serial: sh-sci: Replace hardcoded values in SCxSR_*_CLEAR macros

Add the missing overrun error bit in SCxSR on SCIFA/SCIFB and SCIF on
SH7705/SH7720/SH7721.
Document what the corresponding bit(s) on plain SCIF are used for.
Sort the components of SCIF_DEFAULT_ERROR_MASK by reverse definition
order.

Replace the hardcoded values in the SCxSR_*_CLEAR macros by proper
defines. Use bit masks (negations of sets of bits) to make it more
obvious which bits are being cleared.

Assembler output (on sh) was compared before and after this commit:
  - For the first branch of the big "#if defined(...) || ..." construct,
    the code has changed slightly, as 32-bit bitmasks can be loaded in a
    single instruction, unlike the old large 16-bit constants (the SCxSR
    register is 16 bit, so we don't care about the top 16 bits),
  - For the second branch, the generated code is identical.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sh-sci.h

@@ -50,10 +50,16 @@ enum {
 #define SCI_FER		BIT(4)	/* Framing Error */
 #define SCI_PER		BIT(3)	/* Parity Error */
 #define SCI_TEND	BIT(2)	/* Transmit End */
+#define SCI_RESERVED	0x03	/* All reserved bits */
 
 #define SCI_DEFAULT_ERROR_MASK (SCI_PER | SCI_FER)
 
-/* SCxSR (Serial Status Register) on SCIF, HSCIF */
+#define SCI_RDxF_CLEAR	~(SCI_RESERVED | SCI_RDRF)
+#define SCI_ERROR_CLEAR	~(SCI_RESERVED | SCI_PER | SCI_FER | SCI_ORER)
+#define SCI_TDxE_CLEAR	~(SCI_RESERVED | SCI_TEND | SCI_TDRE)
+#define SCI_BREAK_CLEAR	~(SCI_RESERVED | SCI_PER | SCI_FER | SCI_ORER)
+
+/* SCxSR (Serial Status Register) on SCIF, SCIFA, SCIFB, HSCIF */
 #define SCIF_ER		BIT(7)	/* Receive Error */
 #define SCIF_TEND	BIT(6)	/* Transmission End */
 #define SCIF_TDFE	BIT(5)	/* Transmit FIFO Data Empty */
@@ -62,8 +68,18 @@ enum {
 #define SCIF_PER	BIT(2)	/* Parity Error */
 #define SCIF_RDF	BIT(1)	/* Receive FIFO Data Full */
 #define SCIF_DR		BIT(0)	/* Receive Data Ready */
+/* SCIF only (optional) */
+#define SCIF_PERC	0xf000	/* Number of Parity Errors */
+#define SCIF_FERC	0x0f00	/* Number of Framing Errors */
+/*SCIFA/SCIFB and SCIF on SH7705/SH7720/SH7721 only */
+#define SCIFA_ORER	BIT(9)	/* Overrun Error */
+
+#define SCIF_DEFAULT_ERROR_MASK (SCIF_PER | SCIF_FER | SCIF_BRK | SCIF_ER)
 
-#define SCIF_DEFAULT_ERROR_MASK (SCIF_PER | SCIF_FER | SCIF_ER | SCIF_BRK)
+#define SCIF_RDxF_CLEAR		~(SCIF_DR | SCIF_RDF)
+#define SCIF_ERROR_CLEAR	~(SCIFA_ORER | SCIF_PER | SCIF_FER | SCIF_ER)
+#define SCIF_TDxE_CLEAR		~(SCIF_TDFE)
+#define SCIF_BREAK_CLEAR	~(SCIF_PER | SCIF_FER | SCIF_BRK)
 
 /* SCFCR (FIFO Control Register) */
 #define SCFCR_MCE	BIT(3)	/* Modem Control Enable */
@@ -106,14 +122,22 @@ enum {
     defined(CONFIG_ARCH_SH73A0) || \
     defined(CONFIG_ARCH_R8A7740)
 
-# define SCxSR_RDxF_CLEAR(port)	 (serial_port_in(port, SCxSR) & 0xfffc)
-# define SCxSR_ERROR_CLEAR(port) (serial_port_in(port, SCxSR) & 0xfd73)
-# define SCxSR_TDxE_CLEAR(port)	 (serial_port_in(port, SCxSR) & 0xffdf)
-# define SCxSR_BREAK_CLEAR(port) (serial_port_in(port, SCxSR) & 0xffe3)
+# define SCxSR_RDxF_CLEAR(port) \
+	(serial_port_in(port, SCxSR) & SCIF_RDxF_CLEAR)
+# define SCxSR_ERROR_CLEAR(port) \
+	(serial_port_in(port, SCxSR) & SCIF_ERROR_CLEAR)
+# define SCxSR_TDxE_CLEAR(port) \
+	(serial_port_in(port, SCxSR) & SCIF_TDxE_CLEAR)
+# define SCxSR_BREAK_CLEAR(port) \
+	(serial_port_in(port, SCxSR) & SCIF_BREAK_CLEAR)
 #else
-# define SCxSR_RDxF_CLEAR(port)	 (((port)->type == PORT_SCI) ? 0xbc : 0x00fc)
-# define SCxSR_ERROR_CLEAR(port) (((port)->type == PORT_SCI) ? 0xc4 : 0x0073)
-# define SCxSR_TDxE_CLEAR(port)  (((port)->type == PORT_SCI) ? 0x78 : 0x00df)
-# define SCxSR_BREAK_CLEAR(port) (((port)->type == PORT_SCI) ? 0xc4 : 0x00e3)
+# define SCxSR_RDxF_CLEAR(port) \
+	((((port)->type == PORT_SCI) ? SCI_RDxF_CLEAR : SCIF_RDxF_CLEAR) & 0xff)
+# define SCxSR_ERROR_CLEAR(port) \
+	((((port)->type == PORT_SCI) ? SCI_ERROR_CLEAR : SCIF_ERROR_CLEAR) & 0xff)
+# define SCxSR_TDxE_CLEAR(port) \
+	((((port)->type == PORT_SCI) ? SCI_TDxE_CLEAR : SCIF_TDxE_CLEAR) & 0xff)
+# define SCxSR_BREAK_CLEAR(port) \
+	((((port)->type == PORT_SCI) ? SCI_BREAK_CLEAR : SCIF_BREAK_CLEAR) & 0xff)
 #endif