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SubjectRe: [PATCH 2/3] mmc: meson-gx: add ddr-access-quirk
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On 14/05/2019 19:58, Martin Blumenstingl wrote:
> Hi Neil,
>
> On Mon, May 13, 2019 at 11:16 AM Neil Armstrong <narmstrong@baylibre.com> wrote:
> [...]
>> @@ -1158,15 +1183,27 @@ static int meson_mmc_probe(struct platform_device *pdev)
>> */
>> mmc->caps2 &= ~MMC_CAP2_HS400;
>>
>> - /* data bounce buffer */
>> - host->bounce_buf_size = mmc->max_req_size;
>> - host->bounce_buf =
>> - dma_alloc_coherent(host->dev, host->bounce_buf_size,
>> - &host->bounce_dma_addr, GFP_KERNEL);
>> - if (host->bounce_buf == NULL) {
>> - dev_err(host->dev, "Unable to map allocate DMA bounce buffer.\n");
>> - ret = -ENOMEM;
>> - goto err_free_irq;
>> + if (host->ddr_access_quirk) {
>> + /*
>> + * The MMC Controller embeds 1,5KiB of internal SRAM
>> + * that can be used to be used as bounce buffer.
>> + * In the case of the G12A SDIO controller, use these
>> + * instead of the DDR memory
>> + */
>> + host->bounce_buf_size = SD_EMMC_SRAM_DATA_BUF_LEN;
>> + host->bounce_buf = host->regs + SD_EMMC_SRAM_DATA_BUF_OFF;
>> + host->bounce_dma_addr = res->start + SD_EMMC_SRAM_DATA_BUF_OFF;
> I'm curious: why do you need to set bounce_dma_addr in this case?

We still need the physical bounce buffer address since we write in the registers,
and we need the logical address to memcpy() in the buffer.

>
>> + } else {
>> + /* data bounce buffer */
>> + host->bounce_buf_size = mmc->max_req_size;
>> + host->bounce_buf =
>> + dma_alloc_coherent(host->dev, host->bounce_buf_size,
>> + &host->bounce_dma_addr, GFP_KERNEL);
>> + if (host->bounce_buf == NULL) {
>> + dev_err(host->dev, "Unable to map allocate DMA bounce buffer.\n");
>> + ret = -ENOMEM;
>> + goto err_free_irq;
>> + }
>> }
>>
>> host->descs = dma_alloc_coherent(host->dev, SD_EMMC_DESC_BUF_LEN,
> if host->descs cannot be allocated then you need to conditionally skip
> dma_free_coherent for the bounce buffer in the goto err_bounce_buf
> case a few lines below (just like you did in meson_mmc_remove)

It can be allocated, it's only useless. I can skip it but I don't want
to break any logic in the driver.

>
>
> Martin
>

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