On 08/20/2018 05:26 PM, miny...@acm.org wrote:
> From: Corey Minyard <cminy...@mvista.com>
>
> Change 880b1ffe6ec2f0ae "smbus: do not immediately complete commands"
> changed pm_smbus to delay setting the host busy bit until the status
> register was read, to work around a bug in AMIBIOS. Unfortunately,
> when interrupts are enabled, the status register will never get read
> and the processing will never happen.
>
> Modify the code to only delay setting the host busy bit if interrupts
> are not enabled.
>
> Signed-off-by: Corey Minyard <cminy...@mvista.com>
> Cc: Hervé Poussineau <hpous...@reactos.org>
> Cc: Philippe Mathieu-Daudé <f4...@amsat.org>
Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>
> ---
> hw/i2c/pm_smbus.c | 19 +++++++++++++------
> 1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/hw/i2c/pm_smbus.c b/hw/i2c/pm_smbus.c
> index 664a6b1..10ba208 100644
> --- a/hw/i2c/pm_smbus.c
> +++ b/hw/i2c/pm_smbus.c
> @@ -80,9 +80,6 @@ static void smb_transaction(PMSMBus *s)
> I2CBus *bus = s->smbus;
> int ret;
>
> - assert(s->smb_stat & STS_HOST_BUSY);
> - s->smb_stat &= ~STS_HOST_BUSY;
> -
> SMBUS_DPRINTF("SMBus trans addr=0x%02x prot=0x%02x\n", addr, prot);
> /* Transaction isn't exec if STS_DEV_ERR bit set */
> if ((s->smb_stat & STS_DEV_ERR) != 0) {
> @@ -209,9 +206,18 @@ error:
>
> static void smb_transaction_start(PMSMBus *s)
> {
> - /* Do not execute immediately the command ; it will be
> - * executed when guest will read SMB_STAT register */
> - s->smb_stat |= STS_HOST_BUSY;
> + if (s->smb_ctl & CTL_INTREN) {
> + smb_transaction(s);
> + } else {
> + /* Do not execute immediately the command; it will be
> + * executed when guest will read SMB_STAT register. This
> + * is to work around a bug in AMIBIOS (that is working
> + * around another bug in some specific hardware) where
> + * it waits for STS_HOST_BUSY to be set before waiting
> + * checking for status. If STS_HOST_BUSY doesn't get
> + * set, it gets stuck. */
> + s->smb_stat |= STS_HOST_BUSY;
> + }
> }
>
> static bool
> @@ -330,6 +336,7 @@ static uint64_t smb_ioport_readb(void *opaque, hwaddr
> addr, unsigned width)
> val = s->smb_stat;
> if (s->smb_stat & STS_HOST_BUSY) {
> /* execute command now */
> + s->smb_stat &= ~STS_HOST_BUSY;
> smb_transaction(s);
> }
> break;
>
