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authorBenjamin Herrenschmidt <benh@au1.ibm.com>2018-05-17 18:12:02 +1000
committerLinus Walleij <linus.walleij@linaro.org>2018-05-23 13:59:06 +0200
commited5cab43f99d1629af0e34ff565aa14efe0a8ac9 (patch)
tree5b38657238a6b4209fa7eeefe60404f325807e15 /drivers/gpio
parentaf7949284910a1f0b7814625051b8acf99af74d2 (diff)
downloadop-kernel-dev-ed5cab43f99d1629af0e34ff565aa14efe0a8ac9.zip
op-kernel-dev-ed5cab43f99d1629af0e34ff565aa14efe0a8ac9.tar.gz
gpio: aspeed: Use a cache of output data registers
The current driver does a read/modify/write of the output registers when changing a bit in __aspeed_gpio_set(). This is sub-optimal for a couple of reasons: - If any of the neighbouring GPIOs (sharing the shared register) isn't (yet) configured as an output, it will read the current input value, and then apply it to the output latch, which may not be what the user expects. There should be no bug in practice as aspeed_gpio_dir_out() will establish a new value but it's not great either. - The GPIO block in the aspeed chip is clocked rather slowly (typically 25Mhz). That extra MMIO read halves the maximum speed at which we can toggle the GPIO. This provides a significant performance improvement to the GPIO based FSI master. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Reviewed-by: Christopher Bostic <cbostic@linux.vnet.ibm.com> Reviewed-by: Andrew Jeffery <andrew@aj.id.au> Tested-by: Joel Stanley <joel@jms.id.au> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'drivers/gpio')
-rw-r--r--drivers/gpio/gpio-aspeed.c21
1 files changed, 19 insertions, 2 deletions
diff --git a/drivers/gpio/gpio-aspeed.c b/drivers/gpio/gpio-aspeed.c
index f210bed..f579bec 100644
--- a/drivers/gpio/gpio-aspeed.c
+++ b/drivers/gpio/gpio-aspeed.c
@@ -54,6 +54,8 @@ struct aspeed_gpio {
u8 *offset_timer;
unsigned int timer_users[4];
struct clk *clk;
+
+ u32 *dcache;
};
struct aspeed_gpio_bank {
@@ -231,12 +233,13 @@ static void __aspeed_gpio_set(struct gpio_chip *gc, unsigned int offset,
u32 reg;
addr = bank_val_reg(gpio, bank, GPIO_DATA);
- reg = ioread32(addr);
+ reg = gpio->dcache[GPIO_BANK(offset)];
if (val)
reg |= GPIO_BIT(offset);
else
reg &= ~GPIO_BIT(offset);
+ gpio->dcache[GPIO_BANK(offset)] = reg;
iowrite32(reg, addr);
}
@@ -851,7 +854,7 @@ static int __init aspeed_gpio_probe(struct platform_device *pdev)
const struct of_device_id *gpio_id;
struct aspeed_gpio *gpio;
struct resource *res;
- int rc;
+ int rc, i, banks;
gpio = devm_kzalloc(&pdev->dev, sizeof(*gpio), GFP_KERNEL);
if (!gpio)
@@ -892,6 +895,20 @@ static int __init aspeed_gpio_probe(struct platform_device *pdev)
gpio->chip.base = -1;
gpio->chip.irq.need_valid_mask = true;
+ /* Allocate a cache of the output registers */
+ banks = gpio->config->nr_gpios >> 5;
+ gpio->dcache = devm_kzalloc(&pdev->dev,
+ sizeof(u32) * banks, GFP_KERNEL);
+ if (!gpio->dcache)
+ return -ENOMEM;
+
+ /* Populate it with initial values read from the HW */
+ for (i = 0; i < banks; i++) {
+ const struct aspeed_gpio_bank *bank = &aspeed_gpio_banks[i];
+ gpio->dcache[i] = ioread32(gpio->base + bank->val_regs +
+ GPIO_DATA);
+ }
+
rc = devm_gpiochip_add_data(&pdev->dev, &gpio->chip, gpio);
if (rc < 0)
return rc;
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