mmc: sdhci-pci-gli: Add a switch to enable/disable SSC for GL9750 and GL9755

Add a vendor-specific bit at the bit26 of GL9750's register 878h and
GL9755's register 78h to decide whether to disable SSC function. If
this bit is set, the SSC function will be disabled.
Signed-off-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
Link: https://lore.kernel.org/r/20220119075406.36321-1-benchuanggli@gmail.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-pci-gli.c

@@ -63,6 +63,7 @@
 #define   GLI_9750_MISC_RX_INV_OFF       0x0
 #define   GLI_9750_MISC_RX_INV_VALUE     GLI_9750_MISC_RX_INV_OFF
 #define   GLI_9750_MISC_TX1_DLY_VALUE    0x5
+#define   SDHCI_GLI_9750_MISC_SSC_OFF    BIT(26)
 
 #define SDHCI_GLI_9750_TUNING_CONTROL	          0x540
 #define   SDHCI_GLI_9750_TUNING_CONTROL_EN          BIT(4)
@@ -137,6 +138,9 @@
 #define PCI_GLI_9755_SerDes  0x70
 #define PCI_GLI_9755_SCP_DIS   BIT(19)
 
+#define PCI_GLI_9755_MISC	    0x78
+#define   PCI_GLI_9755_MISC_SSC_OFF    BIT(26)
+
 #define GLI_MAX_TUNING_LOOP 40
 
 /* Genesys Logic chipset */
@@ -371,6 +375,19 @@ static void gl9750_set_pll(struct sdhci_host *host, u8 dir, u16 ldiv, u8 pdiv)
 	mdelay(1);
 }
 
+static bool gl9750_ssc_enable(struct sdhci_host *host)
+{
+	u32 misc;
+	u8 off;
+
+	gl9750_wt_on(host);
+	misc = sdhci_readl(host, SDHCI_GLI_9750_MISC);
+	off = FIELD_GET(SDHCI_GLI_9750_MISC_SSC_OFF, misc);
+	gl9750_wt_off(host);
+
+	return !off;
+}
+
 static void gl9750_set_ssc(struct sdhci_host *host, u8 enable, u8 step, u16 ppm)
 {
 	u32 pll;
@@ -392,22 +409,28 @@ static void gl9750_set_ssc(struct sdhci_host *host, u8 enable, u8 step, u16 ppm)
 
 static void gl9750_set_ssc_pll_205mhz(struct sdhci_host *host)
 {
-	/* set pll to 205MHz and enable ssc */
-	gl9750_set_ssc(host, 0x1, 0xF, 0x5A1D);
+	bool enable = gl9750_ssc_enable(host);
+
+	/* set pll to 205MHz and ssc */
+	gl9750_set_ssc(host, enable, 0xF, 0x5A1D);
 	gl9750_set_pll(host, 0x1, 0x246, 0x0);
 }
 
 static void gl9750_set_ssc_pll_100mhz(struct sdhci_host *host)
 {
-	/* set pll to 100MHz and enable ssc */
-	gl9750_set_ssc(host, 0x1, 0xE, 0x51EC);
+	bool enable = gl9750_ssc_enable(host);
+
+	/* set pll to 100MHz and ssc */
+	gl9750_set_ssc(host, enable, 0xE, 0x51EC);
 	gl9750_set_pll(host, 0x1, 0x244, 0x1);
 }
 
 static void gl9750_set_ssc_pll_50mhz(struct sdhci_host *host)
 {
-	/* set pll to 50MHz and enable ssc */
-	gl9750_set_ssc(host, 0x1, 0xE, 0x51EC);
+	bool enable = gl9750_ssc_enable(host);
+
+	/* set pll to 50MHz and ssc */
+	gl9750_set_ssc(host, enable, 0xE, 0x51EC);
 	gl9750_set_pll(host, 0x1, 0x244, 0x3);
 }
 
@@ -532,6 +555,19 @@ static void gl9755_set_pll(struct pci_dev *pdev, u8 dir, u16 ldiv, u8 pdiv)
 	mdelay(1);
 }
 
+static bool gl9755_ssc_enable(struct pci_dev *pdev)
+{
+	u32 misc;
+	u8 off;
+
+	gl9755_wt_on(pdev);
+	pci_read_config_dword(pdev, PCI_GLI_9755_MISC, &misc);
+	off = FIELD_GET(PCI_GLI_9755_MISC_SSC_OFF, misc);
+	gl9755_wt_off(pdev);
+
+	return !off;
+}
+
 static void gl9755_set_ssc(struct pci_dev *pdev, u8 enable, u8 step, u16 ppm)
 {
 	u32 pll;
@@ -553,22 +589,28 @@ static void gl9755_set_ssc(struct pci_dev *pdev, u8 enable, u8 step, u16 ppm)
 
 static void gl9755_set_ssc_pll_205mhz(struct pci_dev *pdev)
 {
-	/* set pll to 205MHz and enable ssc */
-	gl9755_set_ssc(pdev, 0x1, 0xF, 0x5A1D);
+	bool enable = gl9755_ssc_enable(pdev);
+
+	/* set pll to 205MHz and ssc */
+	gl9755_set_ssc(pdev, enable, 0xF, 0x5A1D);
 	gl9755_set_pll(pdev, 0x1, 0x246, 0x0);
 }
 
 static void gl9755_set_ssc_pll_100mhz(struct pci_dev *pdev)
 {
-	/* set pll to 100MHz and enable ssc */
-	gl9755_set_ssc(pdev, 0x1, 0xE, 0x51EC);
+	bool enable = gl9755_ssc_enable(pdev);
+
+	/* set pll to 100MHz and ssc */
+	gl9755_set_ssc(pdev, enable, 0xE, 0x51EC);
 	gl9755_set_pll(pdev, 0x1, 0x244, 0x1);
 }
 
 static void gl9755_set_ssc_pll_50mhz(struct pci_dev *pdev)
 {
-	/* set pll to 50MHz and enable ssc */
-	gl9755_set_ssc(pdev, 0x1, 0xE, 0x51EC);
+	bool enable = gl9755_ssc_enable(pdev);
+
+	/* set pll to 50MHz and ssc */
+	gl9755_set_ssc(pdev, enable, 0xE, 0x51EC);
 	gl9755_set_pll(pdev, 0x1, 0x244, 0x3);
 }