[PATCH v2 2/2] drm/omap: partial workaround for DRA7xx DMM errata i878
Peter Ujfalusi
peter.ujfalusi at ti.com
Fri Mar 23 08:32:03 UTC 2018
On 2018-03-22 15:42, Peter Ujfalusi wrote:
> From: Tomi Valkeinen <tomi.valkeinen at ti.com>
>
> Errata i878 says that MPU should not be used to access RAM and DMM at
> the same time. As it's not possible to prevent MPU accessing RAM, we
> need to access DMM via a proxy.
>
> This patch changes DMM driver to access DMM registers via sDMA. Instead
> of doing a normal readl/writel call to read/write a register, we use
> sDMA to copy 4 bytes from/to the DMM registers.
>
> This patch provides only a partial workaround for i878, as not only DMM
> register reads/writes are affected, but also accesses to the DMM mapped
> buffers (framebuffers, usually).
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
I have failed to add:
Signed-off-by: Peter Ujfalusi <peter.ujfalusi at ti.com>
> ---
> drivers/gpu/drm/omapdrm/omap_dmm_priv.h | 8 ++
> drivers/gpu/drm/omapdrm/omap_dmm_tiler.c | 153 ++++++++++++++++++++++++++++++-
> 2 files changed, 159 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/omapdrm/omap_dmm_priv.h b/drivers/gpu/drm/omapdrm/omap_dmm_priv.h
> index c2785cc98dc9..9ce9d1d7039a 100644
> --- a/drivers/gpu/drm/omapdrm/omap_dmm_priv.h
> +++ b/drivers/gpu/drm/omapdrm/omap_dmm_priv.h
> @@ -155,10 +155,12 @@ struct refill_engine {
>
> struct dmm_platform_data {
> u32 cpu_cache_flags;
> + bool errata_i878_wa;
> };
>
> struct dmm {
> struct device *dev;
> + dma_addr_t phys_base;
> void __iomem *base;
> int irq;
>
> @@ -189,6 +191,12 @@ struct dmm {
> struct list_head alloc_head;
>
> const struct dmm_platform_data *plat_data;
> +
> + bool dmm_workaround;
> + spinlock_t wa_lock;
> + u32 *wa_dma_data;
> + dma_addr_t wa_dma_handle;
> + struct dma_chan *wa_dma_chan;
> };
>
> #endif
> diff --git a/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c b/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c
> index e84871e74615..27c67bc36203 100644
> --- a/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c
> +++ b/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c
> @@ -18,6 +18,7 @@
> #include <linux/completion.h>
> #include <linux/delay.h>
> #include <linux/dma-mapping.h>
> +#include <linux/dmaengine.h>
> #include <linux/errno.h>
> #include <linux/init.h>
> #include <linux/interrupt.h>
> @@ -79,14 +80,138 @@ static const u32 reg[][4] = {
> DMM_PAT_DESCR__2, DMM_PAT_DESCR__3},
> };
>
> +static int dmm_dma_copy(struct dmm *dmm, dma_addr_t src, dma_addr_t dst)
> +{
> + struct dma_device *dma_dev = dmm->wa_dma_chan->device;
> + struct dma_async_tx_descriptor *tx;
> + enum dma_status status;
> + dma_cookie_t cookie;
> +
> + tx = dma_dev->device_prep_dma_memcpy(dmm->wa_dma_chan, dst, src, 4, 0);
> + if (!tx) {
> + dev_err(dmm->dev, "Failed to prepare DMA memcpy\n");
> + return -EIO;
> + }
> +
> + cookie = tx->tx_submit(tx);
> + if (dma_submit_error(cookie)) {
> + dev_err(dmm->dev, "Failed to do DMA tx_submit\n");
> + return -EIO;
> + }
> +
> + dma_async_issue_pending(dmm->wa_dma_chan);
> + status = dma_sync_wait(dmm->wa_dma_chan, cookie);
> + if (status != DMA_COMPLETE)
> + dev_err(dmm->dev, "i878 wa DMA copy failure\n");
> +
> + dmaengine_terminate_all(dmm->wa_dma_chan);
> + return 0;
> +}
> +
> +static u32 dmm_read_wa(struct dmm *dmm, u32 reg)
> +{
> + dma_addr_t src, dst;
> + int r;
> +
> + src = dmm->phys_base + reg;
> + dst = dmm->wa_dma_handle;
> +
> + r = dmm_dma_copy(dmm, src, dst);
> + if (r) {
> + dev_err(dmm->dev, "sDMA read transfer timeout\n");
> + return readl(dmm->base + reg);
> + }
> +
> + /*
> + * As per i878 workaround, the DMA is used to access the DMM registers.
> + * Make sure that the readl is not moved by the compiler or the CPU
> + * earlier than the DMA finished writing the value to memory.
> + */
> + rmb();
> + return readl(dmm->wa_dma_data);
> +}
> +
> +static void dmm_write_wa(struct dmm *dmm, u32 val, u32 reg)
> +{
> + dma_addr_t src, dst;
> + int r;
> +
> + writel(val, dmm->wa_dma_data);
> + /*
> + * As per i878 workaround, the DMA is used to access the DMM registers.
