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Date: Fri, 28 Jan 2022 17:49:13 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Jan Dąbroś <jsd@...ihalf.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-i2c <linux-i2c@...r.kernel.org>,
Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
Mika Westerberg <mika.westerberg@...ux.intel.com>,
Hans de Goede <hdegoede@...hat.com>,
Wolfram Sang <wsa@...nel.org>,
Raul E Rangel <rrangel@...omium.org>,
Marcin Wojtas <mw@...ihalf.com>,
Grzegorz Jaszczyk <jaz@...ihalf.com>, upstream@...ihalf.com,
Tom Lendacky <thomas.lendacky@....com>,
"Deucher, Alexander" <alexander.deucher@....com>,
"Easow, Nimesh" <Nimesh.Easow@....com>,
"Limonciello, Mario" <mario.limonciello@....com>,
kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2 2/2] i2c: designware: Add AMD PSP I2C bus support
On Fri, Jan 28, 2022 at 03:59:40PM +0100, Jan Dąbroś wrote:
> Hi,
>
> Adding proper Andy's email address (and removing wrong one) in the
> whole patchset. Sorry for noise!
Thanks!
> pt., 28 sty 2022 o 15:48 Jan Dabros <jsd@...ihalf.com> napisał(a):
> >
> > Implement an I2C controller sharing mechanism between the host (kernel)
> > and PSP co-processor on some platforms equipped with AMD Cezanne SoC.
> >
> > On these platforms we need to implement "software" i2c arbitration.
> > Default arbitration owner is PSP and kernel asks for acquire as well
> > as inform about release of the i2c bus via mailbox mechanism.
> >
> > +---------+
> > <- ACQUIRE | |
> > +---------| CPU |\
> > | | | \ +----------+ SDA
> > | +---------+ \ | |-------
> > MAILBOX +--> | I2C-DW | SCL
> > | +---------+ | |-------
> > | | | +----------+
> > +---------| PSP |
> > <- ACK | |
> > +---------+
> >
> > +---------+
> > <- RELEASE | |
> > +---------| CPU |
> > | | | +----------+ SDA
> > | +---------+ | |-------
> > MAILBOX +--> | I2C-DW | SCL
> > | +---------+ / | |-------
> > | | | / +----------+
> > +---------| PSP |/
> > <- ACK | |
> > +---------+
> >
> > The solution is similar to i2c-designware-baytrail.c implementation, where
> > we are using a generic i2c-designware-* driver with a small "wrapper".
> >
> > In contrary to baytrail semaphore implementation, beside internal
> > acquire_lock() and release_lock() methods we are also applying quirks to
> > lock_bus() and unlock_bus() global adapter methods. With this in place
> > all i2c clients drivers may lock i2c bus for a desired number of i2c
> > transactions (e.g. write-wait-read) without being aware of that such bus
> > is shared with another entity.
> >
> > Modify i2c_dw_probe_lock_support() to select correct semaphore
> > implementation at runtime, since now we have more than one available.
> >
> > Configure new matching ACPI ID "AMDI0019" and register
> > ARBITRATION_SEMAPHORE flag in order to distinguish setup with PSP
> > arbitration.
> >
> > Add myself as a reviewer for I2C DesignWare in order to help with reviewing
> > and testing possible changes touching new i2c-designware-amdpsp.c module.
> >
> > Signed-off-by: Jan Dabros <jsd@...ihalf.com>
> > Reported-by: kernel test robot <lkp@...el.com>
> > Reported-by: kernel test robot <lkp@...el.com>
New feature can't be reported.
If you want to give a credit to CI, do it in changelog.
...
> > + depends on X86_64
Not sure if it's better than using non-atomic IO helpers.
At least you can't run 32-bit kernels on that platforms
in order to get this functionality working. Doest it mean
those platforms do not have 32-bit compatibility mode
anymore?
...
> > +#include <linux/io-64-nonatomic-lo-hi.h>
Ah, this is not needed if you keep code running exclusively on 64-bit
platforms.
...
> > +struct psp_mbox {
> > + u32 cmd_fields;
> > + phys_addr_t i2c_req_addr;
But phys_addr_t is platform-dependent type. Perhaps you meant to use u64 here
always?
> > +} __packed;
...
> > + struct psp_mbox __iomem *mbox = (struct psp_mbox __iomem *)mbox_iomem;
For void * pointers the cast is implied, i.o.w. it's not needed here.
...
> > +static int psp_send_check_i2c_req(struct psp_i2c_req *req)
> > +{
> > + if (psp_send_cmd(req))
> > + return -EIO;
Why is error code shadowed?
> > + return check_i2c_req_sts(req);
> > +}
...
> > +cleanup:
> > + mutex_unlock(&psp_i2c_access_mutex);
> > + return 0;
Not sure I understand why we ignore all above errors here.
...
> > + if (!dev || !dev->dev)
> > + return -ENODEV;
At which circumstances may we get
dev != NULL
dev->dev == NULL
?
...
> > if (!dev || !dev->dev)
> > - return 0;
> > + return -ENODEV;
I see the same here, perhaps Hans knows the answer :-)
...
> > +static int i2c_dw_probe_lock_support(struct dw_i2c_dev *dev)
> > +{
> > + const struct i2c_dw_semaphore_callbacks *ptr;
> > + int i = 0;
> > + int ret;
> > +
> > + ptr = i2c_dw_semaphore_cb_table;
> > +
> > + dev->semaphore_idx = -1;
> > +
> > + while (ptr->probe) {
> > + ret = ptr->probe(dev);
> > + if (ret) {
> > + /*
> > + * If there is no semaphore device attached to this
> > + * controller, we shouldn't abort general i2c_controller
> > + * probe.
> > + */
> > + if (ret == -ENODEV) {
> > + i++;
> > + ptr++;
> > + continue;
> > + } else {
Redundant 'else', but see below.
> > + return ret;
> > + }
May it be
if (ret != -ENODEV)
return ret;
i++;
ptr++;
continue;
?
> > + }
> > +
> > + dev->semaphore_idx = i;
> > + break;
> > + }
> > +
> > + return 0;
> > +}
--
With Best Regards,
Andy Shevchenko
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