mfd: rtsx: Add clock divider hook

Add callback function conv_clk_and_div_n to convert between SSC clock
and its divider N.
For rtl8411, the formula to calculate SSC clock divider N is different
with the other card reader models.

Signed-off-by: Wei WANG <wei_wang@realsil.com.cn>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/rtl8411.c

@@ -178,6 +178,18 @@ static unsigned int rtl8411_cd_deglitch(struct rtsx_pcr *pcr)
 	return card_exist;
 }
 
+static int rtl8411_conv_clk_and_div_n(int input, int dir)
+{
+	int output;
+
+	if (dir == CLK_TO_DIV_N)
+		output = input * 4 / 5 - 2;
+	else
+		output = (input + 2) * 5 / 4;
+
+	return output;
+}
+
 static const struct pcr_ops rtl8411_pcr_ops = {
 	.extra_init_hw = rtl8411_extra_init_hw,
 	.optimize_phy = NULL,
@@ -189,6 +201,7 @@ static const struct pcr_ops rtl8411_pcr_ops = {
 	.card_power_off = rtl8411_card_power_off,
 	.switch_output_voltage = rtl8411_switch_output_voltage,
 	.cd_deglitch = rtl8411_cd_deglitch,
+	.conv_clk_and_div_n = rtl8411_conv_clk_and_div_n,
 };
 
 /* SD Pull Control Enable:

drivers/mfd/rts5209.c

@@ -174,6 +174,7 @@ static const struct pcr_ops rts5209_pcr_ops = {
 	.card_power_off = rts5209_card_power_off,
 	.switch_output_voltage = rts5209_switch_output_voltage,
 	.cd_deglitch = NULL,
+	.conv_clk_and_div_n = NULL,
 };
 
 /* SD Pull Control Enable:

drivers/mfd/rts5229.c

@@ -144,6 +144,7 @@ static const struct pcr_ops rts5229_pcr_ops = {
 	.card_power_off = rts5229_card_power_off,
 	.switch_output_voltage = rts5229_switch_output_voltage,
 	.cd_deglitch = NULL,
+	.conv_clk_and_div_n = NULL,
 };
 
 /* SD Pull Control Enable:

drivers/mfd/rtsx_pcr.c

@@ -630,6 +630,9 @@ int rtsx_pci_switch_clock(struct rtsx_pcr *pcr, unsigned int card_clock,
 	if (clk == pcr->cur_clock)
 		return 0;
 
+	if (pcr->ops->conv_clk_and_div_n)
+		N = (u8)pcr->ops->conv_clk_and_div_n(clk, CLK_TO_DIV_N);
+	else
 		N = (u8)(clk - 2);
 	if ((clk <= 2) || (N > max_N))
 		return -EINVAL;
@@ -641,7 +644,14 @@ int rtsx_pci_switch_clock(struct rtsx_pcr *pcr, unsigned int card_clock,
 	/* Make sure that the SSC clock div_n is equal or greater than min_N */
 	div = CLK_DIV_1;
 	while ((N < min_N) && (div < max_div)) {
+		if (pcr->ops->conv_clk_and_div_n) {
+			int dbl_clk = pcr->ops->conv_clk_and_div_n(N,
+					DIV_N_TO_CLK) * 2;
+			N = (u8)pcr->ops->conv_clk_and_div_n(dbl_clk,
+					CLK_TO_DIV_N);
+		} else {
 			N = (N + 2) * 2 - 2;
+		}
 		div++;
 	}
 	dev_dbg(&(pcr->pci->dev), "N = %d, div = %d\n", N, div);

include/linux/mfd/rtsx_common.h

@@ -38,6 +38,9 @@
 #define RTSX_SD_CARD			0
 #define RTSX_MS_CARD			1
 
+#define CLK_TO_DIV_N			0
+#define DIV_N_TO_CLK			1
+
 struct platform_device;
 
 struct rtsx_slot {

include/linux/mfd/rtsx_pci.h

@@ -704,6 +704,7 @@ struct pcr_ops {
 	int		(*switch_output_voltage)(struct rtsx_pcr *pcr,
 						u8 voltage);
 	unsigned int	(*cd_deglitch)(struct rtsx_pcr *pcr);
+	int		(*conv_clk_and_div_n)(int clk, int dir);
 };
 
 enum PDEV_STAT  {PDEV_STAT_IDLE, PDEV_STAT_RUN};