Re: [PATCH 1/7] mmc: sdhci: add support for using external DMA devices

Faiz Abbas
2019-01-29T11:53:37Z

Chunyan,

On 28/01/19 5:16 PM, Chunyan Zhang wrote:
> On Mon, 28 Jan 2019 at 18:40, Faiz Abbas <faiz_abbas@ti.com> wrote:
>>
>> Hi,
>>
>> On 28/01/19 3:50 PM, Chunyan Zhang wrote:
>>> On Thu, 24 Jan 2019 at 19:41, Adrian Hunter <adrian.hunter@intel.com> wrote:
>>>>
>>>> On 11/01/19 1:08 PM, Faiz Abbas wrote:
>>>>> From: Chunyan Zhang <zhang.chunyan@linaro.org>
>>>>>
>>>>> Some standard SD host controllers can support both external dma
>>>>> controllers as well as ADMA/SDMA in which the SD host controller
>>>>> acts as DMA master. TI's omap controller is the case as an example.
>>>>>
>>>>> Currently the generic SDHCI code supports ADMA/SDMA integrated in
>>>>> the host controller but does not have any support for external DMA
>>>>> controllers implemented using dmaengine, meaning that custom code is
>>>>> needed for any systems that use an external DMA controller with SDHCI.
>>>>>
>>>>> Fixes by Faiz Abbas <faiz_abbas@ti.com>:
>>>>> 1. Map scatterlists before dmaengine_prep_slave_sg()
>>>>> 2. Use dma_async() functions inside of the send_command() path and
>>>>> synchronize once at the start of each request.
>>>>
>>>> Sorry for the slow reply, but I do have some concerns. Please see the comments.
>>>>
>>>>>
>>>>> Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
>>>>> Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
>>>>> ---
>>>>> drivers/mmc/host/Kconfig | 3 +
>>>>> drivers/mmc/host/sdhci.c | 266 ++++++++++++++++++++++++++++++++++++++-
>>>>> drivers/mmc/host/sdhci.h | 8 ++
>>>>> 3 files changed, 273 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
>>>>> index e26b8145efb3..333292e8ecdd 100644
>>>>> --- a/drivers/mmc/host/Kconfig
>>>>> +++ b/drivers/mmc/host/Kconfig
>>>>> @@ -999,3 +999,6 @@ config MMC_SDHCI_AM654
>>>>> If you have a controller with this interface, say Y or M here.
>>>>>
>>>>> If unsure, say N.
>>>>> +
>>>>> +config MMC_SDHCI_EXTERNAL_DMA
>>>>> + bool
>>>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>>>> index a22e11a65658..4a9044c06e21 100644
>>>>> --- a/drivers/mmc/host/sdhci.c
>>>>> +++ b/drivers/mmc/host/sdhci.c
>>>>> @@ -14,6 +14,7 @@
>>>>> */
>>>>>
>>>>> #include <linux/delay.h>
>>>>> +#include <linux/dmaengine.h>
>>>>> #include <linux/ktime.h>
>>>>> #include <linux/highmem.h>
>>>>> #include <linux/io.h>
>>>>> @@ -1118,6 +1119,226 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_command *cmd)
>>>>> }
>>>>> }
>>>>>
>>>>> +#if IS_ENABLED(CONFIG_MMC_SDHCI_EXTERNAL_DMA)
>>>>> +static int sdhci_external_dma_init(struct sdhci_host *host)
>>>>> +{
>>>>> + int ret = 0;
>>>>> + struct mmc_host *mmc = host->mmc;
>>>>> +
>>>>> + host->tx_chan = dma_request_chan(mmc->parent, "tx");
>>>>> + if (IS_ERR(host->tx_chan)) {
>>>>> + ret = PTR_ERR(host->tx_chan);
>>>>> + if (ret != -EPROBE_DEFER)
>>>>> + pr_warn("Failed to request TX DMA channel.\n");
>>>>> + host->tx_chan = NULL;
>>>>> + return ret;
>>>>> + }
>>>>> +
>>>>> + host->rx_chan = dma_request_chan(mmc->parent, "rx");
>>>>> + if (IS_ERR(host->rx_chan)) {
>>>>> + if (host->tx_chan) {
>>>>> + dma_release_channel(host->tx_chan);
>>>>> + host->tx_chan = NULL;
>>>>> + }
>>>>> +
>>>>> + ret = PTR_ERR(host->rx_chan);
>>>>> + if (ret != -EPROBE_DEFER)
