Messages in this thread | | | Date | Thu, 28 Jul 2022 14:19:24 +0530 | Subject | Re: [PATCH 8/8] drm/tidss: Enable Dual and Duplicate Modes for OLDI | From | Aradhya Bhatia <> |
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Hi Tomi,
On 28-Jul-22 12:16, Tomi Valkeinen wrote: > On 27/07/2022 16:22, Tomi Valkeinen wrote: >> Hi, >> >> On 19/07/2022 11:08, Aradhya Bhatia wrote: >>> The AM625 DSS peripheral supports 2 OLDI TXes which can work to enable 2 >>> duplicated displays of smaller resolutions or enable a single Dual-Link >>> display with a higher resolution (1920x1200). >>> >>> Configure the necessary register to enable the different modes. >>> >>> Signed-off-by: Aradhya Bhatia <a-bhatia1@ti.com> >>> --- >>> drivers/gpu/drm/tidss/tidss_dispc.c | 44 +++++++++++++++++++++++++++-- >>> 1 file changed, 41 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c >>> b/drivers/gpu/drm/tidss/tidss_dispc.c >>> index 0b9689453ee8..28cb61259471 100644 >>> --- a/drivers/gpu/drm/tidss/tidss_dispc.c >>> +++ b/drivers/gpu/drm/tidss/tidss_dispc.c >>> @@ -1021,8 +1021,8 @@ static void dispc_enable_oldi(struct >>> dispc_device *dispc, u32 hw_videoport, >>> int count = 0; >>> /* >>> - * For the moment DUALMODESYNC, MASTERSLAVE, MODE, and SRC >>> - * bits of DISPC_VP_DSS_OLDI_CFG are set statically to 0. >>> + * For the moment MASTERSLAVE, and SRC bits of >>> DISPC_VP_DSS_OLDI_CFG are >>> + * set statically to 0. >>> */ >>> if (fmt->data_width == 24) >>> @@ -1039,7 +1039,45 @@ static void dispc_enable_oldi(struct >>> dispc_device *dispc, u32 hw_videoport, >>> oldi_cfg |= BIT(0); /* ENABLE */ >>> - dispc_vp_write(dispc, hw_videoport, DISPC_VP_DSS_OLDI_CFG, >>> oldi_cfg); >>> + /* >>> + * As per all the current implementations of DSS, the OLDI TXes >>> are present only on >>> + * hw_videoport = 0 (OLDI TX 0). However, the config register >>> for 2nd OLDI TX (OLDI TX 1) >>> + * is present in the address space of hw_videoport = 1. Hence, >>> using "hw_videoport + 1" to >>> + * configure OLDI TX 1. >>> + */ >>> + >>> + switch (dispc->oldi_mode) { >>> + case OLDI_MODE_OFF: >>> + oldi_cfg &= ~BIT(0); /* DISABLE */ >>> + dispc_vp_write(dispc, hw_videoport, DISPC_VP_DSS_OLDI_CFG, >>> oldi_cfg); >>> + dispc_vp_write(dispc, hw_videoport + 1, >>> DISPC_VP_DSS_OLDI_CFG, oldi_cfg); >>> + break; >>> + >>> + case OLDI_SINGLE_LINK_SINGLE_MODE_0: >>> + dispc_vp_write(dispc, hw_videoport, DISPC_VP_DSS_OLDI_CFG, >>> oldi_cfg); >>> + break; >>> + >>> + case OLDI_SINGLE_LINK_SINGLE_MODE_1: >>> + dispc_vp_write(dispc, hw_videoport + 1, >>> DISPC_VP_DSS_OLDI_CFG, oldi_cfg); >>> + break; >>> + >>> + case OLDI_SINGLE_LINK_DUPLICATE_MODE: >>> + oldi_cfg |= BIT(5); /* DUPLICATE MODE */ >>> + dispc_vp_write(dispc, hw_videoport, DISPC_VP_DSS_OLDI_CFG, >>> oldi_cfg); >>> + dispc_vp_write(dispc, hw_videoport + 1, >>> DISPC_VP_DSS_OLDI_CFG, oldi_cfg); >>> + break; >>> + >>> + case OLDI_DUAL_LINK: >>> + oldi_cfg |= BIT(11); /* DUALMODESYNC */ >>> + dispc_vp_write(dispc, hw_videoport, DISPC_VP_DSS_OLDI_CFG, >>> oldi_cfg); >>> + dispc_vp_write(dispc, hw_videoport + 1, >>> DISPC_VP_DSS_OLDI_CFG, oldi_cfg); >>> + break; >>> + >>> + default: >>> + dev_warn(dispc->dev, "%s: Incorrect oldi mode. Returning.\n", >>> + __func__); >>> + return; >>> + } >>> while (!(oldi_reset_bit & dispc_read(dispc, DSS_SYSSTATUS)) && >>> count < 10000) >> >> This feels a bit hacky: >> >> - The function is dispc_enable_oldi, but the above code also disables >> oldi. We have code in dispc_vp_unprepare() which disables OLDI at the >> moment. >> >> - The function takes hw_videoport as a parameter, and is designed to >> work on that videoport. The above operates on two videoports. Isn't >> the function also called for hw_videoport +1, which would result in >> reg writes to hw_videoport + 2? >> >> - No matching code in dispc_vp_unprepare >> >> Obviously the duplicate mode (I presume that's "cloning") and the dual >> link complicate things here, and I have to say I haven't worked with >> such setups. But I think somehow this should be restructured so that >> common configuration (common to the OLDIs) is done somewhere else. >> >> I would guess that there are other drivers that support cloning and >> dual mode. Did you have a look how they handle things? > > Oh, I see now... There's just one dss video port for OLDI, the same as > in am65x, but that single video port is now connected to two OLDI TXes. > And thus this function will only be called for the single video port. > > But... The registers for the second OLDI are part of the second video > port (DPI) register block?
Yes! The config register for the second OLDI TX has been (incorrectly) added in the register space for the DPI video port. 'dispc_vp_prepare' is the only function calling 'dispc_enable_oldi', and 'dispc_enable_oldi' would not be called for hw_videoports = 1 (DPI) because of the conditional check.
Hence, to activate both the OLDI-TXes connected to the OLDI video port, I had to use the (hw_videoport + 1) way.
However, I will remove the disable part from the 'dispc_enable_oldi' and I will implement the disabling properly under 'dispc_vp_unprepare', in the next version.
Regards Aradhya
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