diff options
Diffstat (limited to 'drivers/pinctrl/aspeed')
| -rw-r--r-- | drivers/pinctrl/aspeed/pinmux-aspeed.h | 204 |
1 files changed, 200 insertions, 4 deletions
diff --git a/drivers/pinctrl/aspeed/pinmux-aspeed.h b/drivers/pinctrl/aspeed/pinmux-aspeed.h index a036ce8f1571..329d54d48667 100644 --- a/drivers/pinctrl/aspeed/pinmux-aspeed.h +++ b/drivers/pinctrl/aspeed/pinmux-aspeed.h @@ -18,7 +18,8 @@ * priority level are frequently not the same (i.e. cannot just flip a bit to * change from a high to low priority signal), or even in the same register. * Further, not all signals can be unmuxed, as some expressions depend on - * values in the hardware strapping register (which is treated as read-only). + * values in the hardware strapping register (which may be treated as + * read-only). * * SoC Multi-function Pin Expression Examples * ------------------------------------------ @@ -172,9 +173,9 @@ * * A signal expression is the smallest set of signal descriptors whose * comparisons must evaluate 'true' for a signal to be enabled on a pin. * - * * A function's signal is active on a pin if evaluating all signal - * descriptors in the pin's signal expression for the function yields a 'true' - * result + * * A signal participating in a function is active on a pin if evaluating all + * signal descriptors in the pin's signal expression for the function yields + * a 'true' result * * * A signal at a given priority on a given pin is active if any of the * functions in which the signal participates are active, and no higher @@ -221,6 +222,201 @@ * well as pins) required for the group's configuration will already be in use, * likely in a way that's inconsistent with the requirements of the failed * group. + * + * Implementation + * -------------- + * + * Beyond the documentation below the various structures and helper macros that + * allow the implementation to hang together are defined. The macros are fairly + * dense, so below we walk through some raw examples of the configuration + * tables in an effort to clarify the concepts. + * + * The complexity of configuring the mux combined with the scale of the pins + * and functions was a concern, so the table design along with the macro jungle + * is an attempt to address it. The rough principles of the approach are: + * + * 1. Use a data-driven solution rather than embedding state into code + * 2. Minimise editing to the specifics of the given mux configuration + * 3. Detect as many errors as possible at compile time + * + * Addressing point 3 leads to naming of symbols in terms of the four + * properties associated with a given mux configuration: The pin, the signal, + * the group and the function. In this way copy/paste errors cause duplicate + * symbols to be defined, which prevents successful compilation. Failing to + * properly parent the tables leads to unused symbol warnings, and use of + * designated initialisers and additional warnings ensures that there are + * no override errors in the pin, group and function arrays. + * + * Addressing point 2 drives the development of the macro jungle, as it + * centralises the definition noise at the cost of taking some time to + * understand. + * + * Here's a complete, concrete "pre-processed" example of the table structures + * used to describe the D6 ball from the examples above: + * + * ``` + * static const struct aspeed_sig_desc sig_descs_MAC1LINK_MAC1LINK[] = { + * { + * .ip = ASPEED_IP_SCU, + * .reg = 0x80, + * .mask = BIT(0), + * .enable = 1, + * .disable = 0 + * }, + * }; + * + * static const struct aspeed_sig_expr sig_expr_MAC1LINK_MAC1LINK = { + * .signal = "MAC1LINK", + * .function = "MAC1LINK", + * .ndescs = ARRAY_SIZE(sig_descs_MAC1LINK_MAC1LINK), + * .descs = &(sig_descs_MAC1LINK_MAC1LINK)[0], + * }; + * + * static