[PATCH 1/2] mmc: atmel-mci: DMA can be used with other controller
From: ludovic.desroches <hidden>
Date: 2012-08-28 13:25:58
Also in:
linux-mmc
Hi Hein, Thanks for your investigation about the MCI issue with AVR chips. Le 08/26/2012 10:20 PM, Hein Tibosch a ?crit :
After the latest changes to atmel-mci, it could not be used with DMA on the AVR32 platform. This patch will allow to use DMA again and it will avoid access to MCI register ATMCI_DMA.
I think you should add more details about the issue: Even if the IP version is lower than v3xx and doesn't have the DMA configuration register, DMA transfers can be used with a different controller than the Atmel AHB DMA one. For instance, some AVR chips use the Synopsys DesignWare AHB DMA controller.
Signed-off-by: Hein Tibosch <redacted>
Some comments below...
quoted hunk ↗ jump to hunk
--- drivers/mmc/host/atmel-mci.c | 21 +++++++++------------ 1 files changed, 9 insertions(+), 12 deletions(-)diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c index f2c115e..66e9fdc 100644 --- a/drivers/mmc/host/atmel-mci.c +++ b/drivers/mmc/host/atmel-mci.c@@ -71,7 +71,7 @@ enum atmci_pdc_buf { }; struct atmel_mci_caps { - bool has_dma; + bool has_dma_conf_reg; bool has_pdc; bool has_cfg_reg; bool has_cstor_reg;@@ -411,7 +411,7 @@ static int atmci_regs_show(struct seq_file *s, void *v) atmci_show_status_reg(s, "SR", buf[ATMCI_SR / 4]); atmci_show_status_reg(s, "IMR", buf[ATMCI_IMR / 4]); - if (host->caps.has_dma) { + if (host->caps.has_dma_conf_reg) { u32 val; val = buf[ATMCI_DMA / 4];@@ -767,7 +767,7 @@ static void atmci_dma_complete(void *arg) dev_vdbg(&host->pdev->dev, "DMA complete\n"); - if (host->caps.has_dma) + if (host->caps.has_dma_conf_reg) /* Disable DMA hardware handshaking on MCI */ atmci_writel(host, ATMCI_DMA, atmci_readl(host, ATMCI_DMA) & ~ATMCI_DMAEN);@@ -954,7 +954,9 @@ atmci_prepare_data_dma(struct atmel_mci *host, struct mmc_data *data) maxburst = atmci_convert_chksize(host->dma_conf.dst_maxburst); } - atmci_writel(host, ATMCI_DMA, ATMCI_DMA_CHKSIZE(maxburst) | ATMCI_DMAEN); + if (host->caps.has_dma_conf_reg) + atmci_writel(host, ATMCI_DMA, ATMCI_DMA_CHKSIZE(maxburst) | + ATMCI_DMAEN); sglen = dma_map_sg(chan->device->dev, data->sg, data->sg_len, direction);@@ -2202,7 +2204,7 @@ static void __init atmci_get_cap(struct atmel_mci *host) dev_info(&host->pdev->dev, "version: 0x%x\n", version); - host->caps.has_dma = 0; + host->caps.has_dma_conf_reg = 0; host->caps.has_pdc = 1; host->caps.has_cfg_reg = 0; host->caps.has_cstor_reg = 0;@@ -2219,12 +2221,7 @@ static void __init atmci_get_cap(struct atmel_mci *host) host->caps.has_odd_clk_div = 1; case 0x400: case 0x300: -#ifdef CONFIG_AT_HDMAC - host->caps.has_dma = 1; -#else - dev_info(&host->pdev->dev, - "has dma capability but dma engine is not selected, then use pio\n"); -#endif + host->caps.has_dma_conf_reg = 1; host->caps.has_pdc = 0; host->caps.has_cfg_reg = 1; host->caps.has_cstor_reg = 1;@@ -2298,7 +2295,7 @@ static int __init atmci_probe(struct platform_device *pdev) /* Get MCI capabilities and set operations according to it */ atmci_get_cap(host); - if (host->caps.has_dma && atmci_configure_dma(host)) { + if (atmci_configure_dma(host)) { host->prepare_data = &atmci_prepare_data_dma; host->submit_data = &atmci_submit_data_dma; host->stop_transfer = &atmci_stop_transfer_dma;
I have tested this patch on at91sam9m10g45, at91sam9g10 and at91sam9261. For chips without MCI support for Atmel AHB DMA, removing the host->caps.has_dma test involves to use pdata->dma_slave with more caution to avoid some NULL pointer dereferences
@@ -2168,16 +2168,21 @@ static bool atmci_configure_dma(struct atmel_mci *host)
return false;
pdata = host->pdev->dev.platform_data;
+ if (!pdata)
+ return false;
- if (pdata && find_slave_dev(pdata->dma_slave)) {
+ if (pdata->dma_slave && find_slave_dev(pdata->dma_slave)) {
dma_cap_mask_t mask;
Regards
Ludovic