> + * Make sure that the writel is not moved by the compiler or the CPU, so
> + * the data will be in place before we start the DMA to do the actual
> + * register write.
> + */
> + wmb();
> +
> + src = dmm->wa_dma_handle;
> + dst = dmm->phys_base + reg;
> +
> + r = dmm_dma_copy(dmm, src, dst);
> + if (r) {
> + dev_err(dmm->dev, "sDMA write transfer timeout\n");
> + writel(val, dmm->base + reg);
> + }
> +}
> +
> static u32 dmm_read(struct dmm *dmm, u32 reg)
> {
> - return readl(dmm->base + reg);
> + if (dmm->dmm_workaround) {
> + u32 v;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&dmm->wa_lock, flags);
> + v = dmm_read_wa(dmm, reg);
> + spin_unlock_irqrestore(&dmm->wa_lock, flags);
> +
> + return v;
> + } else {
> + return readl(dmm->base + reg);
> + }
> }
>
> static void dmm_write(struct dmm *dmm, u32 val, u32 reg)
> {
> - writel(val, dmm->base + reg);
> + if (dmm->dmm_workaround) {
> + unsigned long flags;
> +
> + spin_lock_irqsave(&dmm->wa_lock, flags);
> + dmm_write_wa(dmm, val, reg);
> + spin_unlock_irqrestore(&dmm->wa_lock, flags);
> + } else {
> + writel(val, dmm->base + reg);
> + }
> +}
> +
> +static int dmm_workaround_init(struct dmm *dmm)
> +{
> + dma_cap_mask_t mask;
> +
> + spin_lock_init(&dmm->wa_lock);
> +
> + dmm->wa_dma_data = dma_alloc_coherent(dmm->dev, sizeof(u32),
> + &dmm->wa_dma_handle, GFP_KERNEL);
> + if (!dmm->wa_dma_data)
> + return -ENOMEM;
> +
> + dma_cap_zero(mask);
> + dma_cap_set(DMA_MEMCPY, mask);
> +
> + dmm->wa_dma_chan = dma_request_channel(mask, NULL, NULL);
> + if (!dmm->wa_dma_chan) {
> + dma_free_coherent(dmm->dev, 4, dmm->wa_dma_data, dmm->wa_dma_handle);
> + return -ENODEV;
> + }
> +
> + return 0;
> +}
> +
> +static void dmm_workaround_uninit(struct dmm *dmm)
> +{
> + dma_release_channel(dmm->wa_dma_chan);
> +
> + dma_free_coherent(dmm->dev, 4, dmm->wa_dma_data, dmm->wa_dma_handle);
> }
>
> /* simple allocator to grab next 16 byte aligned memory from txn */
> @@ -632,6 +757,9 @@ static int omap_dmm_remove(struct platform_device *dev)
> if (omap_dmm->dummy_page)
> __free_page(omap_dmm->dummy_page);
>
> + if (omap_dmm->dmm_workaround)
> + dmm_workaround_uninit(omap_dmm);
> +
> if (omap_dmm->irq > 0)
> free_irq(omap_dmm->irq, omap_dmm);
>
> @@ -680,6 +808,7 @@ static int omap_dmm_probe(struct platform_device *dev)
> goto fail;
> }
>
> + omap_dmm->phys_base = mem->start;
> omap_dmm->base = ioremap(mem->start, SZ_2K);
>
> if (!omap_dmm->base) {
> @@ -695,6 +824,17 @@ static int omap_dmm_probe(struct platform_device *dev)
>
> omap_dmm->dev = &dev->dev;
>
> + if (omap_dmm->plat_data->errata_i878_wa) {
> + if (!dmm_workaround_init(omap_dmm)) {
> + omap_dmm->dmm_workaround = true;
> + dev_info(&dev->dev,
> + "workaround for errata i878 in use\n");
> + } else {
> + dev_warn(&dev->dev,
> + "failed to initialize work-around for i878\n");
> + }
> + }
> +
> hwinfo = dmm_read(omap_dmm, DMM_PAT_HWINFO);
> omap_dmm->num_engines = (hwinfo >> 24) & 0x1F;
> omap_dmm->num_lut = (hwinfo >> 16) & 0x1F;
> @@ -1058,6 +1198,11 @@ static const struct dmm_platform_data dmm_omap5_platform_data = {
> .cpu_cache_flags = OMAP_BO_UNCACHED,
> };
>
> +static const struct dmm_platform_data dmm_dra7_platform_data = {
> + .cpu_cache_flags = OMAP_BO_UNCACHED,
> + .errata_i878_wa = true,
> +};
> +
> static const struct of_device_id dmm_of_match[] = {
> {
> .compatible = "ti,omap4-dmm",
> @@ -1067,6 +1212,10 @@ static const struct of_device_id dmm_of_match[] = {
> .compatible = "ti,omap5-dmm",
> .data = &dmm_omap5_platform_data,
> },
> + {
> + .compatible = "ti,dra7-dmm",
> + .data = &dmm_dra7_platform_data,
> + },
> {},
> };
> #endif
>
- Péter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
More information about the dri-devel
mailing list