On Thu, Nov 21, 2024 at 06:31:34PM +0530, Jyothi Kumar Seerapu wrote:
> I2C functionality has dependencies on the GPI driver.
> Ensure that the GPI driver is enabled when using the I2C
> driver functionality.
> Therefore, update the I2C GENI driver to depend on the GPI driver.
>
> Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu(a)quicinc.com>
> ---
> v2 -> v3:
> - Moved this change to patch3.
> - Updated commit description.
>
> v1 -> v2:
> - This patch is added in v2 to address the kernel test robot
> reported compilation error.
> ERROR: modpost: "gpi_multi_desc_process" [drivers/i2c/busses/i2c-qcom-geni.ko] undefined!
>
> drivers/i2c/busses/Kconfig | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 0aa948014008..87634a682855 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -1049,6 +1049,7 @@ config I2C_QCOM_GENI
> tristate "Qualcomm Technologies Inc.'s GENI based I2C controller"
> depends on ARCH_QCOM || COMPILE_TEST
> depends on QCOM_GENI_SE
> + depends on QCOM_GPI_DMA
So... without this change the previous patch is broken, which is a
no-go. And anyway, adding dependency onto a particular DMA driver is a
bad idea. Please make use of the DMA API instead.
> help
> This driver supports GENI serial engine based I2C controller in
> master mode on the Qualcomm Technologies Inc.'s SoCs. If you say
> --
> 2.17.1
>
--
With best wishes
Dmitry
On Mon, Nov 18, 2024 at 1:15 AM Tvrtko Ursulin <tursulin(a)ursulin.net> wrote:
>
>
> On 17/11/2024 17:03, T.J. Mercier wrote:
> > The arguments for __dma_buf_debugfs_list_del do not match for both the
> > CONFIG_DEBUG_FS case and the !CONFIG_DEBUG_FS case. The !CONFIG_DEBUG_FS
> > case should take a struct dma_buf *, but it's currently struct file *.
> > This can lead to the build error:
> >
> > error: passing argument 1 of ‘__dma_buf_debugfs_list_del’ from
> > incompatible pointer type [-Werror=incompatible-pointer-types]
> >
> > dma-buf.c:63:53: note: expected ‘struct file *’ but argument is of
> > type ‘struct dma_buf *’
> > 63 | static void __dma_buf_debugfs_list_del(struct file *file)
> >
> > Fixes: bfc7bc539392 ("dma-buf: Do not build debugfs related code when !CONFIG_DEBUG_FS")
> > Signed-off-by: T.J. Mercier <tjmercier(a)google.com>
> > ---
> > drivers/dma-buf/dma-buf.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> > index 8892bc701a66..afb8c1c50107 100644
> > --- a/drivers/dma-buf/dma-buf.c
> > +++ b/drivers/dma-buf/dma-buf.c
> > @@ -60,7 +60,7 @@ static void __dma_buf_debugfs_list_add(struct dma_buf *dmabuf)
> > {
> > }
> >
> > -static void __dma_buf_debugfs_list_del(struct file *file)
> > +static void __dma_buf_debugfs_list_del(struct dma_buf *dmabuf)
> > {
> > }
> > #endif
>
> Huh I wonder how this sneaked by until now.. thanks for fixing!
>
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin(a)igalia.com>
>
> Regards,
>
> Tvrtko
Thanks Tvrtko. Upstream there is currently only the one use where it's
called with a void pointer which doesn't generate the error, but
KernelCI caught the problem on an Android branch where it's also
called with a dma_buf pointer:
https://dashboard.kernelci.org/tree/5a4c93e2f794001a5efa13c0dec931235240d38…
The arguments for __dma_buf_debugfs_list_del do not match for both the
CONFIG_DEBUG_FS case and the !CONFIG_DEBUG_FS case. The !CONFIG_DEBUG_FS
case should take a struct dma_buf *, but it's currently struct file *.