>>>>> + pr_warn("Failed to request RX DMA channel.\n");
>>>>> + host->rx_chan = NULL;
>>>>> + }
>>>>> +
>>>>> + return ret;
>>>>> +}
>>>>> +
>>>>> +static inline struct dma_chan *
>>>>> +sdhci_external_dma_channel(struct sdhci_host *host, struct mmc_data *data)
>>>>> +{
>>>>> + return data->flags & MMC_DATA_WRITE ? host->tx_chan : host->rx_chan;
>>>>> +}
>>>>> +
>>>>> +static int sdhci_external_dma_setup(struct sdhci_host *host,
>>>>> + struct mmc_command *cmd)
>>>>> +{
>>>>> + int ret, i;
>>>>> + struct dma_async_tx_descriptor *desc;
>>>>> + struct mmc_data *data = cmd->data;
>>>>> + struct dma_chan *chan;
>>>>> + struct dma_slave_config cfg;
>>>>> + dma_cookie_t cookie;
>>>>> + int sg_cnt;
>>>>> +
>>>>> + if (!host->mapbase)
>>>>> + return -EINVAL;
>>>>> +
>>>>> + cfg.src_addr = host->mapbase + SDHCI_BUFFER;
>>>>> + cfg.dst_addr = host->mapbase + SDHCI_BUFFER;
>>>>> + cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
>>>>> + cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
>>>>> + cfg.src_maxburst = data->blksz / 4;
>>>>> + cfg.dst_maxburst = data->blksz / 4;
>>>>> +
>>>>> + /* Sanity check: all the SG entries must be aligned by block size. */
>>>>> + for (i = 0; i < data->sg_len; i++) {
>>>>> + if ((data->sg + i)->length % data->blksz)
>>>>> + return -EINVAL;
>>>>> + }
>>>>> +
>>>>> + chan = sdhci_external_dma_channel(host, data);
>>>>> +
>>>>> + ret = dmaengine_slave_config(chan, &cfg);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + sg_cnt = sdhci_pre_dma_transfer(host, data, COOKIE_MAPPED);
>>>>> + if (sg_cnt <= 0)
>>>>> + return -EINVAL;
>>>>> +
>>>>> + desc = dmaengine_prep_slave_sg(chan, data->sg, data->sg_len,
>>>>> + mmc_get_dma_dir(data),
>>>>> + DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
>>>>> + if (!desc)
>>>>> + return -EINVAL;
>>>>> +
>>>>> + desc->callback = NULL;
>>>>> + desc->callback_param = NULL;
>>>>> +
>>>>> + cookie = dmaengine_submit(desc);
>>>>> + if (cookie < 0)
>>>>> + ret = cookie;
>>>>> +
>>>>> + return ret;
>>>>> +}
>>>>> +
>>>>> +static void sdhci_external_dma_release(struct sdhci_host *host)
>>>>> +{
>>>>> + if (host->tx_chan) {
>>>>> + dma_release_channel(host->tx_chan);
>>>>> + host->tx_chan = NULL;
>>>>> + }
>>>>> +
>>>>> + if (host->rx_chan) {
>>>>> + dma_release_channel(host->rx_chan);
>>>>> + host->rx_chan = NULL;
>>>>> + }
>>>>> +
>>>>> + sdhci_switch_external_dma(host, false);
>>>>> +}
>>>>> +
>>>>> +static int __sdhci_external_dma_prepare_data(struct sdhci_host *host,
>>>>> + struct mmc_command *cmd)
>>>>> +{
>>>>> + struct mmc_data *data = cmd->data;
>>>>> +
>>>>> + host->data_timeout = 0;
>>>>> +
>>>>> + if (sdhci_data_line_cmd(cmd))
>>>>> + sdhci_set_timeout(host, cmd);
>>>>> +
>>>>> + WARN_ON(host->data);
>>>>> +
>>>>> + /* Sanity checks */
>>>>> + WARN_ON(data->blksz * data->blocks > 524288);
>>>>> + WARN_ON(data->blksz > host->mmc->max_blk_size);
>>>>> + WARN_ON(data->blocks > 65535);
>>>>> +
>>>>> + host->flags |= SDHCI_REQ_USE_DMA;
>>>>> + host->data = data;
>>>>> + host->data_early = 0;
>>>>> + host->data->bytes_xfered = 0;
>>>>> +
>>>>> + sdhci_set_transfer_irqs(host);
>>>>> +
>>>>> + /*
>>>>> + * For Version 4.10 onwards, if v4 mode is enabled, 32-bit Block Count
>>>>> + * can be supported, in that case 16-bit block count register must be 0.
