Re: [PATCH] i2c: pasemi: Add IRQ support for Apple Silicon
From: Christophe Leroy <hidden>
Date: 2022-08-21 07:24:28
Also in:
linux-arm-kernel, linux-i2c, lkml
Le 20/08/2022 à 21:45, Arminder Singh a écrit :
This is the first time I'm interacting with the Linux mailing lists, so please don't eviscerate me *too much* if I get the formatting wrong. Of course I'm always willing to take criticism and improve my formatting in the future.
The above text should go after you signed-off-by, after the --- , so that it get's ignored by 'git am' when applying.
This patch adds support for IRQs to the PASemi I2C controller driver. This will allow for faster performing I2C transactions on Apple Silicon hardware, as previously, the driver was forced to poll the SMSTA register for a set amount of time. With this patchset the driver on Apple silicon hardware will instead wait for an interrupt which will signal the completion of the I2C transaction. The timeout value for this completion will be the same as the current amount of time the I2C driver polls for. This will result in some performance improvement since the driver will be waiting for less time than it does right now on Apple Silicon hardware. The patch right now will only enable IRQs for Apple Silicon I2C chips, and only if it's able to successfully request the IRQ from the kernel. === Testing === This patch has been tested on both the mainline Linux kernel tree and the Asahi branch (https://github.com/AsahiLinux/linux.git) on both an M1 and M2 MacBook Air, and it compiles successfully as both a module and built-in to the kernel itself. The patch in both trees successfully boots to userspace without any hitch. I do not have PASemi hardware on hand unfortunately, so I'm unable to test the impact of this patch on old PASemi hardware. This is also why I've elected to do the IRQ request and enablement on the Apple platform driver and not in the common file, as I'm not sure if PASemi hardware supports IRQs. I also fixed a quick checkpatch warning on line 303. "i ++" is now "i++". Any and all critiques of the patch would be well appreciated.
That as well shouldn't be part of the commit message.
quoted hunk ↗ jump to hunk
Signed-off-by: Arminder Singh <redacted> --- drivers/i2c/busses/i2c-pasemi-core.c | 29 ++++++++++++++++++++---- drivers/i2c/busses/i2c-pasemi-core.h | 5 ++++ drivers/i2c/busses/i2c-pasemi-platform.c | 8 +++++++ 3 files changed, 37 insertions(+), 5 deletions(-)diff --git a/drivers/i2c/busses/i2c-pasemi-core.c b/drivers/i2c/busses/i2c-pasemi-core.c index 9028ffb58cc0..375aa9528233 100644 --- a/drivers/i2c/busses/i2c-pasemi-core.c +++ b/drivers/i2c/busses/i2c-pasemi-core.c@@ -21,6 +21,7 @@ #define REG_MTXFIFO 0x00 #define REG_MRXFIFO 0x04 #define REG_SMSTA 0x14 +#define REG_IMASK 0x18 #define REG_CTL 0x1c #define REG_REV 0x28@@ -80,14 +81,21 @@ static int pasemi_smb_waitready(struct pasemi_smbus *smbus) { int timeout = 10; unsigned int status; + unsigned int bitmask = SMSTA_XEN | SMSTA_MTN;
Used only inside the if (smbus->use_irq), bitmask should be defined only in that scope.
- status = reg_read(smbus, REG_SMSTA);
This should go in the else block.
-
- while (!(status & SMSTA_XEN) && timeout--) {
- msleep(1);
+ if (smbus->use_irq) {
+ reinit_completion(&smbus->irq_completion);
+ reg_write(smbus, REG_IMASK, bitmask);
+ wait_for_completion_timeout(&smbus->irq_completion, msecs_to_jiffies(10));
status = reg_read(smbus, REG_SMSTA);
+ } else {status is uninitialised when entering the while loop.
+ while (!(status & SMSTA_XEN) && timeout--) {
+ msleep(1);
+ status = reg_read(smbus, REG_SMSTA);
+ }
}
+Why a second blank line here ?
quoted hunk ↗ jump to hunk
/* Got NACK? */ if (status & SMSTA_MTN) return -ENXIO;@@ -300,7 +308,7 @@ static int pasemi_smb_xfer(struct i2c_adapter *adapter, case I2C_SMBUS_BLOCK_DATA: case I2C_SMBUS_BLOCK_PROC_CALL: data->block[0] = len; - for (i = 1; i <= len; i ++) { + for (i = 1; i <= len; i++) {
This shouldn't be part of this patch, it is unrelated.
quoted hunk ↗ jump to hunk
rd = RXFIFO_RD(smbus); if (rd & MRXFIFO_EMPTY) { err = -ENODATA;@@ -348,6 +356,8 @@ int pasemi_i2c_common_probe(struct pasemi_smbus *smbus) if (smbus->hw_rev != PASEMI_HW_REV_PCI) smbus->hw_rev = reg_read(smbus, REG_REV); + reg_write(smbus, REG_IMASK, 0); + pasemi_reset(smbus); error = devm_i2c_add_adapter(smbus->dev, &smbus->adapter);@@ -356,3 +366,12 @@ int pasemi_i2c_common_probe(struct pasemi_smbus *smbus) return 0; } + +irqreturn_t pasemi_irq_handler(int irq, void *dev_id) +{ + struct pasemi_smbus *smbus = (struct pasemi_smbus *)dev_id;
dev_id is void*, the cast is not needed.
quoted hunk ↗ jump to hunk
+ + reg_write(smbus, REG_IMASK, 0); + complete(&smbus->irq_completion); + return IRQ_HANDLED; +}diff --git a/drivers/i2c/busses/i2c-pasemi-core.h b/drivers/i2c/busses/i2c-pasemi-core.h index 4655124a37f3..045e4a9a3d13 100644 --- a/drivers/i2c/busses/i2c-pasemi-core.h +++ b/drivers/i2c/busses/i2c-pasemi-core.h@@ -7,6 +7,7 @@ #include <linux/i2c-smbus.h> #include <linux/io.h> #include <linux/kernel.h> +#include <linux/completion.h> #define PASEMI_HW_REV_PCI -1@@ -16,6 +17,10 @@ struct pasemi_smbus { void __iomem *ioaddr; unsigned int clk_div; int hw_rev; + int use_irq; + struct completion irq_completion;
Keep same alignment for member name.
quoted hunk ↗ jump to hunk
}; int pasemi_i2c_common_probe(struct pasemi_smbus *smbus); + +irqreturn_t pasemi_irq_handler(int irq, void *dev_id);diff --git a/drivers/i2c/busses/i2c-pasemi-platform.c b/drivers/i2c/busses/i2c-pasemi-platform.c index 88a54aaf7e3c..ee1c84e7734b 100644 --- a/drivers/i2c/busses/i2c-pasemi-platform.c +++ b/drivers/i2c/busses/i2c-pasemi-platform.c@@ -49,6 +49,7 @@ static int pasemi_platform_i2c_probe(struct platform_device *pdev) struct pasemi_smbus *smbus; u32 frequency; int error; + int irq_num; data = devm_kzalloc(dev, sizeof(struct pasemi_platform_i2c_data), GFP_KERNEL);@@ -82,6 +83,13 @@ static int pasemi_platform_i2c_probe(struct platform_device *pdev) if (error) goto out_clk_disable; + smbus->use_irq = 0; + init_completion(&smbus->irq_completion); + irq_num = platform_get_irq(pdev, 0); + error = request_irq(irq_num, pasemi_irq_handler, 0, "pasemi_apple_i2c", (void *)smbus); + + if (!error) + smbus->use_irq = 1; platform_set_drvdata(pdev, data); return 0; --2.34.1