This can lead to the build error:
error: passing argument 1 of ‘__dma_buf_debugfs_list_del’ from
incompatible pointer type [-Werror=incompatible-pointer-types]
dma-buf.c:63:53: note: expected ‘struct file *’ but argument is of
type ‘struct dma_buf *’
63 | static void __dma_buf_debugfs_list_del(struct file *file)
Fixes: bfc7bc539392 ("dma-buf: Do not build debugfs related code when !CONFIG_DEBUG_FS")
Signed-off-by: T.J. Mercier <tjmercier(a)google.com>
---
drivers/dma-buf/dma-buf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 8892bc701a66..afb8c1c50107 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -60,7 +60,7 @@ static void __dma_buf_debugfs_list_add(struct dma_buf *dmabuf)
{
}
-static void __dma_buf_debugfs_list_del(struct file *file)
+static void __dma_buf_debugfs_list_del(struct dma_buf *dmabuf)
{
}
#endif
--
2.47.0.338.g60cca15819-goog
Am 14.11.24 um 12:14 schrieb Tvrtko Ursulin:
> From: Tvrtko Ursulin <tvrtko.ursulin(a)igalia.com>
>
> One alternative to the fix Christian proposed in
> https://lore.kernel.org/dri-devel/20241024124159.4519-3-christian.koenig@am…
> is to replace the rather complex open coded sorting loops with the kernel
> standard sort followed by a context squashing pass.
>
> Proposed advantage of this would be readability but one concern Christian
> raised was that there could be many fences, that they are typically mostly
> sorted, and so the kernel's heap sort would be much worse by the proposed
> algorithm.
>
> I had a look running some games and vkcube to see what are the typical
> number of input fences. Tested scenarios:
>
> 1) Hogwarts Legacy under Gamescope
>
> 450 calls per second to __dma_fence_unwrap_merge.
>
> Percentages per number of fences buckets, before and after checking for
> signalled status, sorting and flattening:
>
> N Before After
> 0 0.91%
> 1 69.40%
> 2-3 28.72% 9.4% (90.6% resolved to one fence)
> 4-5 0.93%
> 6-9 0.03%
> 10+
>
> 2) Cyberpunk 2077 under Gamescope
>
> 1050 calls per second, amounting to 0.01% CPU time according to perf top.
>
> N Before After
> 0 1.13%
> 1 52.30%
> 2-3 40.34% 55.57%
> 4-5 1.46% 0.50%
> 6-9 2.44%
> 10+ 2.34%
>
> 3) vkcube under Plasma
>
> 90 calls per second.
>
> N Before After
> 0
> 1
> 2-3 100% 0% (Ie. all resolved to a single fence)
> 4-5
> 6-9
> 10+
>
> In the case of vkcube all invocations in the 2-3 bucket were actually
> just two input fences.
>
> From these numbers it looks like the heap sort should not be a
> disadvantage, given how the dominant case is <= 2 input fences which heap
> sort solves with just one compare and swap. (And for the case of one input
> fence we have a fast path in the previous patch.)
>
> A complementary possibility is to implement a different sorting algorithm
> under the same API as the kernel's sort() and so keep the simplicity,
> potentially moving the new sort under lib/ if it would be found more
> widely useful.
>
> v2:
> * Hold on to fence references and reduce commentary. (Christian)
> * Record and use latest signaled timestamp in the 2nd loop too.
> * Consolidate zero or one fences fast paths.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin(a)igalia.com>
> Fixes: 245a4a7b531c ("dma-buf: generalize dma_fence unwrap & merging v3")
> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3617
> Cc: Christian König <christian.koenig(a)amd.com>
> Cc: Daniel Vetter <daniel.vetter(a)ffwll.ch>
> Cc: Sumit Semwal <sumit.semwal(a)linaro.org>
> Cc: Gustavo Padovan <gustavo(a)padovan.org>
> Cc: Friedrich Vock <friedrich.vock(a)gmx.de>
> Cc: linux-media(a)vger.kernel.org
> Cc: dri-devel(a)lists.freedesktop.org
> Cc: linaro-mm-sig(a)lists.linaro.org
> Cc: <stable(a)vger.kernel.org> # v6.0+
> ---
> drivers/dma-buf/dma-fence-unwrap.c | 129 ++++++++++++++---------------
> 1 file changed, 64 insertions(+), 65 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-fence-unwrap.c b/drivers/dma-buf/dma-fence-unwrap.c
> index 628af51c81af..26cad03340ce 100644
> --- a/drivers/dma-buf/dma-fence-unwrap.c
> +++ b/drivers/dma-buf/dma-fence-unwrap.c
