[PATCH 1/2] mmc: meson-gx: make replace WARN_ONCE with dev_warn_once about scatterlist offset alignment

[PATCH 1/2] mmc: meson-gx: make replace WARN_ONCE with dev_warn_once about scatterlist offset alignment

[Neil Armstrong]

Some drivers like ath10k can sometimg give an sg buffer with an offset whose alignment
is not compatible with the Amlogic DMA descriptor engine requirements.

Simply replace with dev_warn_once() to inform user this should be fixed to avoid
degraded performance.

This should be ultimately fixed in ath10k, but since it's only a performance issue
the warning should be removed.

Fixes: 79ed05e329c3 ("mmc: meson-gx: add support for descriptor chain mode")
Reported-by: Christian Hewitt <christianshewitt@gmail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
---
 drivers/mmc/host/meson-gx-mmc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index b8b771b643cc..1c61f0f24c09 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -258,7 +258,9 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
 	for_each_sg(data->sg, sg, data->sg_len, i) {
 		/* check for 8 byte alignment */
 		if (sg->offset % 8) {
-			WARN_ONCE(1, "unaligned scatterlist buffer\n");
+			dev_warn_once(mmc_dev(mmc),
+				      "unaligned sg offset %u, disabling descriptor DMA for transfer\n",
+				      sg->offset);
 			return;
 		}
 	}
-- 
2.25.1

[PATCH 2/2] mmc: meson-gx: also check SD_IO_RW_EXTENDED for scatterlist size alignment

[Neil Armstrong]

The brcmfmac driver can generate a scatterlist from a skb with each packets
not aligned to the block size. This is not supported by the Amlogic Descriptor
dma engine where each descriptor must match a multiple of the block size.

The sg list is valid, since the sum of the sg buffers is a multiple of the
block size, but we must discard those when in SD_IO_RW_EXTENDED mode since
SDIO block mode can be used under the hood even with data->blocks == 1.

Those transfers are very rare, thus can be replaced by a bounce buffer
without real performance loss.

Fixes: 7412dee9f1fd ("mmc: meson-gx: replace WARN_ONCE with dev_warn_once about scatterlist size alignment in block mode")
Reported-by: Christian Hewitt <christianshewitt@gmail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
---
 drivers/mmc/host/meson-gx-mmc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index 1c61f0f24c09..016a6106151a 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -236,7 +236,8 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
 	if (host->dram_access_quirk)
 		return;
 
-	if (data->blocks > 1) {
+	/* SD_IO_RW_EXTENDED (CMD53) can also use block mode under the hood */
+	if (data->blocks > 1 || mrq->cmd->opcode == SD_IO_RW_EXTENDED) {
 		/*
 		 * In block mode DMA descriptor format, "length" field indicates
 		 * number of blocks and there is no way to pass DMA size that
-- 
2.25.1

Re: [PATCH 2/2] mmc: meson-gx: also check SD_IO_RW_EXTENDED for scatterlist size alignment

[Ulf Hansson]

On Mon, 26 Apr 2021 at 19:56, Neil Armstrong <narmstrong@baylibre.com> wrote:
>
> The brcmfmac driver can generate a scatterlist from a skb with each packets
> not aligned to the block size. This is not supported by the Amlogic Descriptor
> dma engine where each descriptor must match a multiple of the block size.
>
> The sg list is valid, since the sum of the sg buffers is a multiple of the
> block size, but we must discard those when in SD_IO_RW_EXTENDED mode since
> SDIO block mode can be used under the hood even with data->blocks == 1.
>
> Those transfers are very rare, thus can be replaced by a bounce buffer
> without real performance loss.
>
> Fixes: 7412dee9f1fd ("mmc: meson-gx: replace WARN_ONCE with dev_warn_once about scatterlist size alignment in block mode")
> Reported-by: Christian Hewitt <christianshewitt@gmail.com>
> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

Applied for fixes and by adding a stable tag, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/meson-gx-mmc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> index 1c61f0f24c09..016a6106151a 100644
> --- a/drivers/mmc/host/meson-gx-mmc.c
> +++ b/drivers/mmc/host/meson-gx-mmc.c
> @@ -236,7 +236,8 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
>         if (host->dram_access_quirk)
>                 return;
>
> -       if (data->blocks > 1) {
> +       /* SD_IO_RW_EXTENDED (CMD53) can also use block mode under the hood */
> +       if (data->blocks > 1 || mrq->cmd->opcode == SD_IO_RW_EXTENDED) {
>                 /*
>                  * In block mode DMA descriptor format, "length" field indicates
>                  * number of blocks and there is no way to pass DMA size that
> --
> 2.25.1
>

Re: [PATCH 1/2] mmc: meson-gx: make replace WARN_ONCE with dev_warn_once about scatterlist offset alignment

[Martin Blumenstingl]

Hi Neil,

On Mon, Apr 26, 2021 at 7:58 PM Neil Armstrong <narmstrong@baylibre.com> wrote:
>
> Some drivers like ath10k can sometimg give an sg buffer with an offset whose alignment
sometimg -> sometimes

> is not compatible with the Amlogic DMA descriptor engine requirements.
>
> Simply replace with dev_warn_once() to inform user this should be fixed to avoid
> degraded performance.
>
> This should be ultimately fixed in ath10k, but since it's only a performance issue
> the warning should be removed.
>
> Fixes: 79ed05e329c3 ("mmc: meson-gx: add support for descriptor chain mode")
> Reported-by: Christian Hewitt <christianshewitt@gmail.com>
> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

Re: [PATCH 1/2] mmc: meson-gx: make replace WARN_ONCE with dev_warn_once about scatterlist offset alignment

[Ulf Hansson]

On Mon, 26 Apr 2021 at 19:56, Neil Armstrong <narmstrong@baylibre.com> wrote:
>
> Some drivers like ath10k can sometimg give an sg buffer with an offset whose alignment
> is not compatible with the Amlogic DMA descriptor engine requirements.
>
> Simply replace with dev_warn_once() to inform user this should be fixed to avoid
> degraded performance.
>
> This should be ultimately fixed in ath10k, but since it's only a performance issue
> the warning should be removed.
>
> Fixes: 79ed05e329c3 ("mmc: meson-gx: add support for descriptor chain mode")
> Reported-by: Christian Hewitt <christianshewitt@gmail.com>
> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

Applied for fixes and by adding a stable tag, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/meson-gx-mmc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> index b8b771b643cc..1c61f0f24c09 100644
> --- a/drivers/mmc/host/meson-gx-mmc.c
> +++ b/drivers/mmc/host/meson-gx-mmc.c
> @@ -258,7 +258,9 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
>         for_each_sg(data->sg, sg, data->sg_len, i) {
>                 /* check for 8 byte alignment */
>                 if (sg->offset % 8) {
> -                       WARN_ONCE(1, "unaligned scatterlist buffer\n");
> +                       dev_warn_once(mmc_dev(mmc),
> +                                     "unaligned sg offset %u, disabling descriptor DMA for transfer\n",
> +                                     sg->offset);
>                         return;
>                 }
>         }
> --
> 2.25.1
>