[PATCH linux dev-4.7 v1 1/1] pinctrl: aspeed: Enable ASPEED pinctrl driver to modify SPI1 strap bits

[Kun Yi]

Current pinctrl driver treats HWSTRAP1/HWSTRAP2 bits as read-only. Changing
SPI1 mode requires pinctrl to modify bit 12 and 13 of HWSTRAP1, and keep
other strap bits as read-only.

Note: with this change devicetree default pinctrl settings for spi1 will
effectively override any previous mode set by physical strapping or
aspeed.c when Aspeed smc driver is probed.

Signed-off-by: Kun Yi <kunyi at google.com>
---
 drivers/pinctrl/aspeed/pinctrl-aspeed.c | 22 ++++++++++++++++++++--
 drivers/pinctrl/aspeed/pinctrl-aspeed.h |  2 +-
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/pinctrl/aspeed/pinctrl-aspeed.c b/drivers/pinctrl/aspeed/pinctrl-aspeed.c
index 21ef195..c647503 100644
--- a/drivers/pinctrl/aspeed/pinctrl-aspeed.c
+++ b/drivers/pinctrl/aspeed/pinctrl-aspeed.c
@@ -16,6 +16,8 @@
 
 const char *const aspeed_pinmux_ips[] = { "SCU", "SIO", "GFX", "LPC" };
 
+#define SPI1_REG_MASK   0x3000
+
 int aspeed_pinctrl_get_groups_count(struct pinctrl_dev *pctldev)
 {
 	struct aspeed_pinctrl_data *pdata = pinctrl_dev_get_drvdata(pctldev);
@@ -178,6 +180,7 @@ static bool aspeed_sig_expr_eval(const struct aspeed_sig_expr *expr,
  *
  * @return true if the expression is configured as requested, false otherwise
  */
+
 static bool aspeed_sig_expr_set(const struct aspeed_sig_expr *expr,
 				bool enable, struct regmap *map)
 {
@@ -197,15 +200,30 @@ static bool aspeed_sig_expr_set(const struct aspeed_sig_expr *expr,
 
 		/*
 		 * Strap registers are configured in hardware or by early-boot
-		 * firmware. Treat them as read-only despite that we can write
+		 * firmware. With the exception of SPI1 interface bits, treat
+		 * them as read-only despite that we can write
 		 * them. This may mean that certain functions cannot be
 		 * deconfigured and is the reason we re-evaluate after writing
 		 * all descriptor bits.
 		 */
-		if (is_scu && (offset == HW_STRAP1 || offset == HW_STRAP2))
+		if (is_scu && (offset == HW_STRAP2 ||
+			offset == HW_STRAP1 && desc->mask != SPI1_REG_MASK))
 			continue;
 
 		/*
+		 * HW_STRAP1 bits can only be set to 0 by writing 1 into
+		 * bits of same offset in SCU7C. To configure different SPI1
+		 * modes, we write 1 to SCU7C[13:12] to clear SPI1 mask to make
+		 * sure later write to strap register can take effect.
+		 */
+		if (is_scu && offset == HW_STRAP1 &&
+		    desc->mask == SPI1_REG_MASK) {
+			ret = regmap_write(map, HW_STRAP1_RESET, desc->mask);
+			if (ret)
+				return false;
+		};
+
+		/*
 		 * Sometimes we need help from IP outside the SCU to activate a
 		 * mux request. Report that we need its cooperation.
 		 */
diff --git a/drivers/pinctrl/aspeed/pinctrl-aspeed.h b/drivers/pinctrl/aspeed/pinctrl-aspeed.h
index 68315a8..46ba16d 100644
--- a/drivers/pinctrl/aspeed/pinctrl-aspeed.h
+++ b/drivers/pinctrl/aspeed/pinctrl-aspeed.h
@@ -268,6 +268,7 @@
 #define HW_STRAP2       0xD0 /* Strapping */
 
 #define SIORD30		SIG_DESC_TO_REG(ASPEED_IP_SIO, 0x30)
+#define HW_STRAP1_RESET	SIG_DESC_TO_REG(ASPEED_IP_SCU, 0x7C)
 
  /**
   * A signal descriptor, which describes the register, bits and the
@@ -580,5 +581,4 @@ int aspeed_gpio_request_enable(struct pinctrl_dev *pctldev,
 int aspeed_pinctrl_probe(struct platform_device *pdev,
 		struct pinctrl_desc *pdesc,
 		struct aspeed_pinctrl_data *pdata);
-
 #endif /* PINCTRL_ASPEED */
-- 
2.8.0.rc3.226.g39d4020