const struct aspeed_sig_expr *sig_exprs_MAC1LINK_MAC1LINK[] = { + * &sig_expr_MAC1LINK_MAC1LINK, + * NULL, + * }; + * + * static const struct aspeed_sig_desc sig_descs_GPIOA0_GPIOA0[] = { }; + * + * static const struct aspeed_sig_expr sig_expr_GPIOA0_GPIOA0 = { + * .signal = "GPIOA0", + * .function = "GPIOA0", + * .ndescs = ARRAY_SIZE(sig_descs_GPIOA0_GPIOA0), + * .descs = &(sig_descs_GPIOA0_GPIOA0)[0], + * }; + * + * static const struct aspeed_sig_expr *sig_exprs_GPIOA0_GPIOA0[] = { + * &sig_expr_GPIOA0_GPIOA0, + * NULL + * }; + * + * static const struct aspeed_sig_expr **pin_exprs_0[] = { + * sig_exprs_MAC1LINK_MAC1LINK, + * sig_exprs_GPIOA0_GPIOA0, + * NULL + * }; + * + * static const struct aspeed_pin_desc pin_0 = { "0", (&pin_exprs_0[0]) }; + * static const int group_pins_MAC1LINK[] = { 0 }; + * static const char *func_groups_MAC1LINK[] = { "MAC1LINK" }; + * + * static struct pinctrl_pin_desc aspeed_g4_pins[] = { + * [0] = { .number = 0, .name = "D6", .drv_data = &pin_0 }, + * }; + * + * static const struct aspeed_pin_group aspeed_g4_groups[] = { + * { + * .name = "MAC1LINK", + * .pins = &(group_pins_MAC1LINK)[0], + * .npins = ARRAY_SIZE(group_pins_MAC1LINK), + * }, + * }; + * + * static const struct aspeed_pin_function aspeed_g4_functions[] = { + * { + * .name = "MAC1LINK", + * .groups = &func_groups_MAC1LINK[0], + * .ngroups = ARRAY_SIZE(func_groups_MAC1LINK), + * }, + * }; + * ``` + * + * At the end of the day much of the above code is compressed into the + * following two lines: + * + * ``` + * #define D6 0 + * SSSF_PIN_DECL(D6, GPIOA0, MAC1LINK, SIG_DESC_SET(SCU80, 0)); + * ``` + * + * The two examples below show just the differences from the example above. + * + * Ball E18 demonstrates a function, EXTRST, that requires multiple descriptors + * be set for it to be muxed: + * + * ``` + * static const struct aspeed_sig_desc sig_descs_EXTRST_EXTRST[] = { + * { + * .ip = ASPEED_IP_SCU, + * .reg = 0x3C, + * .mask = BIT(3), + * .enable = 1, + * .disable = 0 + * }, + * { + * .ip = ASPEED_IP_SCU, + * .reg = 0x80, + * .mask = BIT(15), + * .enable = 1, + * .disable = 0 + * }, + * { + * .ip = ASPEED_IP_SCU, + * .reg = 0x90, + * .mask = BIT(31), + * .enable = 0, + * .disable = 1 + * }, + * }; + * + * static const struct aspeed_sig_expr sig_expr_EXTRST_EXTRST = { + * .signal = "EXTRST", + * .function = "EXTRST", + * .ndescs = ARRAY_SIZE(sig_descs_EXTRST_EXTRST), + * .descs = &(sig_descs_EXTRST_EXTRST)[0], + * }; + * ... + * ``` + * + * For ball E19, we have multiple functions enabling a single signal, LPCRST#. + * The data structures look like: + * + * static const struct aspeed_sig_desc sig_descs_LPCRST_LPCRST[] = { + * { + * .ip = ASPEED_IP_SCU, + * .reg = 0x80, + * .mask = BIT(12), + * .enable = 1, + * .disable = 0 + * }, + * }; + * + * static const struct aspeed_sig_expr sig_expr_LPCRST_LPCRST = { + * .signal = "LPCRST", + * .function = "LPCRST", + * .ndescs = ARRAY_SIZE(sig_descs_LPCRST_LPCRST), + * .descs = &(sig_descs_LPCRST_LPCRST)[0], + * }; + * + * static const struct aspeed_sig_desc sig_descs_LPCRST_LPCRSTS[] = { + * { + * .ip = ASPEED_IP_SCU, + * .reg = 0x70, + * .mask = BIT(14), + * .enable = 1, + * .disable = 0 + * }, + * }; + * + * static const struct aspeed_sig_expr sig_expr_LPCRST_LPCRSTS = { + * .signal = "LPCRST", + * .function = "LPCRSTS", + * .ndescs = ARRAY_SIZE(sig_descs_LPCRST_LPCRSTS), + * .descs = &(sig_descs_LPCRST_LPCRSTS)[0], + * }; + * + * static const struct aspeed_sig_expr *sig_exprs_LPCRST_LPCRST[] = { + * &sig_expr_LPCRST_LPCRST, + * &sig_expr_LPCRST_LPCRSTS, + * NULL, + * }; + * ... + * ``` + * + * Both expressions listed in the sig_exprs_LPCRST_LPCRST array need to be set + * to disabled for the associated GPIO to be muxed. + * */ #define ASPEED_IP_SCU 0 |