Hi Koji-san, Kieran(-san),
Thanks for your work.
On 2018-12-10 12:29:01 +0000, Kieran Bingham wrote:
> From: Koji Matsuoka <koji.matsuoka.xm@xxxxxxxxxxx>
>
> The ADV7481 Register Control Manual states that bit 2 in the Video
> Standard Selection register is reserved with the value of 1.
>
> The bit is otherwise undocumented, and currently cleared by the driver
> when setting the video standard selection.
>
> Define the bit as reserved, and ensure that it is always set when
> writing to the SDP_VID_SEL register.
>
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
> Signed-off-by: Koji Matsuoka <koji.matsuoka.xm@xxxxxxxxxxx>
> [Kieran: Updated commit message, utilised BIT macro]
> Signed-off-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
> ---
> drivers/media/i2c/adv748x/adv748x-afe.c | 3 ++-
> drivers/media/i2c/adv748x/adv748x.h | 1 +
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/i2c/adv748x/adv748x-afe.c b/drivers/media/i2c/adv748x/adv748x-afe.c
> index 71714634efb0..c4d9ffc50702 100644
> --- a/drivers/media/i2c/adv748x/adv748x-afe.c
> +++ b/drivers/media/i2c/adv748x/adv748x-afe.c
> @@ -151,7 +151,8 @@ static void adv748x_afe_set_video_standard(struct adv748x_state *state,
> int sdpstd)
> {
> sdp_clrset(state, ADV748X_SDP_VID_SEL, ADV748X_SDP_VID_SEL_MASK,
> - (sdpstd & 0xf) << ADV748X_SDP_VID_SEL_SHIFT);
> + (sdpstd & 0xf) << ADV748X_SDP_VID_SEL_SHIFT |
> + ADV748X_SDP_VID_RESERVED_BIT);
Is this really needed? In practice the adv748x driver never touches the
reserved bit and this special handling *should* not be needed :-)
#define sdp_clrset(s, r, m, v) sdp_write(s, r, (sdp_read(s, r) & ~m) | v)
The full 'user_map_rw_reg_02' register where the upper 4 bits are
vid_sel subregister is read and masked. Then the value is updated with
the new vid_sel value and written back.
However if this is needed or fixes a real bug I'm not against this
change but in such case I feel the mask should be updated to reflect
which bits are touched.
> }
>
> static int adv748x_afe_s_input(struct adv748x_afe *afe, unsigned int input)
> diff --git a/drivers/media/i2c/adv748x/adv748x.h b/drivers/media/i2c/adv748x/adv748x.h
> index b482c7fe6957..778aa55a741a 100644
> --- a/drivers/media/i2c/adv748x/adv748x.h
> +++ b/drivers/media/i2c/adv748x/adv748x.h
> @@ -265,6 +265,7 @@ struct adv748x_state {
> #define ADV748X_SDP_INSEL 0x00 /* user_map_rw_reg_00 */
>
> #define ADV748X_SDP_VID_SEL 0x02 /* user_map_rw_reg_02 */
> +#define ADV748X_SDP_VID_RESERVED_BIT BIT(2) /* undocumented reserved bit */
> #define ADV748X_SDP_VID_SEL_MASK 0xf0
> #define ADV748X_SDP_VID_SEL_SHIFT 4
>
> --
> 2.17.1
>
--
Regards,
Niklas Söderlund
