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Subject[PATCH 2/2] mmc: sdhci-of-aspeed: Allow max-frequency limitation of SDCLK
Date
Add a get_max_clock() handler to sdhci-of-aspeed to report f_max as the
maximum clock rate if it is set. This enables artificial limitation of
the bus speed via max-frequency in the devicetree for e.g. the AST2600
evaluation board where I am seeing errors at 200MHz.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
---
drivers/mmc/host/sdhci-of-aspeed.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/sdhci-of-aspeed.c b/drivers/mmc/host/sdhci-of-aspeed.c
index a9175ca85696..5cc00abcd71f 100644
--- a/drivers/mmc/host/sdhci-of-aspeed.c
+++ b/drivers/mmc/host/sdhci-of-aspeed.c
@@ -52,16 +52,24 @@ static void aspeed_sdc_configure_8bit_mode(struct aspeed_sdc *sdc,

static void aspeed_sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
{
+ struct sdhci_pltfm_host *pltfm_host;
+ unsigned long parent;
int div;
u16 clk;

+ pltfm_host = sdhci_priv(host);
+ parent = clk_get_rate(pltfm_host->clk);
+
sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);

if (clock == 0)
goto out;

+ if (WARN_ON(clock > host->max_clk))
+ clock = host->max_clk;
+
for (div = 1; div < 256; div *= 2) {
- if ((host->max_clk / div) <= clock)
+ if ((parent / div) <= clock)
break;
}
div >>= 1;
@@ -74,6 +82,14 @@ static void aspeed_sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
host->clock = clock;
}

+static unsigned int aspeed_sdhci_get_max_clock(struct sdhci_host *host)
+{
+ if (host->mmc->f_max)
+ return host->mmc->f_max;
+
+ return sdhci_pltfm_clk_get_max_clock(host);
+}
+
static void aspeed_sdhci_set_bus_width(struct sdhci_host *host, int width)
{
struct sdhci_pltfm_host *pltfm_priv;
@@ -100,7 +116,7 @@ static void aspeed_sdhci_set_bus_width(struct sdhci_host *host, int width)

static const struct sdhci_ops aspeed_sdhci_ops = {
.set_clock = aspeed_sdhci_set_clock,
- .get_max_clock = sdhci_pltfm_clk_get_max_clock,
+ .get_max_clock = aspeed_sdhci_get_max_clock,
.set_bus_width = aspeed_sdhci_set_bus_width,
.get_timeout_clock = sdhci_pltfm_clk_get_max_clock,
.reset = sdhci_reset,
--
2.20.1
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