Messages in this thread | | | From | Colin Foster <> | Subject | [RFC v1 0/2] Add more detailed regmap formatting capabilities | Date | Sun, 13 Mar 2022 15:45:22 -0700 |
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The Ocelot chips (specifically the VSC7512 I'm using) have a method of accessing their registers internally via MMIO, or externally via SPI. When accessing these registers externally, a 24-bit address is used and downshifted by two. The manual references it as:
SI_ADDR = (REG_ADDR & 0x00FFFFFF) >> 2;
By adding this configurable downshift, and a configurable register base address, the regmap definitions can be shared between MMIO and SPI configurations.
This also allows regmap to be used in a bus configuration. My initial testing shows that even at a much slower bus speed of 500KHz, I'm seeing an improvement of 10ms (was 14... now 4) to perform bulk read operations.
The relevant MMIO code can be found in drivers/net/mscc/ocelot_io.c:
static struct regmap_config ocelot_regmap_config = { .reg_bits = 32, .val_bits = 32, .reg_stride = 4, };
struct regmap *ocelot_regmap_init(struct ocelot *ocelot, struct resource *res) { void __iomem *regs;
regs = devm_ioremap_resource(ocelot->dev, res); if (IS_ERR(regs)) return ERR_CAST(regs);
ocelot_regmap_config.name = res->name;
return devm_regmap_init_mmio(ocelot->dev, regs, &ocelot_regmap_config); }
And the SPI counterpart is slightly more complex:
static const struct regmap_config ocelot_spi_regmap_config = { .reg_bits = 24, .reg_stride = 4, .reg_downshift = 2, .val_bits = 32,
.write_flag_mask = 0x80,
.max_register = 0xffffffff, .use_single_write = true, .can_multi_write = false,
.reg_format_endian = REGMAP_ENDIAN_BIG, .val_format_endian = REGMAP_ENDIAN_NATIVE, };
static const struct regmap_bus ocelot_spi_regmap_bus = { .write = ocelot_spi_regmap_bus_write, .read = ocelot_spi_regmap_bus_read, };
struct regmap * ocelot_spi_devm_get_regmap(struct ocelot_core *core, struct device *child, const struct resource *res) { struct regmap_config regmap_config;
memcpy(®map_config, &ocelot_spi_regmap_config, sizeof(ocelot_spi_regmap_config));
regmap_config.name = res->name; regmap_config.max_register = res->end - res->start; regmap_config.reg_base = res->start;
return devm_regmap_init(child, &ocelot_spi_regmap_bus, core, ®map_config); }
If there's anything I missed, or if there's a different way to go about this, please let me know. I can also drag this along with my VSC7512 development or I can send this patch (or whatever it might become) after the merge window.
Colin Foster (2): regmap: add configurable downshift for addresses regmap: allow a defined reg_base to be added to every address
drivers/base/regmap/internal.h | 2 ++ drivers/base/regmap/regmap.c | 11 +++++++++++ include/linux/regmap.h | 6 ++++++ 3 files changed, 19 insertions(+)
-- 2.25.1
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