> @@ -12,6 +12,7 @@
> #include <linux/dma-fence-chain.h>
> #include <linux/dma-fence-unwrap.h>
> #include <linux/slab.h>
> +#include <linux/sort.h>
>
> /* Internal helper to start new array iteration, don't use directly */
> static struct dma_fence *
> @@ -59,6 +60,25 @@ struct dma_fence *dma_fence_unwrap_next(struct dma_fence_unwrap *cursor)
> }
> EXPORT_SYMBOL_GPL(dma_fence_unwrap_next);
>
> +
> +static int fence_cmp(const void *_a, const void *_b)
> +{
> + struct dma_fence *a = *(struct dma_fence **)_a;
> + struct dma_fence *b = *(struct dma_fence **)_b;
> +
> + if (a->context < b->context)
> + return -1;
> + else if (a->context > b->context)
> + return 1;
> +
> + if (dma_fence_is_later(b, a))
> + return -1;
> + else if (dma_fence_is_later(a, b))
> + return 1;
> +
> + return 0;
> +}
> +
> /* Implementation for the dma_fence_merge() marco, don't use directly */
> struct dma_fence *__dma_fence_unwrap_merge(unsigned int num_fences,
> struct dma_fence **fences,
> @@ -67,8 +87,7 @@ struct dma_fence *__dma_fence_unwrap_merge(unsigned int num_fences,
> struct dma_fence_array *result;
> struct dma_fence *tmp, **array;
> ktime_t timestamp;
> - unsigned int i;
> - size_t count;
> + int i, j, count;
>
> count = 0;
> timestamp = ns_to_ktime(0);
> @@ -96,78 +115,58 @@ struct dma_fence *__dma_fence_unwrap_merge(unsigned int num_fences,
> if (!array)
> return NULL;
>
> - /*
> - * This trashes the input fence array and uses it as position for the
> - * following merge loop. This works because the dma_fence_merge()
> - * wrapper macro is creating this temporary array on the stack together
> - * with the iterators.
> - */
> - for (i = 0; i < num_fences; ++i)
> - fences[i] = dma_fence_unwrap_first(fences[i], &iter[i]);
> -
> count = 0;
> - do {
> - unsigned int sel;
> -
> -restart:
> - tmp = NULL;
> - for (i = 0; i < num_fences; ++i) {
> - struct dma_fence *next;
> -
> - while (fences[i] && dma_fence_is_signaled(fences[i]))
> - fences[i] = dma_fence_unwrap_next(&iter[i]);
> -
> - next = fences[i];
> - if (!next)
> - continue;
> -
> - /*
> - * We can't guarantee that inpute fences are ordered by
> - * context, but it is still quite likely when this
> - * function is used multiple times. So attempt to order
> - * the fences by context as we pass over them and merge
> - * fences with the same context.
> - */
> - if (!tmp || tmp->context > next->context) {
> - tmp = next;
> - sel = i;
> -
> - } else if (tmp->context < next->context) {
> - continue;
> -
> - } else if (dma_fence_is_later(tmp, next)) {
> - fences[i] = dma_fence_unwrap_next(&iter[i]);
> - goto restart;
> + for (i = 0; i < num_fences; ++i) {
> + dma_fence_unwrap_for_each(tmp, &iter[i], fences[i]) {
> + if (!dma_fence_is_signaled(tmp)) {
> + array[count++] = dma_fence_get(tmp);
> } else {
> - fences[sel] = dma_fence_unwrap_next(&iter[sel]);
> - goto restart;
> + ktime_t t = dma_fence_timestamp(tmp);
> +
> + if (ktime_after(t, timestamp))
> + timestamp = t;
> }
> }
> + }
>
> - if (tmp) {
> - array[count++] = dma_fence_get(tmp);
> - fences[sel] = dma_fence_unwrap_next(&iter[sel]);
> + if (count == 0 || count == 1)
> + goto return_fastpath;
> +
> + sort(array, count, sizeof(*array), fence_cmp, NULL);
> +
> + /*
> + * Only keep the most recent fence for each context.
> + */
> + j = 0;
> + tmp = array[0];
> + for (i = 1; i < count; i++) {
> + if (array[i]->context != tmp->context)
> + array[j++] = tmp;
> + else
> + dma_fence_put(tmp);
If I'm not completely mistaken that can result in dropping the first
element but not assigning it again.
E.g. array[0] is potentially invalid after the loop.
> + tmp = array[i];
> + }
> + if (j == 0 || tmp->context != array[j - 1]->context) {
> + array[j++] = tmp;
> + }
Maybe adjust the sort criteria so that the highest seqno comes first.
This reduces the whole loop to something like this:
j = 0;
for (i = 1; i < count; i++) {
if (array[i]->context == array[j]->context)
dma_fence_put(array[i]);
else
array[++j] = array[i];
}
count = ++j;
Regards,
Christian.
