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Subject: Re: [Regression 5.6-rc1][Bisected b6231ea2b3c6] Powerpc 8xx doesn't
 boot anymore
From:   Christophe Leroy <christophe.leroy@c-s.fr>
To:     Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Li Yang <leoyang.li@nxp.com>, Qiang Zhao <qiang.zhao@nxp.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Scott Wood <oss@buserror.net>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-arm-kernel@lists.infradead.org
References: <0d45fa64-51ee-0052-cb34-58c770c5b3ce@c-s.fr>
Message-ID: <aee10440-c244-7c93-d3bb-fd29d8a83be4@c-s.fr>
Date:   Wed, 12 Feb 2020 14:50:10 +0000
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On 02/12/2020 02:24 PM, Christophe Leroy wrote:
> Hi Rasmus,
> 
> Kernel 5.6-rc1 silently fails on boot.
> 
> I bisected the problem to commit b6231ea2b3c6 ("soc: fsl: qe: drop 
> broken lazy call of cpm_muram_init()")
> 
> I get a bad_page_fault() for an access at address 8 in 
> cpm_muram_alloc_common(), called from cpm_uart_console_setup() via 
> cpm_uart_allocbuf()
> 
> Reverting the guilty commit on top of 5.6-rc1 is not trivial.
> 
> In your commit text you explain that cpm_muram_init() is called via 
> subsys_initcall. But console init is done before that, so it cannot work.
> 
> Do you have a fix for that ?
> 

The following patch allows powerpc 8xx to boot again. Don't know if 
that's the good place and way to do the fix though.

---
diff --git a/drivers/tty/serial/cpm_uart/cpm_uart_core.c 
b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
index 4cabded8390b..341d682ec6eb 100644
--- a/drivers/tty/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
@@ -1351,6 +1351,7 @@ static int __init cpm_uart_console_setup(struct 
console *co, char *options)
  		clrbits32(&pinfo->sccp->scc_gsmrl, SCC_GSMRL_ENR | SCC_GSMRL_ENT);
  	}

+	cpm_muram_init();
  	ret = cpm_uart_allocbuf(pinfo, 1);

  	if (ret)

---
Christophe