Re: [PATCH 5/6] remoteproc: mtk_apu: Don't try to use the APU local RAM

Mathieu Poirier
2020-07-21T20:43:37Z

On Mon, Jul 13, 2020 at 03:29:26PM +0200, Alexandre Bailon wrote:
> Currently, this local RAM is not accessible from the CPU.
> If the CPU tries to access it, then the CPU will hang.
>
> Remoteproc may try to use it when it load a firmware
> that has some sections in the local RAM.
> This workarounds the issue by skiping this section.
>
> Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
> ---
> drivers/remoteproc/mtk_apu_rproc.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/remoteproc/mtk_apu_rproc.c b/drivers/remoteproc/mtk_apu_rproc.c
> index 565b3adca5de..e16d3258a785 100644
> --- a/drivers/remoteproc/mtk_apu_rproc.c
> +++ b/drivers/remoteproc/mtk_apu_rproc.c
> @@ -57,6 +57,9 @@
> #define CORE_DEFAULT2_SPIDEN BIT(0)
> #define CORE_XTENSA_ALTRESETVEC (0x000001F8)
>
> +#define DRAM0_START (0x7ff00000)
> +#define IRAM0_END (0x7ff80000)
> +
> struct mtk_vpu_rproc {
> struct device *dev;
> struct rproc *rproc;
> @@ -139,6 +142,7 @@ static void mtk_vpu_rproc_kick(struct rproc *rproc, int vqid)
>
> int mtk_vpu_elf_sanity_check(struct rproc *rproc, const struct firmware *fw)
> {
> + struct mtk_vpu_rproc *vpu_rproc = rproc->priv;
> const u8 *elf_data = fw->data;
> struct elf32_hdr *ehdr;
> struct elf32_phdr *phdr;
> @@ -156,6 +160,16 @@ int mtk_vpu_elf_sanity_check(struct rproc *rproc, const struct firmware *fw)
> /* Remove empty PT_LOAD section */
> if (phdr->p_type == PT_LOAD && !phdr->p_paddr)
> phdr->p_type = PT_NULL;
> + /*
> + * Workaround: Currently, the CPU can't access to the APU
> + * local RAM. This removes the local RAM section from the
> + * firmware. Please note that may cause some issues.
> + */
> + if (phdr->p_paddr >= DRAM0_START && phdr->p_paddr < IRAM0_END) {
> + dev_warn_once(vpu_rproc->dev,
> + "Skipping the APU local RAM section\n");
> + phdr->p_type = PT_NULL;

We can't selectively decide to not load sections of a program due to a platform
driver shortcoming. Either a real solution is found or booting the remote
processor is interrupted, with a strong incline toward the former.

I guess you're dealing with tightly coupled memory or on-chip RAM areas -
both are accessed on other platform using ioremap_wc() or devm_ioremap_wc().
You might want to try doing what Suman has done in this patchset [1], with
specific attention to TCMs and SRAM.

Thanks,
Mathieu

[1]. https://patchwork.kernel.org/project/linux-remoteproc/list/?series=310325

> + }
> }
>
> return 0;
> --
> 2.26.2
>