On 1/10/22 7:32 PM, Sakari Ailus wrote: > On Wed, Dec 29, 2021 at 10:00:43AM +0000, Cao, Bingbu wrote: >> Hi Sakari, >> >> Thanks for your review. >> >> ________________________ >> BRs, >> Bingbu Cao >> >>> -----Original Message----- >>> From: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> >>> Sent: Wednesday, December 29, 2021 5:42 PM >>> To: Cao, Bingbu <bingbu.cao@xxxxxxxxx> >>> Cc: linux-media@xxxxxxxxxxxxxxx; Tu, ShawnX <shawnx.tu@xxxxxxxxx>; >>> senozhatsky@xxxxxxxxxxxx; tfiga@xxxxxxxxxxxx; bingbu.cao@xxxxxxxxxxxxxxx; >>> Yeh, Andy <andy.yeh@xxxxxxxxx> >>> Subject: Re: [PATCH] media: ov5675: use group write to update digital >>> gain >>> >>> Hi Bingbu, >>> >>> On Wed, Dec 29, 2021 at 04:57:39PM +0800, Bingbu Cao wrote: >>>> MWB gain register are used to set gain for each mwb channel mannually. >>>> However, it will involve some artifacts at low light environment as >>>> gain cannot be applied to each channel synchronously. Update the >>>> driver to use group write for digital gain to make the sure RGB >>>> digital gain be applied together at frame boundary. >>> >>> How about the analogue gain and exposure time? >>> >>> Shouldn't they be applied similarly as well? Adding two more writes >>> increases the probability of missing a frame there. >> >> We did not meet issue related to analog gain as the it was applied by only >> 1 reg write, it looks like same issue we found on ov8856, changing to set >> digital gain by only 1 global gain write will fix the problem. > > That device is different in its support for global digital gain. This patch > sets the gain for each component separately. > > Adding more writes on a given frame increases the probability of slipping > to the following frame. Doing the exposure and gain updates in the same > group write would alleviate that a little. Sakari, It is feasible to put the exposure and gain update in a same group, however, lunching the group at different time may increase the probability of slipping as well. What do you think? > >> >>> >>> This is of course a trick since the control framework doesn't really >>> support this, but I think this support should be added. >>> >>> -- >>> Regards, >>> >>> Sakari Ailus > -- Best regards, Bingbu Cao
