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SubjectRe: [PATCH] i2c: piix4: Disable completely the IMC during SMBUS_BLOCK_DATA
On Thu, Sep 21, 2017 at 09:37:43AM +0200, Ricardo Ribalda Delgado wrote:
> SMBUS_BLOCK_DATA transactions might fail due to a race condition with
> the IMC, even when the IMC semaphore is used.
>
> This bug has been reported and confirmed by AMD, who suggested as a
> solution an IMC firmware upgrade (obtained via BIOS update) and
> disabling the IMC during SMBUS_BLOCK_DATA transactions.
>
> Even without the IMC upgrade, the smbus is much more stable with this
> patch.
>
> Tested on a Bettong-alike board.
>
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>

I would very much like a review from Jean for this.

> ---
> drivers/i2c/busses/i2c-piix4.c | 89 ++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 82 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
> index 0ecdb47a23ab..3b8a5eaad956 100644
> --- a/drivers/i2c/busses/i2c-piix4.c
> +++ b/drivers/i2c/busses/i2c-piix4.c
> @@ -85,6 +85,8 @@
> /* SB800 constants */
> #define SB800_PIIX4_SMB_IDX 0xcd6
>
> +#define IMC_SMB_IDX 0x3e
> +
> /*
> * SB800 port is selected by bits 2:1 of the smb_en register (0x2c)
> * or the smb_sel register (0x2e), depending on bit 0 of register 0x2f.
> @@ -160,6 +162,8 @@ struct i2c_piix4_adapdata {
> /* SB800 */
> bool sb800_main;
> u8 port; /* Port number, shifted */
> +
> + bool notify_imc;
> };
>
> static int piix4_setup(struct pci_dev *PIIX4_dev,
> @@ -572,6 +576,50 @@ static s32 piix4_access(struct i2c_adapter * adap, u16 addr,
> return 0;
> }
>
> +static uint8_t piix4_imc_read(uint8_t idx)
> +{
> + outb_p(idx, IMC_SMB_IDX);
> + return inb_p(IMC_SMB_IDX + 1);
> +}
> +
> +static void piix4_imc_write(uint8_t idx, uint8_t value)
> +{
> + outb_p(idx, IMC_SMB_IDX);
> + outb_p(value, IMC_SMB_IDX + 1);
> +}
> +
> +int piix4_imc_sleep(void)
> +{
> + int timeout = MAX_TIMEOUT;
> +
> + piix4_imc_write(0x82, 0x00);
> + piix4_imc_write(0x83, 0xB4);
> + piix4_imc_write(0x80, 0x96);
> +
> + while (timeout--) {
> + if (piix4_imc_read(0x82) == 0xfa)
> + return 0;
> + usleep_range(1000, 2000);
> + }
> +
> + return -ETIMEDOUT;
> +}
> +
> +void piix4_imc_wakeup(void)
> +{
> + int timeout = MAX_TIMEOUT;
> +
> + piix4_imc_write(0x82, 0x00);
> + piix4_imc_write(0x83, 0xB5);
> + piix4_imc_write(0x80, 0x96);
> +
> + while (timeout--) {
> + if (piix4_imc_read(0x82) == 0xfa)
> + break;
> + usleep_range(1000, 2000);
> + }
> +}
> +
> /*
> * Handles access to multiple SMBus ports on the SB800.
> * The port is selected by bits 2:1 of the smb_en register (0x2c).