>>>>> + */
>>>>> + if (host->version >= SDHCI_SPEC_410 && host->v4_mode &&
>>>>> + (host->quirks2 & SDHCI_QUIRK2_USE_32BIT_BLK_CNT)) {
>>>>> + if (sdhci_readw(host, SDHCI_BLOCK_COUNT))
>>>>> + sdhci_writew(host, 0, SDHCI_BLOCK_COUNT);
>>>>> + sdhci_writew(host, data->blocks, SDHCI_32BIT_BLK_CNT);
>>>>> + } else {
>>>>> + sdhci_writew(host, data->blocks, SDHCI_BLOCK_COUNT);
>>>>> + }
>>>>
>>>> It is probably worth factoring out the code that is shared with
>>>> sdhci_prepare_data() where possible.
>>>>
>>>>> +
>>>>> + return 0;
>>>>> +}
>>>>> +
>>>>> +static void sdhci_external_dma_prepare_data(struct sdhci_host *host,
>>>>> + struct mmc_command *cmd)
>>>>> +{
>>>>> + struct mmc_data *data = cmd->data;
>>>>> +
>>>>> + if (!data)
>>>>> + return;
>>>>
>>>> Even in the !data case, we still need to set up a timeout for commands with
>>>> busy waiting. I suggest checking the !data case before calling
>>>> sdhci_external_dma_prepare_data()
>>>
>>> Ok.
>>>
>>>>
>>>>> +
>>>>> + if (sdhci_external_dma_setup(host, cmd) ||
>>>>> + __sdhci_external_dma_prepare_data(host, cmd)) {
>>>>> + sdhci_external_dma_release(host);
>>>>> + pr_err("%s: Cannot use external DMA, switch to the DMA/PIO which standard SDHCI provides.\n",
>>>>> + mmc_hostname(host->mmc));
>>>>> + sdhci_prepare_data(host, cmd);
>>>>> + }
>>>>> +}
>>>>> +
>>>>> +static void sdhci_external_dma_pre_transfer(struct sdhci_host *host,
>>>>> + struct mmc_command *cmd)
>>>>> +{
>>>>> + struct dma_chan *chan;
>>>>> +
>>>>> + if (!cmd->data || cmd->opcode == MMC_SET_BLOCK_COUNT)
>>>>
>>>> MMC_SET_BLOCK_COUNT never has cmd->data and so does not need to be checked.
>>>
>>> Ok.
>>>
>>>>
>>>>> + return;
>>>>> +
>>>>> + sdhci_writew(host, cmd->data->blksz, SDHCI_BLOCK_SIZE);
>>>>
>>>> Block size is set in __sdhci_external_dma_prepare_data() so does it need to
>>>> be set here also.
>>>
>>> Ok.
>>
>> That is BLOCK_COUNT. This is BLOCK_SIZE.
