AM5728: DSS initialization after reset

Michi Yama

Part Number: AM5728
Other Parts Discussed in Thread: SYSCONFIG

Hi,
I have one question regarding AM5728's DSS(Display controller) initialization.

Is this Display subsystem needed some software reset after PORz is de-asserted?

According to i862 "Reset Should Use PORz" of AM5728 silicon Errata, software reset
is not 100% reliable, and SoC may hang during boot after the reset source is de-asserted.

So I think DSS does not need to use software reset after PORz is de-asserted.
But my customer's display driver (this is not Linux based) uses the software reset in its initialization sequence. And customer found this software reset causes abnormal situation(SGX initialization failed). This software reset is executed before SGX initialization sequence. When customer remove the software reset from display driver, the symptom disappeared.

So we would like to confirm whether the DSS needs to issue the software reset in initialization sequence after PORz de-asserted.

Please advise me.

I appreciate your quick reply.

Best regards,

Michi

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

Hi,

PORz is a global reset and propagates through all device subsystems. Everything in the device is reset.

0 Michi Yama over 8 years ago in reply to Biser Gatchev-XID

Guru 10030 points

Dear Biser-san,
Thank you for your quick reply.

I know POR is global reset. What I would like to know is whether Display Subsystem requires software reset while initialization sequence, or not. Or do you know any transaction taht softwre reset is needed in DSS?

Please advise me again.

Best regards,
Michi

0 Biser Gatchev-XID over 8 years ago in reply to Michi Yama

TI__Guru**** 393215 points

I think I explained that the PORz resets ALL device subsystems. Why should you need a software reset afterwards?

0 Michi Yama over 8 years ago in reply to Biser Gatchev-XID

Guru 10030 points

Dear Biser-san,

Thank you for your quick reply again.

I change my question.

As you know, DISPC_SYSCONFIG register has SOFTRESET bit. If this bit is set, DSS module is reset.
But AM5728 has i862 errata. So this reset bit should not be used for reset. And if this bit is used for reset, DSS may hang in some case.
Is my understanding right?

I appreciate your continuous support.

Best regards,
Michi

0 Biser Gatchev-XID over 8 years ago in reply to Michi Yama

TI__Guru**** 393215 points

Errata i862 concerns only global resets, not local subsystem resets. I suggest your customers study the code provided in one of the AM57x SDK's and use it as a reference when writing their own code: www.ti.com/.../PROCESSOR-SDK-AM57X

0 Michi Yama over 8 years ago in reply to Biser Gatchev-XID

Guru 10030 points

Dear Biser-san,

Thank you for your support.

I would like to ask you one more thing.

According to Figure 11-5 Display Subsystem Reset Scheme of AM5728 TRM(spruhz6e), DSS_RST and SR(internal module software reset) are ored. And the DSS_RST is occurred by SYS_PWRON_RST(PORz). The DSS_RST resets entirely Disply subsystem. For this reason, customer does not need to do software reset to DSS after PORz de-assertion.
Is my understanding right?

I appreciate your continuous support.

Best regards,
Michi

0 Biser Gatchev-XID over 8 years ago in reply to Michi Yama

TI__Guru**** 393215 points

Yes, correct.

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AM5728: DSS initialization after reset