Messages in this thread | | | Date | Fri, 28 Jan 2022 17:49:13 +0200 | From | Andy Shevchenko <> | Subject | Re: [PATCH v2 2/2] i2c: designware: Add AMD PSP I2C bus support |
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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@semihalf.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@semihalf.com>
> > Reported-by: kernel test robot <lkp@intel.com> > > Reported-by: kernel test robot <lkp@intel.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.
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> > +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.
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> > + if (!dev || !dev->dev) > > + return -ENODEV;
At which circumstances may we get dev != NULL dev->dev == NULL ?
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> > if (!dev || !dev->dev) > > - return 0; > > + return -ENODEV;
I see the same here, perhaps Hans knows the answer :-)
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> > +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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