>>
>>>
>>>>
>>>>> + chan = sdhci_external_dma_channel(host, cmd->data);
>>>>> + if (chan)
>>>>> + dma_async_issue_pending(chan);
>>>>> +}
>>>>> +
>>>>> +static int sdhci_external_dma_cleanup(struct sdhci_host *host,
>>>>> + struct mmc_data *data)
>>>>
>>>> Please align parameters with open parenthesis
>>>>
>>>>> +{
>>>>> + struct dma_chan *chan = sdhci_external_dma_channel(host, data);
>>>>> + int ret = 0;
>>>>> +
>>>>> + if (chan)
>>>>> + ret = dmaengine_terminate_async(chan);
>>>>> +
>>>>> + return ret;
>>>>> +}
>>>>> +#else
>>>>> +static int sdhci_external_dma_init(struct sdhci_host *host)
>>>>> +{
>>>>> + return -EOPNOTSUPP;
>>>>> +}
>>>>> +
>>>>> +static void sdhci_external_dma_release(struct sdhci_host *host)
>>>>> +{}
>>>>> +
>>>>> +static void sdhci_external_dma_prepare_data(struct sdhci_host *host,
>>>>> + struct mmc_command *cmd)
>>>>> +{
>>>>> + /* If MMC_SDHCI_EXTERNAL_DMA not supported, PIO will be used */
>>>>> + sdhci_prepare_data(host, cmd);
>>>>> +}
>>>>> +
>>>>> +static void sdhci_external_dma_pre_transfer(struct sdhci_host *host,
>>>>> + struct mmc_command *cmd)
>>>>> +{}
>>>>> +
>>>>> +static int sdhci_external_dma_cleanup(struct sdhci_host *host,
>>>>> + struct mmc_data *data)
>>>>
>>>> Please align parameters with open parenthesis
>>>>
>>>>> +{
>>>>> + return 0;
>>>>> +}
>>>>> +#endif
>>>>> +
>>>>> +void sdhci_switch_external_dma(struct sdhci_host *host, bool en)
>>>>> +{
>>>>> + host->use_external_dma = en;
>>>>> +}
>>>>> +EXPORT_SYMBOL_GPL(sdhci_switch_external_dma);
>>>>> +
>>>>> static inline bool sdhci_auto_cmd12(struct sdhci_host *host,
>>>>> struct mmc_request *mrq)
>>>>> {
>>>>> @@ -1374,7 +1595,10 @@ void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
>>>>> host->data_cmd = cmd;
>>>>> }
>>>>>
>>>>> - sdhci_prepare_data(host, cmd);
>>>>> + if (host->use_external_dma)
>>>>
>>>> As mentioned above wrt sdhci_external_dma_prepare_data():
>>>>
>>>> if (host->use_external_dma && cmd->data)
>>>>
>>>
>>> Maybe we should move checking the !data case out of both
>>> _prepare_data, and add it to sdhci_send_command() before calling
>>> _prepare_data(), that's saying we can do set up a timeout in
>>> sdhci_send_command().
>>
>> Lets just factor out everything in common as Adrian said. The !data,
>> BLOCK_COUNT writes and busy waiting.
>
> Ok, and also BLOCK_SIZE which can be set in _prepare_data().
>
>>
>>>
>>>>> + sdhci_external_dma_prepare_data(host, cmd);
>>>>> + else
>>>>> + sdhci_prepare_data(host, cmd);
>>>>>
>>>>> sdhci_writel(host, cmd->arg, SDHCI_ARGUMENT);
>>>>>
>>>>> @@ -1416,6 +1640,9 @@ void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
>>>>> timeout += 10 * HZ;
>>>>> sdhci_mod_timer(host, cmd->mrq, timeout);
>>>>>
>>>>> + if (host->use_external_dma)
>>>>> + sdhci_external_dma_pre_transfer(host, cmd);
>>>>
>>>> Why is sdhci_external_dma_pre_transfer() needed here - couldn't it be done
>>>> in sdhci_external_dma_prepare_data()?
>>>>
>>>
>>> I'm not sure dma_async_issue_pending() can be done so early in
>>> sdhci_external_dma_prepare_data().
