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Subject[PATCH v5 3/6] mmc: sdhci-of-aspeed: Add AST2600 bus clock support
Date
The AST2600 can achieve HS200 speeds with a change to the bus clock
divisor behaviour. The divisor can also be more accurate with respect
to the requested clock rate, but keep the one-hot behaviour for
backwards compatibility with the AST2400 and AST2500.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
---
drivers/mmc/host/sdhci-of-aspeed.c | 37 ++++++++++++++++++++++++++----
1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/host/sdhci-of-aspeed.c b/drivers/mmc/host/sdhci-of-aspeed.c
index 788ec7728227..0a181b104752 100644
--- a/drivers/mmc/host/sdhci-of-aspeed.c
+++ b/drivers/mmc/host/sdhci-of-aspeed.c
@@ -59,6 +59,7 @@ struct aspeed_sdhci_phase_desc {
};

struct aspeed_sdhci_pdata {
+ unsigned int clk_div_start;
const struct aspeed_sdhci_phase_desc *phase_desc;
size_t nr_phase_descs;
};
@@ -200,10 +201,13 @@ static void aspeed_sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
{
struct sdhci_pltfm_host *pltfm_host;
unsigned long parent, bus;
+ struct aspeed_sdhci *sdhci;
int div;
u16 clk;

pltfm_host = sdhci_priv(host);
+ sdhci = sdhci_pltfm_priv(pltfm_host);
+
parent = clk_get_rate(pltfm_host->clk);

sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
@@ -214,7 +218,23 @@ static void aspeed_sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
if (WARN_ON(clock > host->max_clk))
clock = host->max_clk;

- for (div = 2; div < 256; div *= 2) {
+ /*
+ * Regarding the AST2600:
+ *
+ * If (EMMC12C[7:6], EMMC12C[15:8] == 0) then
+ * period of SDCLK = period of SDMCLK.
+ *
+ * If (EMMC12C[7:6], EMMC12C[15:8] != 0) then
+ * period of SDCLK = period of SDMCLK * 2 * (EMMC12C[7:6], EMMC[15:8])
+ *
+ * If you keep EMMC12C[7:6] = 0 and EMMC12C[15:8] as one-hot,
+ * 0x1/0x2/0x4/etc, you will find it is compatible to AST2400 or AST2500
+ *
+ * Keep the one-hot behaviour for backwards compatibility except for
+ * supporting the value 0 in (EMMC12C[7:6], EMMC12C[15:8]), and capture
+ * the 0-value capability in clk_div_start.
+ */
+ for (div = sdhci->pdata->clk_div_start; div < 256; div *= 2) {
bus = parent / div;
if (bus <= clock)
break;
@@ -316,6 +336,10 @@ static int aspeed_sdhci_probe(struct platform_device *pdev)
int ret;

aspeed_pdata = of_device_get_match_data(&pdev->dev);
+ if (!aspeed_pdata) {
+ dev_err(&pdev->dev, "Missing platform configuration data\n");
+ return -EINVAL;
+ }

host = sdhci_pltfm_init(pdev, &aspeed_sdhci_pdata, sizeof(*dev));
if (IS_ERR(host))
@@ -334,7 +358,7 @@ static int aspeed_sdhci_probe(struct platform_device *pdev)
else if (slot >= 2)
return -EINVAL;

- if (dev->pdata && slot < dev->pdata->nr_phase_descs) {
+ if (slot < dev->pdata->nr_phase_descs) {
dev->phase_desc = &dev->pdata->phase_desc[slot];
} else {
dev_info(&pdev->dev,
@@ -396,6 +420,10 @@ static int aspeed_sdhci_remove(struct platform_device *pdev)
return 0;
}

+static const struct aspeed_sdhci_pdata ast2400_sdhci_pdata = {
+ .clk_div_start = 2,
+};
+
static const struct aspeed_sdhci_phase_desc ast2600_sdhci_phase[] = {
/* SDHCI/Slot 0 */
[0] = {
@@ -426,13 +454,14 @@ static const struct aspeed_sdhci_phase_desc ast2600_sdhci_phase[] = {
};

static const struct aspeed_sdhci_pdata ast2600_sdhci_pdata = {
+ .clk_div_start = 1,
.phase_desc = ast2600_sdhci_phase,
.nr_phase_descs = ARRAY_SIZE(ast2600_sdhci_phase),
};

static const struct of_device_id aspeed_sdhci_of_match[] = {
- { .compatible = "aspeed,ast2400-sdhci", },
- { .compatible = "aspeed,ast2500-sdhci", },
+ { .compatible = "aspeed,ast2400-sdhci", .data = &ast2400_sdhci_pdata, },
+ { .compatible = "aspeed,ast2500-sdhci", .data = &ast2400_sdhci_pdata, },
{ .compatible = "aspeed,ast2600-sdhci", .data = &ast2600_sdhci_pdata, },
{ }
};
--
2.27.0
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