clk: thead: Fix TH1520 emmc and shdci clock rate

In accordance with LicheePi 4A BSP the clock that comes to emmc/sdhci
is 198Mhz which is got through frequency division of source clock
VIDEO PLL by 4 [1].

But now the AP_SUBSYS driver sets the CLK EMMC SDIO to the same
frequency as the VIDEO PLL, equal to 792 MHz. This causes emmc/sdhci
to work 4 times slower.

Let's fix this issue by adding fixed factor clock that divides
VIDEO PLL by 4 for emmc/sdhci.

Link: https://github.com/revyos/thead-kernel/blob/7563179071a314f41cdcdbfd8cf6e101e73707f3/drivers/clk/thead/clk-light-fm.c#L454

Fixes: ae81b69 ("clk: thead: Add support for T-Head TH1520 AP_SUBSYS clocks")
Signed-off-by: Maksim Kiselev <bigunclemax@gmail.com>
Link: https://lore.kernel.org/r/20241210083029.92620-1-bigunclemax@gmail.com
Tested-by: Xi Ruoyao <xry111@xry111.site>
Reviewed-by: Drew Fustini <dfustini@tenstorrent.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/thead/clk-th1520-ap.c

@@ -779,6 +779,13 @@ static struct ccu_div dpu1_clk = {
 	},
 };
 
+static CLK_FIXED_FACTOR_HW(emmc_sdio_ref_clk, "emmc-sdio-ref",
+			   &video_pll_clk.common.hw, 4, 1, 0);
+
+static const struct clk_parent_data emmc_sdio_ref_clk_pd[] = {
+	{ .hw = &emmc_sdio_ref_clk.hw },
+};
+
 static CCU_GATE(CLK_BROM, brom_clk, "brom", ahb2_cpusys_hclk_pd, 0x100, BIT(4), 0);
 static CCU_GATE(CLK_BMU, bmu_clk, "bmu", axi4_cpusys2_aclk_pd, 0x100, BIT(5), 0);
 static CCU_GATE(CLK_AON2CPU_A2X, aon2cpu_a2x_clk, "aon2cpu-a2x", axi4_cpusys2_aclk_pd,
@@ -798,7 +805,7 @@ static CCU_GATE(CLK_PERISYS_APB4_HCLK, perisys_apb4_hclk, "perisys-apb4-hclk", p
 		0x150, BIT(12), 0);
 static CCU_GATE(CLK_NPU_AXI, npu_axi_clk, "npu-axi", axi_aclk_pd, 0x1c8, BIT(5), 0);
 static CCU_GATE(CLK_CPU2VP, cpu2vp_clk, "cpu2vp", axi_aclk_pd, 0x1e0, BIT(13), 0);
-static CCU_GATE(CLK_EMMC_SDIO, emmc_sdio_clk, "emmc-sdio", video_pll_clk_pd, 0x204, BIT(30), 0);
+static CCU_GATE(CLK_EMMC_SDIO, emmc_sdio_clk, "emmc-sdio", emmc_sdio_ref_clk_pd, 0x204, BIT(30), 0);
 static CCU_GATE(CLK_GMAC1, gmac1_clk, "gmac1", gmac_pll_clk_pd, 0x204, BIT(26), 0);
 static CCU_GATE(CLK_PADCTRL1, padctrl1_clk, "padctrl1", perisys_apb_pclk_pd, 0x204, BIT(24), 0);
 static CCU_GATE(CLK_DSMART, dsmart_clk, "dsmart", perisys_apb_pclk_pd, 0x204, BIT(23), 0);
@@ -1059,6 +1066,10 @@ static int th1520_clk_probe(struct platform_device *pdev)
 		return ret;
 	priv->hws[CLK_PLL_GMAC_100M] = &gmac_pll_clk_100m.hw;
 
+	ret = devm_clk_hw_register(dev, &emmc_sdio_ref_clk.hw);
+	if (ret)
+		return ret;
+
 	ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_onecell_get, priv);
 	if (ret)
 		return ret;