On Mon, Mar 11, 2019 at 09:36:27PM +0530, Jagan Teki wrote: > On Mon, Mar 11, 2019 at 9:08 PM Maxime Ripard <maxime.ripard@xxxxxxxxxxx> wrote: > > > > On Mon, Mar 11, 2019 at 07:06:24PM +0530, Jagan Teki wrote: > > > pll-video => pll-mipi => tcon0 => tcon0-pixel-clock is the typical > > > MIPI clock topology in Allwinner DSI controller. > > > > > > TCON dotclock driver is computing the desired DCLK divider based on > > > panel pixel clock along with input DCLK min, max divider values from > > > tcon driver and that would eventually set the pll-mipi clock rate. > > > > > > The current code allows the TCON clock divider to have a default 4 > > > for min, max ranges that would fail to compute the desired pll-mipi > > > rate while supporting new panels. > > > > > > So, add the computation logic 'format/lanes' to dclk min and max dividers > > > and instead of default 4. This computation logic align with Allwinner A64 > > > BSP, hoping that would work even for A33. > > > > Last time we discussed this, we found out that this wasn't the case, > > even in the BSP. > > This was the case for BSP to compute pll-mipi not for TCON_DSI clock > register, SUN4I_TCON0_DCLK_REG, which marked the divider 4 by default. > > > What compelling evidence have you found that makes you say otherwise? > > divider 4 isn't worked, this I would mentioned before as well. Maybe you mentionned it before, but it's nowhere to be found in your commit log. > Tested this on 4 different panels, and below are the desired divider values > and pll-mipi clock rate with respect to pixel clock frequency. > > - 55MHz pixel clock with 4-lane panel, and the desired DSI clock divider > is 6 with the output parent clock rate of 330MHz. > - 30MHz pixel clock with 4-lane panel, and the desired DSI clock divider > is 6 with parent clock rate of 180MHz. > - 27.5Mhz pixel clock with 2-lane pane, and the desired DSI clock divider > is 12 with the output parent clock rate of 330MHz. > - 147MHz pixel clock with 4-lane panel, and the desired DSI clock divider > is 6 with the output parent clock rate of 882MHz. > > BSP trying to use this format/lane to compute dsi divider that in-turn > using pll-mipi set_rate but TCON0_DCLK_REG keep constant 4. Feel free to reply to http://lists.infradead.org/pipermail/linux-arm-kernel/2019-February/629596.html And correct whatever is said there that isn't what is happening. Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
Attachment:
signature.asc
Description: PGP signature
