From 51f109228308a87c7f2583360e54acfc567203da Mon Sep 17 00:00:00 2001 From: Gabriel Somlo Date: Tue, 12 Jan 2021 12:31:43 -0500 Subject: drivers/soc/litex: support 32-bit subregisters, 64-bit CPUs Upstream LiteX now defaults to using 32-bit CSR subregisters (see https://github.com/enjoy-digital/litex/commit/a2b71fde). This patch expands on commit 22447a99c97e ("drivers/soc/litex: add LiteX SoC Controller driver"), adding support for handling both 8- and 32-bit LiteX CSR (MMIO) subregisters, as determined by the LITEX_SUBREG_SIZE Kconfig option. NOTE that while LITEX_SUBREG_SIZE could theoretically be a device tree property, defining it as a compile-time constant allows for much better optimization of the resulting code. This is further supported by the low expected usefulness of deploying the same kernel across LiteX SoCs built with different CSR-Bus data widths. Finally, the litex_[read|write][8|16|32|64]() accessors are redefined in terms of litex_[get|set]_reg(), which, after compiler optimization, will result in code as efficient as hardcoded shifts, but with the added benefit of automatically matching the appropriate LITEX_SUBREG_SIZE. NOTE that litex_[get|set]_reg() nominally operate on 64-bit data, but that will also be optimized by the compiler in situations where narrower data is used from a call site. Signed-off-by: Gabriel Somlo Signed-off-by: Stafford Horne --- drivers/soc/litex/Kconfig | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'drivers/soc/litex/Kconfig') diff --git a/drivers/soc/litex/Kconfig b/drivers/soc/litex/Kconfig index 7c6b009b6f6c..973f8d2fe1a7 100644 --- a/drivers/soc/litex/Kconfig +++ b/drivers/soc/litex/Kconfig @@ -16,4 +16,16 @@ 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 -- cgit v1.2.3 From 4f70d150294b3ddfbe4be7130ca53898cd5b91be Mon Sep 17 00:00:00 2001 From: Gabriel Somlo Date: Tue, 12 Jan 2021 12:31:44 -0500 Subject: drivers/soc/litex: make 'litex_[set|get]_reg()' methods private The 'litex_[set|get]_reg()' methods use the 'reg_size' parameter to specify the width of the LiteX CSR (MMIO) register being accessed. Since 'u64' is the widest data being supported, the value of 'reg_size' MUST be between 1 and sizeof(u64), which SHOULD be checked at runtime if these methods are publicly available for use by other LiteX device drivers. At the same time, none of the existing (or foreseeable) LiteX device drivers have a need to access registers whose size is unknown during compilation. As such, all LiteX device drivers should use fixed-width accessor methods such as 'litex_[write|read][8|16|32|64]()'. This patch renames 'litex_[set|get]_reg()' to '_litex_[set|get]_reg()', indicating that they should NOT be directly called from outside of the 'include/linux/litex.h' header file. Signed-off-by: Gabriel Somlo Signed-off-by: Stafford Horne --- drivers/soc/litex/Kconfig | 2 +- include/linux/litex.h | 35 ++++++++++++++++++++--------------- 2 files changed, 21 insertions(+), 16 deletions(-) (limited to 'drivers/soc/litex/Kconfig') diff --git a/drivers/soc/litex/Kconfig b/drivers/soc/litex/Kconfig index 973f8d2fe1a7..b9b3d51ea7df 100644 --- a/drivers/soc/litex/Kconfig +++ b/drivers/soc/litex/Kconfig @@ -11,7 +11,7 @@ config LITEX_SOC_CONTROLLER select LITEX help This option enables the SoC Controller Driver which verifies - LiteX CSR access and provides common litex_get_reg/litex_set_reg + LiteX CSR access and provides common litex_[read|write]* accessors. All drivers that use functions from litex.h must depend on LITEX. diff --git a/include/linux/litex.h b/include/linux/litex.h index 3456d527f644..5ea9ccf5cce4 100644 --- a/include/linux/litex.h +++ b/include/linux/litex.h @@ -59,21 +59,25 @@ static inline u32 _read_litex_subregister(void __iomem *addr) ((off) + _litex_num_subregs(size) * LITEX_SUBREG_ALIGN) /* - * The purpose of `litex_set_reg`/`litex_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. + * 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 the value to the LiteX CSR (Control&Status Register) + * _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) +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; @@ -85,7 +89,7 @@ static inline void litex_set_reg(void __iomem *reg, size_t reg_size, u64 val) } /** - * litex_get_reg() - Reads the value of the LiteX CSR (Control&Status Register) + * _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 * @@ -93,8 +97,9 @@ static inline void litex_set_reg(void __iomem *reg, size_t reg_size, u64 val) * * 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) +static inline u64 _litex_get_reg(void __iomem *reg, size_t reg_size) { u64 r; u8 i; @@ -110,42 +115,42 @@ static inline u64 litex_get_reg(void __iomem *reg, size_t reg_size) static inline void litex_write8(void __iomem *reg, u8 val) { - litex_set_reg(reg, sizeof(u8), val); + _litex_set_reg(reg, sizeof(u8), val); } static inline void litex_write16(void __iomem *reg, u16 val) { - litex_set_reg(reg, sizeof(u16), val); + _litex_set_reg(reg, sizeof(u16), val); } static inline void litex_write32(void __iomem *reg, u32 val) { - litex_set_reg(reg, sizeof(u32), val); + _litex_set_reg(reg, sizeof(u32), val); } static inline void litex_write64(void __iomem *reg, u64 val) { - litex_set_reg(reg, sizeof(u64), val); + _litex_set_reg(reg, sizeof(u64), val); } static inline u8 litex_read8(void __iomem *reg) { - return litex_get_reg(reg, sizeof(u8)); + return _litex_get_reg(reg, sizeof(u8)); } static inline u16 litex_read16(void __iomem *reg) { - return litex_get_reg(reg, sizeof(u16)); + return _litex_get_reg(reg, sizeof(u16)); } static inline u32 litex_read32(void __iomem *reg) { - return litex_get_reg(reg, sizeof(u32)); + return _litex_get_reg(reg, sizeof(u32)); } static inline u64 litex_read64(void __iomem *reg) { - return litex_get_reg(reg, sizeof(u64)); + return _litex_get_reg(reg, sizeof(u64)); } #endif /* _LINUX_LITEX_H */ -- cgit v1.2.3