> @@ -586,7 +634,7 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
> {
> struct i2c_piix4_adapdata *adapdata = i2c_get_adapdata(adap);
> unsigned short piix4_smba = adapdata->smba;
> - int retries = MAX_TIMEOUT;
> + int retries = adapdata->notify_imc ? MAX_TIMEOUT * 2 : MAX_TIMEOUT;
> int smbslvcnt;
> u8 smba_en_lo;
> u8 port;
> @@ -612,6 +660,15 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
> return -EBUSY;
> }
>
> + /* Block data transfers require disabling the imc */
> + if ((size == I2C_SMBUS_BLOCK_DATA) && adapdata->notify_imc)
> + /* If IMC communication fails do not retry*/
> + if (piix4_imc_sleep()) {
> + dev_warn(&adap->dev,
> + "Failed to communicate with the IMC, enable it and/or upgrade your BIOS.\n");
> + adapdata->notify_imc = false;
> + }
> +
> outb_p(piix4_port_sel_sb800, SB800_PIIX4_SMB_IDX);
> smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
>
> @@ -628,6 +685,9 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
> /* Release the semaphore */
> outb_p(smbslvcnt | 0x20, SMBSLVCNT);
>
> + if ((size == I2C_SMBUS_BLOCK_DATA) && adapdata->notify_imc)
> + piix4_imc_wakeup();
> +
> mutex_unlock(&piix4_mutex_sb800);
>
> return retval;
> @@ -679,7 +739,7 @@ static struct i2c_adapter *piix4_main_adapters[PIIX4_MAX_ADAPTERS];
> static struct i2c_adapter *piix4_aux_adapter;
>
> static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
> - bool sb800_main, u8 port,
> + bool sb800_main, u8 port, bool notify_imc,
> const char *name, struct i2c_adapter **padap)
> {
> struct i2c_adapter *adap;
> @@ -707,6 +767,7 @@ static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
> adapdata->smba = smba;
> adapdata->sb800_main = sb800_main;
> adapdata->port = port << 1;
> + adapdata->notify_imc = notify_imc;
>
> /* set up the sysfs linkage to our parent device */
> adap->dev.parent = &dev->dev;
> @@ -728,14 +789,15 @@ static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
> return 0;
> }
>
> -static int piix4_add_adapters_sb800(struct pci_dev *dev, unsigned short smba)
> +static int piix4_add_adapters_sb800(struct pci_dev *dev, unsigned short smba,
> + bool notify_imc)
> {
> struct i2c_piix4_adapdata *adapdata;
> int port;
> int retval;
>
> for (port = 0; port < PIIX4_MAX_ADAPTERS; port++) {
> - retval = piix4_add_adapter(dev, smba, true, port,
> + retval = piix4_add_adapter(dev, smba, true, port, notify_imc,
> piix4_main_port_names_sb800[port],
> &piix4_main_adapters[port]);
> if (retval < 0)
> @@ -769,6 +831,7 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
> dev->device == PCI_DEVICE_ID_ATI_SBX00_SMBUS &&
> dev->revision >= 0x40) ||
> dev->vendor == PCI_VENDOR_ID_AMD) {
> + bool notify_imc = false;
> is_sb800 = true;
>
> if (!request_region(SB800_PIIX4_SMB_IDX, 2, "smba_idx")) {
> @@ -778,6 +841,18 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
> return -EBUSY;
> }
>
> + if (dev->vendor == PCI_VENDOR_ID_AMD &&
> + dev->device == PCI_DEVICE_ID_AMD_KERNCZ_SMBUS) {
> + if (!devm_request_region(&dev->dev, IMC_SMB_IDX, 2,
> + "kerncz_imc_idx")) {
> + dev_warn(&dev->dev,
> + "IMC base address index region 0x%x already in use!\n",
> + SB800_PIIX4_SMB_IDX);
> + } else {
> + notify_imc = true;
> + }
> + }
> +
> /* base address location etc changed in SB800 */
> retval = piix4_setup_sb800(dev, id, 0);
> if (retval < 0) {
> @@ -789,7 +864,7 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
> * Try to register multiplexed main SMBus adapter,
> * give up if we can't
> */
> - retval = piix4_add_adapters_sb800(dev, retval);
> + retval = piix4_add_adapters_sb800(dev, retval, notify_imc);
> if (retval < 0) {
> release_region(SB800_PIIX4_SMB_IDX, 2);
> return retval;
> @@ -800,7 +875,7 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
> return retval;
>
> /* Try to register main SMBus adapter, give up if we can't */
> - retval = piix4_add_adapter(dev, retval, false, 0, "",
> + retval = piix4_add_adapter(dev, retval, false, 0, false, "",
> &piix4_main_adapters[0]);
> if (retval < 0)
> return retval;
> @@ -827,7 +902,7 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
> if (retval > 0) {
> /* Try to add the aux adapter if it exists,
> * piix4_add_adapter will clean up if this fails */
> - piix4_add_adapter(dev, retval, false, 0,
> + piix4_add_adapter(dev, retval, false, 0, false,
> is_sb800 ? piix4_aux_port_name_sb800 : "",
> &piix4_aux_adapter);
> }
> --
> 2.14.1
>
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