Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755053Ab2JTKWv (ORCPT ); Sat, 20 Oct 2012 06:22:51 -0400 Received: from mail.work-microwave.de ([62.245.205.51]:45610 "EHLO work-microwave.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754771Ab2JTKWY (ORCPT ); Sat, 20 Oct 2012 06:22:24 -0400 From: Roland Stigge To: gregkh@linuxfoundation.org, grant.likely@secretlab.ca, linus.walleij@linaro.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, w.sang@pengutronix.de, jbe@pengutronix.de, plagnioj@jcrosoft.com, highguy@gmail.com, broonie@opensource.wolfsonmicro.com, daniel-gl@gmx.net, rmallon@gmail.com Cc: Roland Stigge Subject: [PATCH 1/5 v6] gpio: Add a block GPIO API to gpiolib Date: Sat, 20 Oct 2012 12:21:44 +0200 Message-Id: <1350728508-22508-2-git-send-email-stigge@antcom.de> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1350728508-22508-1-git-send-email-stigge@antcom.de> References: <1350728508-22508-1-git-send-email-stigge@antcom.de> X-FEAS-SYSTEM-WL: rst@work-microwave.de, 192.168.11.78 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 13095 Lines: 453 The recurring task of providing simultaneous access to GPIO lines (especially for bit banging protocols) needs an appropriate API. This patch adds a kernel internal "Block GPIO" API that enables simultaneous access to several GPIOs. This is done by abstracting GPIOs to an n-bit word: Once requested, it provides access to a group of GPIOs which can range over multiple GPIO chips. Signed-off-by: Roland Stigge --- Documentation/gpio.txt | 47 +++++++++ drivers/gpio/gpiolib.c | 217 +++++++++++++++++++++++++++++++++++++++++++++ include/asm-generic/gpio.h | 15 +++ include/linux/gpio.h | 74 +++++++++++++++ 4 files changed, 353 insertions(+) --- linux-2.6.orig/Documentation/gpio.txt +++ linux-2.6/Documentation/gpio.txt @@ -439,6 +439,53 @@ slower clock delays the rising edge of S signaling rate accordingly. +Block GPIO +---------- + +The above described interface concentrates on handling single GPIOs. However, +in applications where it is critical to set several GPIOs at once, this +interface doesn't work well, e.g. bit-banging protocols via grouped GPIO lines. +Consider a GPIO controller that is connected via a slow I2C line. When +switching two or more GPIOs one after another, there can be considerable time +between those events. This is solved by an interface called Block GPIO: + +struct gpio_block *gpio_block_create(unsigned int *gpios, size_t size); + +This creates a new block of GPIOs as a list of GPIO numbers with the specified +size which are accessible via the returned struct gpio_block and the accessor +functions described below. Please note that you need to request the GPIOs +separately via gpio_request(). An arbitrary list of globally valid GPIOs can be +specified, even ranging over several gpio_chips. Actual handling of I/O +operations will be done on a best effort base, i.e. simultaneous I/O only where +possible by hardware and implemented in the respective GPIO driver. The number +of GPIOs in one block is limited to the number of bits in an unsigned long, or +BITS_PER_LONG, of the respective platform, i.e. typically at least 32 on a 32 +bit system, and at least 64 on a 64 bit system. However, several blocks can be +defined at once. + +unsigned gpio_block_get(struct gpio_block *block); +void gpio_block_set(struct gpio_block *block, unsigned value); + +With those accessor functions, setting and getting the GPIO values is possible, +analogous to gpio_get_value() and gpio_set_value(). Each bit in the return +value of gpio_block_get() and in the value argument of gpio_block_set() +corresponds to a bit specified on gpio_block_create(). Block operations in +hardware are only possible where the respective GPIO driver implements it, +falling back to using single GPIO operations where the driver only implements +single GPIO access. + +void gpio_block_free(struct gpio_block *block); + +After the GPIO block isn't used anymore, it should be free'd via +gpio_block_free(). + +int gpio_block_register(struct gpio_block *block); +void gpio_block_unregister(struct gpio_block *block); + +These functions can be used to register a GPIO block. Blocks registered this +way will be available via sysfs. + + What do these conventions omit? =============================== One of the biggest things these conventions omit is pin multiplexing, since --- linux-2.6.orig/drivers/gpio/gpiolib.c +++ linux-2.6/drivers/gpio/gpiolib.c @@ -83,6 +83,8 @@ static inline void