> + count = j;
> +
> + if (count > 1) {
> + result = dma_fence_array_create(count, array,
> + dma_fence_context_alloc(1),
> + 1, false);
> + if (!result) {
> + tmp = NULL;
> + goto return_tmp;
> }
> - } while (tmp);
> -
> - if (count == 0) {
> - tmp = dma_fence_allocate_private_stub(ktime_get());
> - goto return_tmp;
> + return &result->base;
> }
>
> - if (count == 1) {
> +return_fastpath:
> + if (count == 0)
> + tmp = dma_fence_allocate_private_stub(timestamp);
> + else
> tmp = array[0];
> - goto return_tmp;
> - }
> -
> - result = dma_fence_array_create(count, array,
> - dma_fence_context_alloc(1),
> - 1, false);
> - if (!result) {
> - tmp = NULL;
> - goto return_tmp;
> - }
> - return &result->base;
>
> return_tmp:
> kfree(array);
On Mon, Nov 11, 2024 at 07:32:42PM +0530, Jyothi Kumar Seerapu wrote:
> GSI hardware generates an interrupt for each transfer completion.
> For multiple messages within a single transfer, this results
> in receiving N interrupts for N messages, which can introduce
> significant software interrupt latency.
Here's an excellent opportunity for splitting your problem description
and solution description in two easy to read paragraphs by adding some
newlines.
> To mitigate this latency,
> utilize Block Event Interrupt (BEI) only when an interrupt is necessary.
> When using BEI, consider splitting a single multi-message transfer into
> chunks of 8. This approach can enhance overall transfer time and
The reason for the number 8 must be documented.
"This approach..." wouldn't hurt from having it's own paragraph once
again.
> efficiency.
>
> Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu(a)quicinc.com>
> ---
>
> v1 -> v2:
> - Changed dma_addr type from array of pointers to array.
> - To support BEI functionality with the TRE size of 64 defined in GPI driver,
> updated QCOM_GPI_MAX_NUM_MSGS to 16 and NUM_MSGS_PER_IRQ to 8.
>
> drivers/dma/qcom/gpi.c | 49 ++++++++++++++++++++++++++++++++
> include/linux/dma/qcom-gpi-dma.h | 37 ++++++++++++++++++++++++
> 2 files changed, 86 insertions(+)
>
> diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c
> index 52a7c8f2498f..a98de3178764 100644
> --- a/drivers/dma/qcom/gpi.c
> +++ b/drivers/dma/qcom/gpi.c
> @@ -1693,6 +1693,9 @@ static int gpi_create_i2c_tre(struct gchan *chan, struct gpi_desc *desc,
>
> tre->dword[3] = u32_encode_bits(TRE_TYPE_DMA, TRE_FLAGS_TYPE);
> tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_IEOT);
> +
> + if (i2c->flags & QCOM_GPI_BLOCK_EVENT_IRQ)
> + tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_BEI);
> }
>
> for (i = 0; i < tre_idx; i++)
> @@ -2098,6 +2101,52 @@ static int gpi_find_avail_gpii(struct gpi_dev *gpi_dev, u32 seid)
> return -EIO;
> }
>
> +/**
> + * gpi_multi_desc_process() - Process received transfers from GSI HW
> + * @dev: pointer to the corresponding dev node
> + * @multi_xfer: pointer to the gpi_multi_xfer
> + * @num_xfers: total number of transfers
> + * @transfer_timeout_msecs: transfer timeout value
> + * @transfer_comp: completion object of the transfer
> + *
> + * This function is used to process the received transfers based on the
> + * completion events
As far as I can tell it doesn't "process" anything. All it does is
reinit the completion (n + 7) / 8 times, and for the first n / 8
iterations it will wait for an externally defined completion.
Why is this function even defined here, it solely operates on parameters
coming from the I2C driver?
> + *
> + * Return: On success returns 0, otherwise return error code
> + */
> +int gpi_multi_desc_process(struct device *dev, struct gpi_multi_xfer *multi_xfer,
> + u32 num_xfers, u32 transfer_timeout_msecs,
> + struct completion *transfer_comp)
> +{
> + int i;
> + u32 max_irq_cnt, time_left;
> +
> + max_irq_cnt = num_xfers / NUM_MSGS_PER_IRQ;
> + if (num_xfers % NUM_MSGS_PER_IRQ)
> + max_irq_cnt++;
> +
> + /*
> + * Wait for the interrupts of the processed transfers in multiple
> + * of 64 and for the last transfer. If the hardware is fast and
I'm confused, where does this 64 come from?
