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Now IRQ mappings are always created for all (allowed) GPIOs in gpiochip in gpiochip_irqchip_add_key() which goes against the idea of SPARSE_IRQ and, as result, leads to: - increasing of memory consumption for IRQ descriptors most of which will never ever be used (espessially on platform with a high number of GPIOs). (sizeof(struct irq_desc) == 256 on my tested platforms) - imposibility to use GPIO irqchip APIs by gpio drivers when HW implements GPIO IRQ functionality as IRQ crossbar/router which has only limited number of IRQ outputs (example from [1], all GPIOs can be mapped on only 8 IRQs). Hence, remove static IRQ mapping code from gpiochip_irqchip_add_key() and instead replace irq_find_mapping() with irq_create_mapping() in gpiochip_to_irq(). Also add additional gpiochip_irqchip_irq_valid() calls in gpiochip_to_irq() and gpiochip_irq_map(). After this change gpio2irq mapping will happen the following way when GPIO irqchip APIs are used by gpio driver: - IRQ mappings will be created statically if driver passes first_irq>0 vlaue in gpiochip_irqchip_add_key(). - IRQ mappings will be created dynamically from gpio_to_irq() or of_irq_get(). Tested on am335x-evm and dra72-evm-revc. - dra72-evm-revc: number of created irq mappings decreased from 402 -> 135 Mem savings 267*256 = 68352 (66kB) - am335x-evm: number of created irq mappings decreased from 188 -> 63 Mem savings 125*256 = 32000 (31kB) [1] https://lkml.org/lkml/2017/6/15/428 Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.