media: rcar-fcp: Add rcar_fcp_soft_reset()

Add a function to perform soft reset of the FCP.

It is intended to support the correct stop procedure of the VSPX-FCPVX
and VSPD-FCPD pairs according to section "62.3.7.3 Reset Operation" of
the R-Car Hardware Manual at revision 1.20.

Signed-off-by: Jacopo Mondi <[e-mail]>
Reviewed-by: Laurent Pinchart <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>

drivers/media/platform/renesas/rcar-fcp.c

···
 
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
···
 
 #include <media/rcar-fcp.h>
 
+#define RCAR_FCP_REG_RST		0x0010
+#define RCAR_FCP_REG_RST_SOFTRST	BIT(0)
+#define RCAR_FCP_REG_STA		0x0018
+#define RCAR_FCP_REG_STA_ACT		BIT(0)
+
 struct rcar_fcp_device {
 	struct list_head list;
 	struct device *dev;
+	void __iomem *base;
 };
 
 static LIST_HEAD(fcp_devices);
 static DEFINE_MUTEX(fcp_lock);
+
+static inline void rcar_fcp_write(struct rcar_fcp_device *fcp, u32 reg, u32 val)
+{
+	iowrite32(val, fcp->base + reg);
+}
 
 /* -----------------------------------------------------------------------------
  * Public API
···
 }
 EXPORT_SYMBOL_GPL(rcar_fcp_disable);
 
+int rcar_fcp_soft_reset(struct rcar_fcp_device *fcp)
+{
+	u32 value;
+	int ret;
+
+	if (!fcp)
+		return 0;
+
+	rcar_fcp_write(fcp, RCAR_FCP_REG_RST, RCAR_FCP_REG_RST_SOFTRST);
+	ret = readl_poll_timeout(fcp->base + RCAR_FCP_REG_STA,
+				 value, !(value & RCAR_FCP_REG_STA_ACT),
+				 1, 100);
+	if (ret)
+		dev_err(fcp->dev, "Failed to soft-reset\n");
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(rcar_fcp_soft_reset);
+
 /* -----------------------------------------------------------------------------
  * Platform Driver
  */
···
 		return -ENOMEM;
 
 	fcp->dev = &pdev->dev;
+
+	fcp->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(fcp->base))
+		return PTR_ERR(fcp->base);
 
 	dma_set_max_seg_size(fcp->dev, UINT_MAX);
 

include/media/rcar-fcp.h

···
 struct device *rcar_fcp_get_device(struct rcar_fcp_device *fcp);
 int rcar_fcp_enable(struct rcar_fcp_device *fcp);
 void rcar_fcp_disable(struct rcar_fcp_device *fcp);
+int rcar_fcp_soft_reset(struct rcar_fcp_device *fcp);
 #else
 static inline struct rcar_fcp_device *rcar_fcp_get(const struct device_node *np)
 {
···
 	return 0;
 }
 static inline void rcar_fcp_disable(struct rcar_fcp_device *fcp) { }
+static inline int rcar_fcp_soft_reset(struct rcar_fcp_device *fcp)
+{
+	return 0;
+}
 #endif
 
 #endif /* __MEDIA_RCAR_FCP_H__ */