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    SubjectRe: [PATCH v2 2/2] i2c: piix4: Use request_muxed_region
    On Mon, 26 Feb 2018 12:46:53 -0800, Guenter Roeck wrote:
    > Accesses to SB800_PIIX4_SMB_IDX can occur from multiple drivers.
    > One example for another driver is the sp5100_tco driver.
    >
    > Use request_muxed_region() to ensure synchronization.
    >
    > Signed-off-by: Guenter Roeck <linux@roeck-us.net>
    > ---
    > v2: Dropped now unnecessary include of linux/mutex.h
    > Added error message if request_muxed_region() fails
    > Spell out affected driver in commit message
    >
    > Note that I did not try to do a performance analysis.
    > Doing so seemed excessive, even more so in the context of
    > piix4_imc_sleep() already using request_muxed_region().
    >
    > drivers/i2c/busses/i2c-piix4.c | 55 +++++++++++++++++++-----------------------
    > 1 file changed, 25 insertions(+), 30 deletions(-)
    >
    > diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
    > index 4c1f6aaec0fc..90946a8b9a75 100644
    > --- a/drivers/i2c/busses/i2c-piix4.c
    > +++ b/drivers/i2c/busses/i2c-piix4.c
    > @@ -40,7 +40,6 @@
    > #include <linux/dmi.h>
    > #include <linux/acpi.h>
    > #include <linux/io.h>
    > -#include <linux/mutex.h>
    >
    >
    > /* PIIX4 SMBus address offsets */
    > @@ -153,10 +152,7 @@ static const struct dmi_system_id piix4_dmi_ibm[] = {
    >
    > /*
    > * SB800 globals
    > - * piix4_mutex_sb800 protects piix4_port_sel_sb800 and the pair
    > - * of I/O ports at SB800_PIIX4_SMB_IDX.
    > */
    > -static DEFINE_MUTEX(piix4_mutex_sb800);
    > static u8 piix4_port_sel_sb800;
    > static u8 piix4_port_mask_sb800;
    > static u8 piix4_port_shift_sb800;
    > @@ -298,12 +294,19 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
    > else
    > smb_en = (aux) ? 0x28 : 0x2c;
    >
    > - mutex_lock(&piix4_mutex_sb800);
    > + if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2, "sb800_piix4_smb")) {
    > + dev_err(&PIIX4_dev->dev,
    > + "SMB base address index region 0x%x already in use.\n",
    > + SB800_PIIX4_SMB_IDX);
    > + return -EBUSY;
    > + }
    > +
    > outb_p(smb_en, SB800_PIIX4_SMB_IDX);
    > smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
    > outb_p(smb_en + 1, SB800_PIIX4_SMB_IDX);
    > smba_en_hi = inb_p(SB800_PIIX4_SMB_IDX + 1);
    > - mutex_unlock(&piix4_mutex_sb800);
    > +
    > + release_region(SB800_PIIX4_SMB_IDX, 2);
    >
    > if (!smb_en) {
    > smb_en_status = smba_en_lo & 0x10;
    > @@ -373,7 +376,12 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
    > break;
    > }
    > } else {
    > - mutex_lock(&piix4_mutex_sb800);
    > + if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2,
    > + "sb800_piix4_smb")) {
    > + release_region(piix4_smba, SMBIOSIZE);
    > + return -EBUSY;
    > + }
    > +
    > outb_p(SB800_PIIX4_PORT_IDX_SEL, SB800_PIIX4_SMB_IDX);
    > port_sel = inb_p(SB800_PIIX4_SMB_IDX + 1);
    > piix4_port_sel_sb800 = (port_sel & 0x01) ?
    > @@ -381,7 +389,7 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
    > SB800_PIIX4_PORT_IDX;
    > piix4_port_mask_sb800 = SB800_PIIX4_PORT_IDX_MASK;
    > piix4_port_shift_sb800 = SB800_PIIX4_PORT_IDX_SHIFT;
    > - mutex_unlock(&piix4_mutex_sb800);
    > + release_region(SB800_PIIX4_SMB_IDX, 2);
    > }
    >
    > dev_info(&PIIX4_dev->dev,
    > @@ -679,7 +687,8 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
    > u8 port;
    > int retval;
    >
    > - mutex_lock(&piix4_mutex_sb800);
    > + if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2, "sb800_piix4_smb"))
    > + return -EBUSY;
    >
    > /* Request the SMBUS semaphore, avoid conflicts with the IMC */
    > smbslvcnt = inb_p(SMBSLVCNT);
    > @@ -695,8 +704,8 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
    > } while (--retries);
    > /* SMBus is still owned by the IMC, we give up */
    > if (!retries) {
    > - mutex_unlock(&piix4_mutex_sb800);
    > - return -EBUSY;
    > + retval = -EBUSY;
    > + goto release;
    > }
    >
    > /*
    > @@ -753,8 +762,8 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
    > if ((size == I2C_SMBUS_BLOCK_DATA) && adapdata->notify_imc)
    > piix4_imc_wakeup();
    >
    > - mutex_unlock(&piix4_mutex_sb800);
    > -
    > +release:
    > + release_region(SB800_PIIX4_SMB_IDX, 2);
    > return retval;
    > }
    >
    > @@ -899,13 +908,6 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
    > bool notify_imc = false;
    > is_sb800 = true;
    >
    > - if (!request_region(SB800_PIIX4_SMB_IDX, 2, "smba_idx")) {
    > - dev_err(&dev->dev,
    > - "SMBus base address index region 0x%x already in use!\n",
    > - SB800_PIIX4_SMB_IDX);
    > - return -EBUSY;
    > - }
    > -
    > if (dev->vendor == PCI_VENDOR_ID_AMD &&
    > dev->device == PCI_DEVICE_ID_AMD_KERNCZ_SMBUS) {
    > u8 imc;
    > @@ -922,20 +924,16 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
    >
    > /* base address location etc changed in SB800 */
    > retval = piix4_setup_sb800(dev, id, 0);
    > - if (retval < 0) {
    > - release_region(SB800_PIIX4_SMB_IDX, 2);
    > + if (retval < 0)
    > return retval;
    > - }
    >
    > /*
    > * Try to register multiplexed main SMBus adapter,
    > * give up if we can't
    > */
    > retval = piix4_add_adapters_sb800(dev, retval, notify_imc);
    > - if (retval < 0) {
    > - release_region(SB800_PIIX4_SMB_IDX, 2);
    > + if (retval < 0)
    > return retval;
    > - }
    > } else {
    > retval = piix4_setup(dev, id);
    > if (retval < 0)
    > @@ -983,11 +981,8 @@ static void piix4_adap_remove(struct i2c_adapter *adap)
    >
    > if (adapdata->smba) {
    > i2c_del_adapter(adap);
    > - if (adapdata->port == (0 << piix4_port_shift_sb800)) {
    > + if (adapdata->port == (0 << piix4_port_shift_sb800))
    > release_region(adapdata->smba, SMBIOSIZE);
    > - if (adapdata->sb800_main)
    > - release_region(SB800_PIIX4_SMB_IDX, 2);
    > - }
    > kfree(adapdata);
    > kfree(adap);
    > }

    Reviewed-by: Jean Delvare <jdelvare@suse.de>

    --
    Jean Delvare
    SUSE L3 Support

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