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During the initialization, the kernel writes to the frame buffer using printk and I can see it on the LCD.
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<div style="LINE-HEIGHT: 15pt">But when I am writing in the busybox (which is user program seen from the kernel) using 'printf', this page error occurs.</div>
<div style="LINE-HEIGHT: 15pt">For both printk and printf cases, the context table base is the same, but one(printk) is in context 0 while the otehr is in context 1.</div>
<div style="LINE-HEIGHT: 15pt">(but all the contexts have the same pgd values in both cases, each with different value for printk and printf because they are different process.</div>
<div style="LINE-HEIGHT: 15pt">and different threads in a process have different context I understand). The frame buffer address appears the same in both printk and printf.</div>
<div style="LINE-HEIGHT: 15pt">I've got the frame buffer address using dma_alloc_writecombine function (I tried with dma_alloc_coherent, but it fails with error in our system).</div>
<div style="LINE-HEIGHT: 15pt">I guess there should be some typical cases when this happens. (I know the page fault routine should assign a virtual address for the page frame containing the frame buffer and connect it to the page table for the context but
it could not handle it. I will delve into it anyway..)</div>
<div style="LINE-HEIGHT: 15pt">Any hint? I hope somebody could shed some light to this problem.</div>
<div style="LINE-HEIGHT: 15pt">Thanks,</div>
<div style="LINE-HEIGHT: 15pt">Chan</div>
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<div style="LINE-HEIGHT: 15pt"><b>From : </b>"Valdis.Kletnieks@vt.edu" <Valdis.Kletnieks@vt.edu><br>
<b>Sent : </b>2014-03-28 01:29:21 ( +09:00 )<br>
<b>To : </b>Chan Kim <ckim@etri.re.kr><br>
<b>Cc : </b>kernelnewbies@kernelnewbies.org <kernelnewbies@kernelnewbies.org><br>
<b>Subject : </b>Re: Unable to handle kernel paging request at virtual address ... while writing to frame buffer..<br>
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On Thu, 27 Mar 2014 08:55:10 -0000, Chan Kim said:<br>
> I have this 'unable to handle kernel paging request at virtual address ...'<br>
> when writing to the frame buffer.<br>
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That almost certainly means you tried to write to something other than<br>
the actual frame buffer.<br>
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