /* Version 3.00 divisors must be a multiple of 2. */
+ div = min(div, SDHCI_MAX_DIV_SPEC_300);
+ div = DIV_ROUND_UP(div, 2);
} 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;
- }
- real_div = div;
- div >>= 1;
+ div = min(div, SDHCI_MAX_DIV_SPEC_200);
+ div = roundup_pow_of_two(div) / 2;
}
+base_div_set:
+ real_div = div * 2 + !div;
+
clock_set:
- if (real_div)
- *actual_clock = (host->max_clk * clk_mul) / real_div;
+ *actual_clock = (host->max_clk * clk_mul) / real_div;
clk |= (div & SDHCI_DIV_MASK) << SDHCI_DIVIDER_SHIFT;
clk |= ((div & SDHCI_DIV_HI_MASK) >> SDHCI_DIV_MASK_LEN)
<< SDHCI_DIVIDER_HI_SHIFT;
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 074dc182b184..a3fa70d91410 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -284,8 +284,8 @@
* 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.
--
2.30.2
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