1 // SPDX-License-Identifier: GPL-2.0-only
3  * IOSF-SB MailBox Interface Driver
6  * The IOSF-SB is a fabric bus available on Atom based SOC's that uses a
44 		return -ENODEV;  in iosf_mbi_pci_read_mdr()
64 	dev_err(&mbi_pdev->dev, "PCI config access failed with %d\n", result);  in iosf_mbi_pci_read_mdr()
73 		return -ENODEV;  in iosf_mbi_pci_write_mdr()
93 	dev_err(&mbi_pdev->dev, "PCI config access failed with %d\n", result);  in iosf_mbi_pci_write_mdr()
106 		return -EPERM;  in iosf_mbi_read()
129 		return -EPERM;  in iosf_mbi_write()
153 		return -EPERM;  in iosf_mbi_modify()
184 	/* Mbi isn't hot-pluggable. No remove routine is provided */  in iosf_mbi_available()
190  **************** P-Unit/kernel shared I2C bus arbitration ****************
192  * Some Bay Trail and Cherry Trail devices have the P-Unit and us (the kernel)
193  * share a single I2C bus to the PMIC. Below are helpers to arbitrate the
194  * accesses between the kernel and the P-Unit.
196  * See arch/x86/include/asm/iosf_mbi.h for kernel-doc text for each function.
216 	/* Wait for any I2C PMIC accesses from in kernel drivers to finish. */  in iosf_mbi_punit_acquire()
226 	 * the PMIC, other then block in kernel accesses to the PMIC.  in iosf_mbi_punit_acquire()
238 	iosf_mbi_pmic_punit_access_count--;  in iosf_mbi_punit_release()
254 		dev_err(&mbi_pdev->dev, "Error P-Unit semaphore read failed\n");  in iosf_mbi_get_sem()
266 		dev_err(&mbi_pdev->dev, "Error P-Unit semaphore reset failed\n");  in iosf_mbi_reset_semaphore()
275  * This function blocks P-Unit accesses to the PMIC I2C bus, so that kernel
276  * I2C code, such as e.g. a fuel-gauge driver, can access it safely.
279  * already blocked P-Unit accesses because it wants them blocked over multiple
280  * i2c-transfers, for e.g. read-modify-write of an I2C client register.
282  * To allow safe PMIC i2c bus accesses this function takes the following steps:
284  * 1) Some code sends request to the P-Unit which make it access the PMIC
285  *    I2C bus. Testing has shown that the P-Unit does not check its internal
286  *    PMIC bus semaphore for these requests. Callers of these requests call
287  *    iosf_mbi_punit_acquire()/_release() around their P-Unit accesses, these
295  * 3) Some code makes such P-Unit requests from atomic contexts where it
298  *    needing P-Unit resources from atomic context to acquire them before
299  *    we take control over the PMIC I2C bus.
301  * 4) When CPU cores enter C6 or C7 the P-Unit needs to talk to the PMIC
302  *    if this happens while the kernel itself is accessing the PMIC I2C bus
307  * 5) The P-Unit has a PMIC bus semaphore which we can request to stop
308  *    autonomous P-Unit tasks from accessing the PMIC I2C bus while we hold it.
319 		return -ENXIO;  in iosf_mbi_block_punit_i2c_access()
338 	 * requires the P-Unit to talk to the PMIC and if this happens while  in iosf_mbi_block_punit_i2c_access()
347 		dev_err(&mbi_pdev->dev, "Error P-Unit semaphore request failed\n");  in iosf_mbi_block_punit_i2c_access()
358 			dev_dbg(&mbi_pdev->dev, "P-Unit semaphore acquired after %ums\n",  in iosf_mbi_block_punit_i2c_access()
359 				jiffies_to_msecs(jiffies - start));  in iosf_mbi_block_punit_i2c_access()
366 	ret = -ETIMEDOUT;  in iosf_mbi_block_punit_i2c_access()
367 	dev_err(&mbi_pdev->dev, "Error P-Unit semaphore timed out, resetting\n");  in iosf_mbi_block_punit_i2c_access()
371 		dev_err(&mbi_pdev->dev, "P-Unit semaphore: %d\n", sem);  in iosf_mbi_block_punit_i2c_access()
387 	iosf_mbi_pmic_i2c_access_count--;  in iosf_mbi_unblock_punit_i2c_access()
390 		dev_dbg(&mbi_pdev->dev, "punit semaphore held for %ums\n",  in iosf_mbi_unblock_punit_i2c_access()
391 			jiffies_to_msecs(jiffies - iosf_mbi_sem_acquired));  in iosf_mbi_unblock_punit_i2c_access()
454 		return -EACCES;  in mcr_set()
483 	/* mcr - initiates mailbox transaction */  in iosf_sideband_debug_init()
508 		dev_err(&pdev->dev, "error: could not enable device\n");  in iosf_mbi_probe()
513 	iosf_mbi_sem_address = dev_id->driver_data;  in iosf_mbi_probe()