desc_set_label(struct #endif } +static LIST_HEAD(gpio_block_list); + /* Warn when drivers omit gpio_request() calls -- legal but ill-advised * when setting direction, and otherwise illegal. Until board setup code * and drivers use explicit requests everywhere (which won't happen when @@ -1676,6 +1678,221 @@ void __gpio_set_value(unsigned gpio, int } EXPORT_SYMBOL_GPL(__gpio_set_value); +static int gpio_block_chip_index(struct gpio_block *block, struct gpio_chip *gc) +{ + int i; + + for (i = 0; i < block->nchip; i++) { + if (block->gbc[i].gc == gc) + return i; + } + return -1; +} + +struct gpio_block *gpio_block_create(unsigned *gpios, size_t size, + const char *name) +{ + struct gpio_block *block; + struct gpio_block_chip *gbc; + struct gpio_remap *remap; + void *tmp; + int i; + + if (size < 1 || size > sizeof(unsigned long) * 8) + return ERR_PTR(-EINVAL); + + for (i = 0; i < size; i++) + if (!gpio_is_valid(gpios[i])) + return ERR_PTR(-EINVAL); + + block = kzalloc(sizeof(struct gpio_block), GFP_KERNEL); + if (!block) + return ERR_PTR(-ENOMEM); + + block->name = name; + block->ngpio = size; + block->gpio = kzalloc(sizeof(*block->gpio) * size, GFP_KERNEL); + if (!block->gpio) + goto err1; + + memcpy(block->gpio, gpios, sizeof(*block->gpio) * size); + + for (i = 0; i < size; i++) { + struct gpio_chip *gc = gpio_to_chip(gpios[i]); + int bit = gpios[i] - gc->base; + int index = gpio_block_chip_index(block, gc); + + if (index < 0) { + block->nchip++; + tmp = krealloc(block->gbc, + sizeof(struct gpio_block_chip) * + block->nchip, GFP_KERNEL); + if (!tmp) { + kfree(block->gbc); + goto err2; + } + block->gbc = tmp; + gbc = &block->gbc[block->nchip - 1]; + gbc->gc = gc; + gbc->remap = NULL; + gbc->nremap = 0; + gbc->mask = 0; + } else { + gbc = &block->gbc[index]; + } + /* represents the mask necessary on calls to the driver's + * .get_block() and .set_block() + */ + gbc->mask |= BIT(bit); + + /* collect gpios that are specified together, represented by + * neighboring bits + * + * Note that even though in setting remap is given a negative + * index, the next lines guard that the potential out-of-bounds + * pointer is not dereferenced when out of bounds. + */ + remap = &gbc->remap[gbc->nremap - 1]; + if (!gbc->nremap || (bit - i != remap->offset)) { + gbc->nremap++; + tmp = krealloc(gbc->remap, + sizeof(struct gpio_remap) * + gbc->nremap, GFP_KERNEL); + if (!tmp) { + kfree(gbc->remap); + goto err3; + } + gbc->remap = tmp; + remap = &gbc->remap[gbc->nremap - 1]; + remap->offset = bit - i; + remap->mask = 0; + } + + /* represents the mask necessary for bit reordering between + * gpio_block (i.e. as specified on gpio_block_get() and + * gpio_block_set()) and gpio_chip domain (i.e. as specified on + * the driver's .set_block() and .get_block()) + */ + remap->mask |= BIT(i); + } + + return block; +err3: + for (i = 0; i < block->nchip - 1; i++) + kfree(block->gbc[i].remap); + kfree(block->gbc); +err2: + kfree(block->gpio); +err1: + kfree(block); + return ERR_PTR(-ENOMEM); +} +EXPORT_SYMBOL_GPL(gpio_block_create); + +void gpio_block_free(struct gpio_block *block) +{ + int i; + + for (i = 0; i < block->nchip; i++) + kfree(block->gbc[i].remap); + kfree(block->gpio); + kfree(block->gbc); + kfree(block); +} +EXPORT_SYMBOL_GPL(gpio_block_free); + +unsigned long gpio_block_get(const struct gpio_block *block) +{ + struct gpio_block_chip *gbc; + int i, j; + unsigned long values = 0; + + for (i = 0; i < block->nchip; i++) { + unsigned long remapped = 0; + + gbc = &block->gbc[i]; + + if (gbc->gc->get_block) { + remapped = gbc->gc->get_block(gbc->gc, gbc->mask); + } else { + /* emulate */ + for_each_set_bit(j, &gbc->mask, BITS_PER_LONG) + remapped |= gbc->gc->get(gbc->gc, + gbc->gc->base + j) << j; + } + + for (j = 0; j < gbc->nremap; j++) { + struct gpio_remap *gr = &gbc->remap[j]; + + values |= (remapped >> gr->offset) & gr->mask; + } + } + + return values; +} +EXPORT_SYMBOL_GPL(gpio_block_get); + +void gpio_block_set(struct gpio_block *block, unsigned long values) +{ + struct gpio_block_chip *gbc; + int i, j; + + for (i = 0; i < block->nchip; i++) { + unsigned long remapped = 0; + + gbc = &block->gbc[i]; + + for (j = 0; j < gbc->nremap; j++) { + struct gpio_remap *gr = &gbc->remap[j]; + + remapped |= (values & gr->mask) << gr->offset; + } + if (gbc->gc->set_block) { + gbc->gc->set_block(gbc->gc, gbc->mask, remapped); + } else { + /* emulate */ + for_each_set_bit(j, &gbc->mask, BITS_PER_LONG) + gbc->gc->set(gbc->gc, gbc->gc->base + j, + (remapped >> j) & 1); + } + } +} +EXPORT_SYMBOL_GPL(gpio_block_set); + +struct gpio_block *gpio_block_find_by_name(const char *name) +{ + struct gpio_block *i; + + list_for_each_entry(i, &gpio_block_list, list) + if (!strcmp(i->name, name)) + return i; + return NULL; +} +EXPORT_SYMBOL_GPL(gpio_block_find_by_name); + +int gpio_block_register(struct gpio_block *block) +{ + if (gpio_block_find_by_name(block->name)) + return -EBUSY; + + list_add(&block->list, &gpio_block_list); + + return 0; +} +EXPORT_SYMBOL_GPL(gpio_block_register); + +void gpio_block_unregister(struct gpio_block *block) +{ + struct gpio_block *i; + + list_for_each_entry(i, &gpio_block_list, list) + if (i == block) { + list_del(&i->list); + break; + } +} +EXPORT_SYMBOL_GPL(gpio_block_unregister); + /** * __gpio_cansleep() - report whether gpio value access will sleep * @gpio: gpio in question --- linux-2.6.orig/include/asm-generic/gpio.h +++ linux-2.6/include/asm-generic/gpio.h @@ -43,6 +43,7 @@ static inline bool gpio_is_valid(int num struct device; struct gpio; +struct gpio_block; struct seq_file; struct module; struct device_node; @@ -105,6 +106,8 @@ struct gpio_chip { unsigned offset); int (*get)(struct gpio_chip *chip, unsigned offset); + unsigned long (*get_block)(struct gpio_chip *chip, + unsigned long mask); int (*direction_output)(struct gpio_chip *chip, unsigned offset, int value); int (*set_debounce)(struct gpio_chip *chip, @@ -112,6 +115,9 @@ struct gpio_chip { void (*set)(struct gpio_chip *chip, unsigned offset, int value); + void (*set_block)(struct gpio_chip *chip, + unsigned long mask, + unsigned long values); int (*to_irq)(struct gpio_chip *chip, unsigned offset); @@ -171,6 +177,15 @@ extern void gpio_set_value_cansleep(unsi extern int __gpio_get_value(unsigned gpio); extern void __gpio_set_value(unsigned gpio, int value); +extern struct gpio_block *gpio_block_create(unsigned *gpio, size_t size, + const char *name); +extern void gpio_block_free(struct gpio_block *block); +extern unsigned long gpio_block_get(const struct gpio_block *block); +extern void gpio_block_set(struct gpio_block *block, unsigned long values); +extern struct gpio_block *gpio_block_find_by_name(const char *name); +extern int gpio_block_register(struct gpio_block *block); +extern void gpio_block_unregister(struct gpio_block *block); + extern int __gpio_cansleep(unsigned gpio); extern int __gpio_to_irq(unsigned gpio); --- linux-2.6.orig/include/linux/gpio.h +++ linux-2.6/include/linux/gpio.h @@ -2,6 +2,8 @@ #define __LINUX_GPIO_H #include +#include +#include /* see Documentation/gpio.txt */ @@ -39,6 +41,43 @@ struct gpio { const char *label; }; +/* + * struct gpio_remap - a structure for describing a bit mapping + * @mask: a bit mask + * @offset: how many bits to shift to the left (negative: to the right) + * + * When we are mapping bit values from one word to another (here: from GPIO + * block domain to GPIO driver domain) we first mask them out with mask and + * shift them as specified with offset. More complicated mappings are done by + * grouping several of those structs and adding the results together. + */ +struct gpio_remap { + unsigned long mask; + int offset; +}; + +struct gpio_block_chip { + struct gpio_chip *gc; + struct gpio_remap *remap; + int nremap; + unsigned long mask; +}; + +/** + * struct gpio_block - a structure describing a list of GPIOs for simultaneous + * operations + */ +struct gpio_block { + struct gpio_block_chip *gbc; + size_t nchip; + const char *name; + + int ngpio; + unsigned *gpio; + + struct list_head list; +}; + #ifdef CONFIG_GENERIC_GPIO #ifdef CONFIG_ARCH_HAVE_CUSTOM_GPIO_H @@ -169,6 +208,41 @@ static inline void gpio_set_value(unsign WARN_ON(1); } +static inline +struct gpio_block *gpio_block_create(unsigned *gpios, size_t size, + const char *name) +{ + WARN_ON(1); + return NULL; +} + +static inline void gpio_block_free(struct gpio_block *block) +{ + WARN_ON(1); +} + +static inline unsigned long gpio_block_get(const struct gpio_block *block) +{ + WARN_ON(1); + return 0; +} + +static inline void gpio_block_set(struct gpio_block *block, unsigned long value) +{ + WARN_ON(1); +} + +static inline int gpio_block_register(struct gpio_block *block) +{ + WARN_ON(1); + return 0; +} + +static inline void gpio_block_unregister(struct gpio_block *block) +{ + WARN_ON(1); +} + static inline int gpio_cansleep(unsigned gpio) { /* GPIO can never have been requested or set as {in,out}put */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/