Re: [PATCH] remoteproc: imx_dsp_rproc: add custom memory copy implementation for i.MX DSP Cores

Mathieu Poirier
2023-01-26T22:50:22Z

On Wed, Jan 25, 2023 at 01:01:00PM +0200, Iuliana Prodan (OSS) wrote:
> From: Iuliana Prodan <iuliana.prodan@nxp.com>
>
> The IRAM is part of the HiFi DSP.
> According to hardware specification only 32-bits write are allowed
> otherwise we get a Kernel panic.
>
> Therefore add a custom memory copy function to deal with the
> above restriction.
>
> Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>
> ---
> drivers/remoteproc/imx_dsp_rproc.c | 122 ++++++++++++++++++++++++++++-
> 1 file changed, 121 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/remoteproc/imx_dsp_rproc.c b/drivers/remoteproc/imx_dsp_rproc.c
> index 95da1cbefacf..a9991d085494 100644
> --- a/drivers/remoteproc/imx_dsp_rproc.c
> +++ b/drivers/remoteproc/imx_dsp_rproc.c
> @@ -715,6 +715,126 @@ static void imx_dsp_rproc_kick(struct rproc *rproc, int vqid)
> dev_err(dev, "%s: failed (%d, err:%d)\n", __func__, vqid, err);
> }
>
> +/*
> + * Custom memory copy implementation for i.MX DSP Cores
> + *
> + * The IRAM is part of the HiFi DSP.
> + * According to hw specs only 32-bits writes are allowed.
> + */
> +static int imx_dsp_rproc_memcpy(void *dest, const void *src, size_t size)
> +{
> + const u8 *src_byte = src;
> + u32 affected_mask;
> + u32 tmp;
> + int q, r;
> +
> + q = size / 4;
> + r = size % 4;
> +
> + /* __iowrite32_copy use 32bit size values so divide by 4 */
> + __iowrite32_copy(dest, src, q);

The current driver for imx_dsp_rproc does not provide a rproc_da_to_va()
operation, meaning that @is_iomem in rproc_elf_load_segments() can't be true,
forcing a memcpy() operation to be used. And yet above an _iowrite32_copy() is
used...

In the conversation that came out of[1], Daniel Baluta mentions that
read/writes should be done in multiples of 32/64 bit but here a blanket 32 bit
enforcement is done.

> +
> + if (r) {
> + affected_mask = (1 << (8 * r)) - 1;
> +
> + /* first read the 32bit data of dest, then change affected
> + * bytes, and write back to dest.
> + * For unaffected bytes, it should not be changed
> + */
> + tmp = ioread32(dest + q * 4);
> + tmp &= ~affected_mask;
> +
> + tmp |= *(u32 *)(src_byte + q * 4) & affected_mask;
> + iowrite32(tmp, dest + q * 4);
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * imx_dsp_rproc_elf_load_segments() - load firmware segments to memory
> + * @rproc: remote processor which will be booted using these fw segments
> + * @fw: the ELF firmware image
> + *
> + * This function loads the firmware segments to memory, where the remote
> + * processor expects them.
> + *
> + * Return: 0 on success and an appropriate error code otherwise
> + */
> +static int imx_dsp_rproc_elf_load_segments(struct rproc *rproc, const struct firmware *fw)
> +{
> + struct device *dev = &rproc->dev;
> + const void *ehdr, *phdr;
> + int i, ret = 0;
> + u16 phnum;
> + const u8 *elf_data = fw->data;
> + u8 class = fw_elf_get_class(fw);
> + u32 elf_phdr_get_size = elf_size_of_phdr(class);
> +
> + ehdr = elf_data;
> + phnum = elf_hdr_get_e_phnum(class, ehdr);
> + phdr = elf_data + elf_hdr_get_e_phoff(class, ehdr);
> +
> + /* go through the available ELF segments */
> + for (i = 0; i < phnum; i++, phdr += elf_phdr_get_size) {
> + u64 da = elf_phdr_get_p_paddr(class, phdr);
> + u64 memsz = elf_phdr_get_p_memsz(class, phdr);
> + u64 filesz = elf_phdr_get_p_filesz(class, phdr);
> + u64 offset = elf_phdr_get_p_offset(class, phdr);
> + u32 type = elf_phdr_get_p_type(class, phdr);
> + bool is_iomem = false;
> + void *ptr;
> +
> + if (type != PT_LOAD || !memsz)
> + continue;
> +
> + dev_dbg(dev, "phdr: type %d da 0x%llx memsz 0x%llx filesz 0x%llx\n",
> + type, da, memsz, filesz);
> +
> + if (filesz > memsz) {
> + dev_err(dev, "bad phdr filesz 0x%llx memsz 0x%llx\n",
> + filesz, memsz);
> + ret = -EINVAL;
> + break;
> + }
> +
> + if (offset + filesz > fw->size) {
> + dev_err(dev, "truncated fw: need 0x%llx avail 0x%zx\n",
> + offset + filesz, fw->size);
> + ret = -EINVAL;
> + break;
> + }
> +
> + if (!rproc_u64_fit_in_size_t(memsz)) {
> + dev_err(dev, "size (%llx) does not fit in size_t type\n",
> + memsz);
> + ret = -EOVERFLOW;
> + break;
> + }
> +
> + /* grab the kernel address for this device address */
> + ptr = rproc_da_to_va(rproc, da, memsz, &is_iomem);
> + if (!ptr) {
> + dev_err(dev, "bad phdr da 0x%llx mem 0x%llx\n", da,
> + memsz);
> + ret = -EINVAL;
> + break;
> + }
> +
> + /* put the segment where the remote processor expects it */
> + if (filesz) {
> + ret = imx_dsp_rproc_memcpy(ptr, elf_data + offset, filesz);
> + if (ret) {
> + dev_err(dev, "memory copy failed for da 0x%llx memsz 0x%llx\n",
> + da, memsz);
> + break;
> + }
> + }

This patchset from last year[1] goes to great length to avoid using a driver
specific function and now you are trying to bring that back... So how was it
working before and why are things broken now? Moreover, function
rproc_elf_load_segments() deals with situations where the memory slot is bigger
than the file size[2], which is omitted here.

Thanks,
Mathieu

[1]. https://lore.kernel.org/linux-arm-kernel/20220323064944.1351923-1-peng.fan@oss.nxp.com/
[2]. https://elixir.bootlin.com/linux/v6.2-rc5/source/drivers/remoteproc/remoteproc_elf_loader.c#L221

> + }
> +
> + return ret;
> +}
> +
> static int imx_dsp_rproc_parse_fw(struct rproc *rproc, const struct firmware *fw)
> {
> if (rproc_elf_load_rsc_table(rproc, fw))
> @@ -729,7 +849,7 @@ static const struct rproc_ops imx_dsp_rproc_ops = {
> .start = imx_dsp_rproc_start,
> .stop = imx_dsp_rproc_stop,
> .kick = imx_dsp_rproc_kick,
> - .load = rproc_elf_load_segments,
> + .load = imx_dsp_rproc_elf_load_segments,
> .parse_fw = imx_dsp_rproc_parse_fw,
> .sanity_check = rproc_elf_sanity_check,
> .get_boot_addr = rproc_elf_get_boot_addr,
> --
> 2.17.1