>>>
>>>>> +
>>>>> sdhci_writew(host, SDHCI_MAKE_CMD(cmd->opcode, flags), SDHCI_COMMAND);
>>>>> }
>>>>> EXPORT_SYMBOL_GPL(sdhci_send_command);
>>>>> @@ -1781,6 +2008,11 @@ void sdhci_request(struct mmc_host *mmc, struct mmc_request *mrq)
>>>>>
>>>>> sdhci_led_activate(host);
>>>>>
>>>>> + if (host->use_external_dma && mrq->data) {
>>>>> + struct dma_chan *chan = sdhci_external_dma_channel(host,
>>>>> + mrq->data);
>>>>
>>>> sdhci_external_dma_channel is not declared if
>>>> !IS_ENABLED(CONFIG_MMC_SDHCI_EXTERNAL_DMA)
>>>
>>> Ok, I guess this can be moved to sdhci_external_dma_prepare_data().
>>
>> No. We have to synchronize from a guaranteed non-atomic context. Maybe
>> add another empty sdhci_external_dma_channel definition in the #else part?
>>
>>>
>>>>
>>>>> + dmaengine_synchronize(chan);
>>>>
>>>> So this is to cover for using dmaengine_terminate_async()?
>>
>> Yes.
>>
>>>
>>> Ok.
>>>
>>>>
>>>>> + }
>>>>> /*
>>>>> * Ensure we don't send the STOP for non-SET_BLOCK_COUNTED
>>>>> * requests if Auto-CMD12 is enabled.
>>>>> @@ -2658,6 +2890,8 @@ static bool sdhci_request_done(struct sdhci_host *host)
>>>>> dma_unmap_sg(mmc_dev(host->mmc), data->sg,
>>>>> data->sg_len,
>>>>> mmc_get_dma_dir(data));
>>>>> + if (host->use_external_dma)
>>>>> + sdhci_external_dma_cleanup(host, data);
>>>>
>>>> Is sdhci_external_dma_cleanup() only needed in the error case?
>>>>
>>>> The DMA must be stopped before the memory is unmapped and potentially freed.
>>>>
>>>> Isn't the DMA cleanup also needed in the bounce buffer case?
>>>>
>>>> Isn't the DMA cleanup also needed in the COOKIE_PRE_MAPPED case?
>>>>
>>>> dmaengine_terminate_async() doesn't stop the DMA but
>>>> dmaengine_terminate_sync() is not atomic, which looks like a problem.
>>>>
>>>> Perhaps you look at scheduling some work for the external dma error case
>>>> instead of calling __sdhci_finish_mrq()? Then the work can do the
>>>> dmaengine_terminate_sync() and call __sdhci_finish_mrq().
>>>
>>> Ok, I will look at these issues.
>>>
>>>>
>>>>> }
>>>>> data->host_cookie = COOKIE_UNMAPPED;
>>>>> }
>>>>> @@ -3692,12 +3926,15 @@ int sdhci_setup_host(struct sdhci_host *host)
>>>>> mmc_hostname(mmc), host->version);
>>>>> }
>>>>>
>>>>> - if (host->quirks & SDHCI_QUIRK_FORCE_DMA)
>>>>> + if (host->quirks & SDHCI_QUIRK_FORCE_DMA) {
>>>>> host->flags |= SDHCI_USE_SDMA;
>>>>> - else if (!(host->caps & SDHCI_CAN_DO_SDMA))
>>>>> + } else if (!(host->caps & SDHCI_CAN_DO_SDMA)) {
>>>>> DBG("Controller doesn't have SDMA capability\n");
>>>>> - else
>>>>> + } else if (host->use_external_dma) {
>>>>> + /* Using dma-names to detect external dma capability */
>>>>> + } else {
>>>>> host->flags |= SDHCI_USE_SDMA;
>>>>> + }
>>>>
>>>> These if-statements are about setting SDHCI_USE_SDMA but why is a change
>>>> needed for the host->use_external_dma case?
>>>
>>> Yes, this is not needed, otherwise the controller cannot switch back
>>> to SDMA if it is supported in the controller.
>>
>> The else case means that the host always uses SDMA. Needed to make sure
>> this doesn't happen in the external_dma case. Its not SDHCI_CAN_DO_SDMA,
>> its SDHCI_USE_SDMA.