> + * already processed all the transfers then no need to wait.
> + */
> + for (i = 0; i < max_irq_cnt; i++) {
> + reinit_completion(transfer_comp);
I'm trying to convince myself that this isn't racey, but the split
ownership of updating and checking multi_xfer->irq_cnt between the GPI
and I2C drivers is just too hard for me to follow.
> + if (max_irq_cnt != multi_xfer->irq_cnt) {
> + time_left = wait_for_completion_timeout(transfer_comp,
> + transfer_timeout_msecs);
> + if (!time_left) {
> + dev_err(dev, "%s: Transfer timeout\n", __func__);
> + return -ETIMEDOUT;
> + }
> + }
> + if (num_xfers > multi_xfer->msg_idx_cnt)
> + return 0;
> + }
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(gpi_multi_desc_process);
The dmaengine framework is expected to provide an abstraction between
clients and DMA engines, so this doesn't look right.
> +
> /* gpi_of_dma_xlate: open client requested channel */
> static struct dma_chan *gpi_of_dma_xlate(struct of_phandle_args *args,
> struct of_dma *of_dma)
> diff --git a/include/linux/dma/qcom-gpi-dma.h b/include/linux/dma/qcom-gpi-dma.h
> index 6680dd1a43c6..1341ff0db808 100644
> --- a/include/linux/dma/qcom-gpi-dma.h
> +++ b/include/linux/dma/qcom-gpi-dma.h
> @@ -15,6 +15,12 @@ enum spi_transfer_cmd {
> SPI_DUPLEX,
> };
>
> +#define QCOM_GPI_BLOCK_EVENT_IRQ BIT(0)
> +
> +#define QCOM_GPI_MAX_NUM_MSGS 16
> +#define NUM_MSGS_PER_IRQ 8
> +#define MIN_NUM_OF_MSGS_MULTI_DESC 4
Prefixing these QCOM_GPI_ seems like an excellent idea. Still puzzled
about the numbers 8 and 4 though, are they universal for all variants of
GPI or are they just arbitrary numbers picked by experimentation?
> +
> /**
> * struct gpi_spi_config - spi config for peripheral
> *
> @@ -51,6 +57,29 @@ enum i2c_op {
> I2C_READ,
> };
>
> +/**
> + * struct gpi_multi_xfer - Used for multi transfer support
> + *
> + * @msg_idx_cnt: message index for the transfer
> + * @buf_idx: dma buffer index
> + * @unmap_msg_cnt: unampped transfer index
s/unampped/unmapped
> + * @freed_msg_cnt: freed transfer index
> + * @irq_cnt: received interrupt count
> + * @irq_msg_cnt: transfer message count for the received irqs
> + * @dma_buf: virtual address of the buffer
> + * @dma_addr: dma address of the buffer
"the buffer"? There's up to 16 of them...
As mentioned above, I'm skeptical about this custom API - but if we
were to go this route, the exact responsibilities and semantics should
be documented.
Regards,
Bjorn
> + */
> +struct gpi_multi_xfer {
> + u32 msg_idx_cnt;
> + u32 buf_idx;
> + u32 unmap_msg_cnt;
> + u32 freed_msg_cnt;
> + u32 irq_cnt;
> + u32 irq_msg_cnt;
> + void *dma_buf[QCOM_GPI_MAX_NUM_MSGS];
> + dma_addr_t dma_addr[QCOM_GPI_MAX_NUM_MSGS];
> +};
> +
> /**
> * struct gpi_i2c_config - i2c config for peripheral
> *
> @@ -65,6 +94,8 @@ enum i2c_op {
> * @rx_len: receive length for buffer
> * @op: i2c cmd
> * @muli-msg: is part of multi i2c r-w msgs
> + * @flags: true for block event interrupt support
> + * @multi_xfer: indicates transfer has multi messages
> */
> struct gpi_i2c_config {
> u8 set_config;
> @@ -78,6 +109,12 @@ struct gpi_i2c_config {
> u32 rx_len;
> enum i2c_op op;
> bool multi_msg;
> + u8 flags;
> + struct gpi_multi_xfer multi_xfer;
> };
>
> +int gpi_multi_desc_process(struct device *dev, struct gpi_multi_xfer *multi_xfer,
> + u32 num_xfers, u32 tranfer_timeout_msecs,
> + struct completion *transfer_comp);
> +
> #endif /* QCOM_GPI_DMA_H */
> --
> 2.17.1
>
>