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Message-Id: <A0B81E7F-BF26-424D-B9E5-5647323B24EC@svenpeter.dev>
Date: Sat, 8 Oct 2022 11:48:42 +0200
From: Sven Peter <sven@...npeter.dev>
To: Arminder Singh <arminders208@...look.com>
Cc: linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, asahi@...ts.linux.dev,
linuxppc-dev@...ts.ozlabs.org,
Alyssa Rosenzweig <alyssa@...enzweig.io>,
Hector Martin <marcan@...can.st>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Nicholas Piggin <npiggin@...il.com>,
Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v3] i2c/pasemi: PASemi I2C controller IRQ enablement
Hi,
> On 7. Oct 2022, at 02:43, Arminder Singh <arminders208@...look.com> wrote:
>
> This patch adds IRQ support to the PASemi I2C controller driver to
> increase the performace of I2C transactions on platforms with PASemi I2C
> controllers. While primarily intended for Apple silicon platforms, this
> patch should also help in enabling IRQ support for older PASemi hardware
> as well should the need arise.
>
> Signed-off-by: Arminder Singh <arminders208@...look.com>
> ---
> This version of the patch has been tested on an M1 Ultra Mac Studio,
> as well as an M1 MacBook Pro, and userspace launches successfully
> while using the IRQ path for I2C transactions.
I think Wolfram suggested to keep this in the commit message. If in doubt listen to him and not me because he’s much more experienced with the kernel than I am ;)
>
> This version of the patch only contains fixes to the whitespace and
> alignment issues found in v2 of the patch, and as such the testing that
> Christian Zigotsky did on PASemi hardware for v2 of the patch also applies
> to this version of the patch as well.
> (See v2 patch email thread for the "Tested-by" tag)
You can just collect and keep those tags above your signed off by if you only change things like whitespaces.
>
> v2 to v3 changes:
> - Fixed some whitespace and alignment issues found in v2 of the patch
>
> v1 to v2 changes:
> - moved completion setup from pasemi_platform_i2c_probe to
> pasemi_i2c_common_probe to allow PASemi and Apple platforms to share
> common completion setup code in case PASemi hardware gets IRQ support
> added
> - initialized the status variable in pasemi_smb_waitready when going down
> the non-IRQ path
> - removed an unnecessary cast of dev_id in the IRQ handler
> - fixed alignment of struct member names in i2c-pasemi-core.h
> (addresses Christophe's feedback in the original submission)
> - IRQs are now disabled after the wait_for_completion_timeout call
> instead of inside the IRQ handler
> (prevents the IRQ from going off after the completion times out)
> - changed the request_irq call to a devm_request_irq call to obviate
> the need for a remove function and a free_irq call
> (thanks to Sven for pointing this out in the original submission)
> - added a reinit_completion call to pasemi_reset
> as a failsafe to prevent missed interrupts from causing the completion
> to never complete (thanks to Arnd Bergmann for pointing this out)
> - removed the bitmask variable in favor of just using the value
> directly (it wasn't used anywhere else)
>
> v2 linked here: https://lore.kernel.org/linux-i2c/MN2PR01MB535821C8058C7814B2F8EEDF9F599@MN2PR01MB5358.prod.exchangelabs.com/
> v1 linked here: https://lore.kernel.org/linux-i2c/MN2PR01MB535838492432C910F2381F929F6F9@MN2PR01MB5358.prod.exchangelabs.com/T/#m11b3504c2667517aad7521514c99ca0e07a9381f
>
> Hopefully the patch is good to go this time around!
>
> drivers/i2c/busses/i2c-pasemi-core.c | 29 ++++++++++++++++++++----
> drivers/i2c/busses/i2c-pasemi-core.h | 5 ++++
> drivers/i2c/busses/i2c-pasemi-platform.c | 6 +++++
> 3 files changed, 36 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-pasemi-core.c b/drivers/i2c/busses/i2c-pasemi-core.c
> index 9028ffb58cc0..4855144b370e 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
>
> @@ -66,6 +67,7 @@ static void pasemi_reset(struct pasemi_smbus *smbus)
> val |= CTL_EN;
>
> reg_write(smbus, REG_CTL, val);
> + reinit_completion(&smbus->irq_completion);
> }
>
> static void pasemi_smb_clear(struct pasemi_smbus *smbus)
> @@ -81,11 +83,18 @@ static int pasemi_smb_waitready(struct pasemi_smbus *smbus)
> int timeout = 10;
> unsigned int status;
>
> - status = reg_read(smbus, REG_SMSTA);
> -
> - while (!(status & SMSTA_XEN) && timeout--) {
> - msleep(1);
> + if (smbus->use_irq) {
> + reinit_completion(&smbus->irq_completion);
> + reg_write(smbus, REG_IMASK, SMSTA_XEN | SMSTA_MTN);
> + wait_for_completion_timeout(&smbus->irq_completion, msecs_to_jiffies(10));
> + reg_write(smbus, REG_IMASK, 0);
> status = reg_read(smbus, REG_SMSTA);
> + } else {
> + status = reg_read(smbus, REG_SMSTA);
> + while (!(status & SMSTA_XEN) && timeout--) {
> + msleep(1);
> + status = reg_read(smbus, REG_SMSTA);
> + }
> }
>
> /* Got NACK? */
> @@ -344,10 +353,14 @@ int pasemi_i2c_common_probe(struct pasemi_smbus *smbus)
>
> /* set up the sysfs linkage to our parent device */
> smbus->adapter.dev.parent = smbus->dev;
> + smbus->use_irq = 0;
> + init_completion(&smbus->irq_completion);
>
> 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 +369,11 @@ 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 = dev_id;
> +
> + complete(&smbus->irq_completion);
I only realized just now that you also want to disable the interrupt right here by writing to IMASK. This is a level sensitive interrupt at AIC level so the moment this handler returns it will fire again until you reach the write above after the completion wait a bit later.
> + return IRQ_HANDLED;
> +}
> diff --git a/drivers/i2c/busses/i2c-pasemi-core.h b/drivers/i2c/busses/i2c-pasemi-core.h
> index 4655124a37f3..88821f4e8a9f 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;
> };
>
> 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..e35945a91dbe 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 +83,11 @@ static int pasemi_platform_i2c_probe(struct platform_device *pdev)
> if (error)
> goto out_clk_disable;
>
> + irq_num = platform_get_irq(pdev, 0);
> + error = devm_request_irq(smbus->dev, 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
>
Sven
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