mmc: sdhci-of-aspeed: Add AST2600 bus clock support
authorAndrew Jeffery <andrew@aj.id.au>
Thu, 14 Jan 2021 03:14:30 +0000 (13:44 +1030)
committerUlf Hansson <ulf.hansson@linaro.org>
Mon, 1 Feb 2021 10:54:47 +0000 (11:54 +0100)
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>
Link: https://lore.kernel.org/r/20210114031433.2388532-4-andrew@aj.id.au
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
drivers/mmc/host/sdhci-of-aspeed.c

index b1a14e7..4b30f6a 100644 (file)
@@ -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, },
        { }
 };