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Commit 701dc207 authored by Ricardo Ribalda Delgado's avatar Ricardo Ribalda Delgado Committed by Wolfram Sang
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i2c: piix4: Avoid race conditions with IMC 

On AMD's SB800 and upwards, the SMBus is shared with the Integrated
Micro Controller (IMC).

The platform provides a hardware semaphore to avoid race conditions
among them. (Check page 288 of the SB800-Series Southbridges Register
Reference Guide http://support.amd.com/TechDocs/45482.pdf

)

Without this patch, many access to the SMBus end with an invalid
transaction or even with the bus stalled.

Reported-by: default avatarAlexandre Desnoyers <alex@qtec.com>
Signed-off-by: default avatarRicardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com&gt;:>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 2659161d

drivers/i2c/busses/i2c-piix4.c

+22 −0
Original line number Diff line number Diff line
@@ -585,10 +585,29 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr, 
		 u8 command, int size, union i2c_smbus_data *data)

{

	struct i2c_piix4_adapdata *adapdata = i2c_get_adapdata(adap);

	unsigned short piix4_smba = adapdata->smba;

	int retries = MAX_TIMEOUT;

	int smbslvcnt;

	u8 smba_en_lo;

	u8 port;

	int retval;



	/* Request the SMBUS semaphore, avoid conflicts with the IMC */

	smbslvcnt  = inb_p(SMBSLVCNT);

	do {

		outb_p(smbslvcnt | 0x10, SMBSLVCNT);



		/* Check the semaphore status */

		smbslvcnt  = inb_p(SMBSLVCNT);

		if (smbslvcnt & 0x10)

			break;



		usleep_range(1000, 2000);

	} while (--retries);

	/* SMBus is still owned by the IMC, we give up */

	if (!retries)

		return -EBUSY;



	mutex_lock(&piix4_mutex_sb800);



	outb_p(piix4_port_sel_sb800, SB800_PIIX4_SMB_IDX);
@@ -606,6 +625,9 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr, 


	mutex_unlock(&piix4_mutex_sb800);



	/* Release the semaphore */

	outb_p(smbslvcnt | 0x20, SMBSLVCNT);



	return retval;

}