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drivers/soc/litex: remove 8-bit subregister option

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Since upstream LiteX recommends that Linux support be limited to
designs configured with 32-bit CSR subregisters (see commit a2b71fde
in upstream LiteX, https://github.com/enjoy-digital/litex), remove
the option to select 8-bit subregisters, significantly reducing the
complexity of LiteX CSR (MMIO register) accessor methods.

NOTE: for details on the underlying mechanics of LiteX CSR registers,
see https://github.com/enjoy-digital/litex/wiki/CSR-Bus or the original
LiteX accessors (litex/soc/software/include/hw/common.h in the upstream
repository).

Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Florent Kermarrec <florent@enjoy-digital.fr>
Cc: Mateusz Holenko <mholenko@antmicro.com>
Cc: Joel Stanley <joel@jms.id.au>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Stafford Horne <shorne@gmail.com>
This commit is contained in:
Gabriel Somlo 2021-05-26 06:51:26 -04:00 committed by Stafford Horne
parent 614124bea7
commit ad4e600cbf
3 changed files with 16 additions and 102 deletions
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12
drivers/soc/litex/Kconfig
View File

@ -17,16 +17,4 @@ config LITEX_SOC_CONTROLLER
All drivers that use functions from litex.h must depend on
LITEX.
config LITEX_SUBREG_SIZE
int "Size of a LiteX CSR subregister, in bytes"
depends on LITEX
range 1 4
default 4
help
LiteX MMIO registers (referred to as Configuration and Status
registers, or CSRs) are spread across adjacent 8- or 32-bit
subregisters, located at 32-bit aligned MMIO addresses. Use
this to select the appropriate size (1 or 4 bytes) matching
your particular LiteX build.
endmenu

3
drivers/soc/litex/litex_soc_ctrl.c
View File

@ -62,8 +62,7 @@ static int litex_check_csr_access(void __iomem *reg_addr)
/* restore original value of the SCRATCH register */
litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_REG_VALUE);
pr_info("LiteX SoC Controller driver initialized: subreg:%d, align:%d",
LITEX_SUBREG_SIZE, LITEX_SUBREG_ALIGN);
pr_info("LiteX SoC Controller driver initialized");
return 0;
}