>>
>>>
>>>>
>>>>>
>>>>> if ((host->quirks & SDHCI_QUIRK_BROKEN_DMA) &&
>>>>> (host->flags & SDHCI_USE_SDMA)) {
>>>>> @@ -3785,6 +4022,19 @@ int sdhci_setup_host(struct sdhci_host *host)
>>>>> }
>>>>> }
>>>>>
>>>>> + if (host->use_external_dma) {
>>>>> + ret = sdhci_external_dma_init(host);
>>>>> + if (ret == -EPROBE_DEFER)
>>>>> + goto unreg;
>>>>> +
>>>>> + /*
>>>>> + * Fall back to use the DMA/PIO integrated in standard SDHCI
>>>>> + * instead of external DMA devices.
>>>>> + */
>>>>> + if (ret)
>>>>> + sdhci_switch_external_dma(host, false);
>>>>> + }
>>>>> +
>>>>> /*
>>>>> * If we use DMA, then it's up to the caller to set the DMA
>>>>> * mask, but PIO does not need the hw shim so we set a new
>>>>> @@ -4201,6 +4451,10 @@ void sdhci_cleanup_host(struct sdhci_host *host)
>>>>> dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz +
>>>>> host->adma_table_sz, host->align_buffer,
>>>>> host->align_addr);
>>>>> +
>>>>> + if (host->use_external_dma)
>>>>> + sdhci_external_dma_release(host);
>>>>> +
>>>>> host->adma_table = NULL;
>>>>> host->align_buffer = NULL;
>>>>> }
>>>>> @@ -4247,6 +4501,7 @@ int __sdhci_add_host(struct sdhci_host *host)
>>>>>
>>>>> pr_info("%s: SDHCI controller on %s [%s] using %s\n",
>>>>> mmc_hostname(mmc), host->hw_name, dev_name(mmc_dev(mmc)),
>>>>> + host->use_external_dma ? "External DMA" :
>>>>> (host->flags & SDHCI_USE_ADMA) ?
>>>>> (host->flags & SDHCI_USE_64_BIT_DMA) ? "ADMA 64-bit" : "ADMA" :
>>>>> (host->flags & SDHCI_USE_SDMA) ? "DMA" : "PIO");
>>>>> @@ -4335,6 +4590,9 @@ void sdhci_remove_host(struct sdhci_host *host, int dead)
>>>>> host->adma_table_sz, host->align_buffer,
>>>>> host->align_addr);
>>>>>
>>>>> + if (host->use_external_dma)
>>>>> + sdhci_external_dma_release(host);
>>>>> +
>>>>> host->adma_table = NULL;
>>>>> host->align_buffer = NULL;
>>>>> }
>>>>> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
>>>>> index 6cc9a3c2ac66..7a52823ebef4 100644
>>>>> --- a/drivers/mmc/host/sdhci.h
>>>>> +++ b/drivers/mmc/host/sdhci.h
>>>>> @@ -482,6 +482,7 @@ struct sdhci_host {
>>>>>
>>>>> int irq; /* Device IRQ */
>>>>> void __iomem *ioaddr; /* Mapped address */
>>>>> + phys_addr_t mapbase; /* physical address base */
>>>>> char *bounce_buffer; /* For packing SDMA reads/writes */
>>>>> dma_addr_t bounce_addr;
>>>>> unsigned int bounce_buffer_size;
>>>>> @@ -531,6 +532,7 @@ struct sdhci_host {
>>>>> bool pending_reset; /* Cmd/data reset is pending */
>>>>> bool irq_wake_enabled; /* IRQ wakeup is enabled */
>>>>> bool v4_mode; /* Host Version 4 Enable */
>>>>> + bool use_external_dma; /* Host selects to use external DMA */
>>>>
>>>> Please align /**/ with above i.e. use tab
>>
>> Will fix.
>
> Do you need me to address these comments and then send you a patch or
> you'd like to do instead?
>

This would be much appreciated. Would you be able to work on it this
week? I would like to send a v2 by Friday.

Thanks,
Faiz