linux-kernel - Re: [PATCH 04/16] remoteproc/pru: Add PRU remoteproc driver

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Date:   Fri, 14 Dec 2018 11:53:56 +0200
From:   Roger Quadros <rogerq@...com>
To:     Dimitar Dimitrov <dinuxbg@...il.com>
CC:     <ohad@...ery.com>, <bjorn.andersson@...aro.org>,
        <tony@...mide.com>, <robh+dt@...nel.org>, <bcousson@...libre.com>,
        <ssantosh@...nel.org>, <s-anna@...com>, <nsekhar@...com>,
        <t-kristo@...com>, <nsaulnier@...com>, <jreeder@...com>,
        <m-karicheri2@...com>, <woods.technical@...il.com>,
        <linux-omap@...r.kernel.org>, <linux-remoteproc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        David Lechner <david@...hnology.com>
Subject: Re: [PATCH 04/16] remoteproc/pru: Add PRU remoteproc driver

Hi Dimitar,

On 30/11/18 23:39, Dimitar Dimitrov wrote:
> On Monday, 12/26/2018, 9:52:37 EET Roger Quadros wrote:
>> +/*
>> + * Convert PRU device address (instruction space) to kernel virtual address
>> + *
>> + * A PRU does not have an unified address space. Each PRU has its very own
>> + * private Instruction RAM, and its device address is identical to that of
>> + * its primary Data RAM device address.
>> + */
>> +static void *pru_i_da_to_va(struct pru_rproc *pru, u32 da, int len)
>> +{
>> +       u32 offset;
>> +       void *va = NULL;
>> +
>> +       if (len <= 0)
>> +               return NULL;
> 
> Could you please clear the upper 4 bits the of IRAM device address, in order 
> to support binutils ELF images? Here is an example line to add here:
> 
> +       /* GNU binutils do not support multiple address spaces. The 
> +        * default linker script from the official GNU pru-ld places 
> +        * IRAM at an arbitrary high offset, in order to differentiate it 
> +        * from DRAM. Hence we need to strip the artificial offset 
> +        * from the IRAM address. 
> +        */ 
> +       da &= ~0xf0000000u; 
> +
> 

After some more thought I'm not very sure how to proceed.

I'll be using the below 2 patches in the next patch spin in place of
patch 1 in the current series.
https://lore.kernel.org/lkml/20180623210810.21232-2-david@lechnology.com/
https://lore.kernel.org/lkml/20180623210810.21232-3-david@lechnology.com/

They figure out the PAGE (IRAM vs DRAM) by looking at TI specific section
attributes.

e.g.
[18] .TI.phattrs LOPROC+f000004 00000000 000e08 000010 00 0 0 4
[19] .TI.section.flags LOPROC+f000005 00000000 000e68 00002a 00 0 0 0
[20] .TI.section.page LOPROC+f000007 00000000 000e92 00002a 00 0 0 0

AFAIK the ELF by GNU pru-ld won't contain these sections.

We need to support ELF generated by both tools (TI clpru and GNU pru-ld).
Is it safe to assume that if the ELF doesn't have the TI specific sections
then it was generated by gnupru?

Is there a more straight forward way of differentiating the two. e.g. by looking
at something in the ELF header?

> 
>> +
>> +       if (da >= pru->iram_da &&
>> +           da + len <= pru->iram_da + pru->mem_regions[PRU_MEM_IRAM].size { 
>> +               offset = da - pru->iram_da;
>> +               va = (__force void *)(pru->mem_regions[PRU_MEM_IRAM].va +
>> +                                     offset);
>> +       }
>> +
>> +       return va;
>> +}
> 
> 

cheers,
-roger
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