103
include/linux/litex.h
View File

@ -11,18 +11,6 @@
#include <linux/io.h>
/* LiteX SoCs support 8- or 32-bit CSR Bus data width (i.e., subreg. size) */
#if defined(CONFIG_LITEX_SUBREG_SIZE) && \
(CONFIG_LITEX_SUBREG_SIZE == 1 || CONFIG_LITEX_SUBREG_SIZE == 4)
#define LITEX_SUBREG_SIZE CONFIG_LITEX_SUBREG_SIZE
#else
#error LiteX subregister size (LITEX_SUBREG_SIZE) must be 4 or 1!
#endif
#define LITEX_SUBREG_SIZE_BIT (LITEX_SUBREG_SIZE * 8)
/* LiteX subregisters of any width are always aligned on a 4-byte boundary */
#define LITEX_SUBREG_ALIGN 0x4
static inline void _write_litex_subregister(u32 val, void __iomem *addr)
{
writel((u32 __force)cpu_to_le32(val), addr);
@ -42,115 +30,54 @@ static inline u32 _read_litex_subregister(void __iomem *addr)
* 32-bit wide logical CSR will be laid out as four 32-bit physical
* subregisters, each one containing one byte of meaningful data.
*
* For Linux support, upstream LiteX enforces a 32-bit wide CSR bus, which
* means that only larger-than-32-bit CSRs will be split across multiple
* subregisters (e.g., a 64-bit CSR will be spread across two consecutive
* 32-bit subregisters).
*
* For details see: https://github.com/enjoy-digital/litex/wiki/CSR-Bus
*/
/* number of LiteX subregisters needed to store a register of given reg_size */
#define _litex_num_subregs(reg_size) \
(((reg_size) - 1) / LITEX_SUBREG_SIZE + 1)
/*
* since the number of 4-byte aligned subregisters required to store a single
* LiteX CSR (MMIO) register varies with LITEX_SUBREG_SIZE, the offset of the
* next adjacent LiteX CSR register w.r.t. the offset of the current one also
* depends on how many subregisters the latter is spread across
*/
#define _next_reg_off(off, size) \
((off) + _litex_num_subregs(size) * LITEX_SUBREG_ALIGN)
/*
* The purpose of `_litex_[set|get]_reg()` is to implement the logic of
* writing to/reading from the LiteX CSR in a single place that can be then
* reused by all LiteX drivers via the `litex_[write|read][8|16|32|64]()`
* accessors for the appropriate data width.
* NOTE: direct use of `_litex_[set|get]_reg()` by LiteX drivers is strongly
* discouraged, as they perform no error checking on the requested data width!
*/
/**
* _litex_set_reg() - Writes a value to the LiteX CSR (Control&Status Register)
* @reg: Address of the CSR
* @reg_size: The width of the CSR expressed in the number of bytes
* @val: Value to be written to the CSR
*
* This function splits a single (possibly multi-byte) LiteX CSR write into
* a series of subregister writes with a proper offset.
* NOTE: caller is responsible for ensuring (0 < reg_size <= sizeof(u64)).
*/
static inline void _litex_set_reg(void __iomem *reg, size_t reg_size, u64 val)
{
u8 shift = _litex_num_subregs(reg_size) * LITEX_SUBREG_SIZE_BIT;
while (shift > 0) {
shift -= LITEX_SUBREG_SIZE_BIT;
_write_litex_subregister(val >> shift, reg);
reg += LITEX_SUBREG_ALIGN;
}
}
/**
* _litex_get_reg() - Reads a value of the LiteX CSR (Control&Status Register)
* @reg: Address of the CSR
* @reg_size: The width of the CSR expressed in the number of bytes
*
* Return: Value read from the CSR
*
* This function generates a series of subregister reads with a proper offset
* and joins their results into a single (possibly multi-byte) LiteX CSR value.
* NOTE: caller is responsible for ensuring (0 < reg_size <= sizeof(u64)).
*/
static inline u64 _litex_get_reg(void __iomem *reg, size_t reg_size)
{
u64 r;
u8 i;
r = _read_litex_subregister(reg);
for (i = 1; i < _litex_num_subregs(reg_size); i++) {
r <<= LITEX_SUBREG_SIZE_BIT;
reg += LITEX_SUBREG_ALIGN;
r |= _read_litex_subregister(reg);
}
return r;
}
static inline void litex_write8(void __iomem *reg, u8 val)
{
_litex_set_reg(reg, sizeof(u8), val);
_write_litex_subregister(val, reg);
}
static inline void litex_write16(void __iomem *reg, u16 val)
{
_litex_set_reg(reg, sizeof(u16), val);
_write_litex_subregister(val, reg);
}
static inline void litex_write32(void __iomem *reg, u32 val)
{
_litex_set_reg(reg, sizeof(u32), val);
_write_litex_subregister(val, reg);
}
static inline void litex_write64(void __iomem *reg, u64 val)
{
_litex_set_reg(reg, sizeof(u64), val);
_write_litex_subregister(val >> 32, reg);
_write_litex_subregister(val, reg + 4);
}
static inline u8 litex_read8(void __iomem *reg)
{
return _litex_get_reg(reg, sizeof(u8));
return _read_litex_subregister(reg);
}
static inline u16 litex_read16(void __iomem *reg)
{
return _litex_get_reg(reg, sizeof(u16));
return _read_litex_subregister(reg);
}
static inline u32 litex_read32(void __iomem *reg)
{
return _litex_get_reg(reg, sizeof(u32));
return _read_litex_subregister(reg);
}
static inline u64 litex_read64(void __iomem *reg)
{
return _litex_get_reg(reg, sizeof(u64));
return ((u64)_read_litex_subregister(reg) << 32) |
_read_litex_subregister(reg + 4);
}
#endif /* _LINUX_LITEX_H */