[Skiboot] [PATCH] capi: Add a comment for the Transport Control Register

[Frederic Barrat]

Le 17/05/2018 à 15:16, Christophe Lombard a écrit :
> The transport control register needs to be loaded in two steps: Once
> the register values have been set, we have to write bit 63 to a '1',
> which loads the register values into the ci store buffer logic.
> Bit 63 always reads back as a zero but to load the ci store buffer
> values in capp the transition of 0 to 1 of bit 63 must be seen.
> 
> A new comment is added in the code to avoid confusion and to precise
> the feature of this register.
> 
> Signed-off-by: Christophe Lombard <clombard at linux.vnet.ibm.com>
> ---

Reviewed-by: Frederic Barrat <fbarrat at linux.vnet.ibm.com>


>   hw/phb4.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/phb4.c b/hw/phb4.c
> index 18e1e0f..ae584d6 100644
> --- a/hw/phb4.c
> +++ b/hw/phb4.c
> @@ -3764,7 +3764,11 @@ static void phb4_init_capp_regs(struct phb4 *p, uint32_t capp_eng)
>   	}
>   	xscom_write(p->chip_id, TRANSPORT_CONTROL + offset, reg);
> 
> -	/* Initialize CI Store Buffers */
> +	/* The transport control register needs to be loaded in two
> +	 * steps. Once the register values have been set, we have to
> +	 * write bit 63 to a '1', which loads the register values into
> +	 * the ci store buffer logic.
> +	 */
>   	xscom_read(p->chip_id, TRANSPORT_CONTROL + offset, &reg);
>   	reg |= PPC_BIT(63);
>   	xscom_write(p->chip_id, TRANSPORT_CONTROL + offset, reg);
>