lkml.org 
[lkml]   [2019]   [May]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/3] mmc: meson-gx: add ddr-access-quirk
From
Date
On 15/05/2019 23:18, Martin Blumenstingl wrote:
> Hi Neil,
>
> On Wed, May 15, 2019 at 2:45 PM Neil Armstrong <narmstrong@baylibre.com> wrote:
>>
>> 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,
> so writing bounce_dma_addr to SD_EMMC_CMD_DAT is needed to make it work?
>
>> and we need the logical address to memcpy() in the buffer.
> as far as I understand that is what we use the "bounce_buf" member
> for, but I don't see why we need "bounce_dma_addr"

Sorry I don't understand these questions, I haven't changed the
bounce buffer behavior here, I only make it use a local SRAM buffer
instead of an dma_alloc_coherent() allocated buffer.

Having bounce_buf_size/bounce_buf/bounce_dma_addr is still necessary like
an allocated 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.
> I wasn't clear in my last email, I meant this error case:
> err_bounce_buf:
> dma_free_coherent(host->dev, host->bounce_buf_size, ...
> when host->ddr_access_quirk is true then you skip the
> dma_alloc_coherent call for bounce_buf

Oh, ok, yes, I'll add it.

Neil

>
>
> Martin
>

\
 
 \ /
  Last update: 2019-05-16 11:11    [W:0.052 / U:32.332 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site