From: Daniel Vetter <daniel.vetter@ffwll.ch> To: DRI Development <dri-devel@lists.freedesktop.org> Cc: linux-arm-kernel@lists.infradead.org, Andy Shevchenko <andriy.shevchenko@intel.com>, Daniel Vetter <daniel.vetter@ffwll.ch>, Robert Jarzmik <robert.jarzmik@free.fr>, Haojian Zhuang <haojian.zhuang@gmail.com>, linux-spi@vger.kernel.org, Mark Brown <broonie@kernel.org>, Sam Ravnborg <sam@ravnborg.org>, Daniel Mack <daniel@zonque.org> Subject: [PATCH] spi: pxa2xx: Set controller->max_transfer_size in dma mode Date: Wed, 16 Oct 2019 21:57:21 +0200 [thread overview] Message-ID: <20191016195721.3714-1-daniel.vetter@ffwll.ch> (raw) In DMA mode we have a maximum transfer size, past that the driver falls back to PIO (see the check at the top of pxa2xx_spi_transfer_one). Falling back to PIO for big transfers defeats the point of a dma engine, hence set the max transfer size to inform spi clients that they need to do something smarter. This was uncovered by the drm_mipi_dbi spi panel code, which does large spi transfers, but stopped splitting them after: commit e143364b4c1774f68e923a5a0bb0fca28ac25888 Author: Noralf Trønnes <noralf@tronnes.org> Date: Fri Jul 19 17:59:10 2019 +0200 drm/tinydrm: Remove tinydrm_spi_max_transfer_size() After this commit the code relied on the spi core to split transfers into max dma-able blocks, which also papered over the PIO fallback issue. Fix this by setting the overall max transfer size to the DMA limit, but only when the controller runs in DMA mode. Fixes: e143364b4c17 ("drm/tinydrm: Remove tinydrm_spi_max_transfer_size()") Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Noralf Trønnes <noralf@tronnes.org> Cc: Andy Shevchenko <andriy.shevchenko@intel.com> Reported-and-tested-by: Andy Shevchenko <andriy.shevchenko@intel.com> Cc: Daniel Mack <daniel@zonque.org> Cc: Haojian Zhuang <haojian.zhuang@gmail.com> Cc: Robert Jarzmik <robert.jarzmik@free.fr> Cc: Mark Brown <broonie@kernel.org> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-spi@vger.kernel.org Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> --- drivers/spi/spi-pxa2xx.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c index bb6a14d1ab0f..f77201915033 100644 --- a/drivers/spi/spi-pxa2xx.c +++ b/drivers/spi/spi-pxa2xx.c @@ -1707,6 +1707,7 @@ static int pxa2xx_spi_probe(struct platform_device *pdev) } else { controller->can_dma = pxa2xx_spi_can_dma; controller->max_dma_len = MAX_DMA_LEN; + controller->max_transfer_size = MAX_DMA_LEN; } } -- 2.23.0 _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
WARNING: multiple messages have this Message-ID (diff)
From: Daniel Vetter <daniel.vetter@ffwll.ch> To: DRI Development <dri-devel@lists.freedesktop.org> Cc: linux-arm-kernel@lists.infradead.org, "Andy Shevchenko" <andriy.shevchenko@intel.com>, "Daniel Vetter" <daniel.vetter@ffwll.ch>, "Robert Jarzmik" <robert.jarzmik@free.fr>, "Haojian Zhuang" <haojian.zhuang@gmail.com>, linux-spi@vger.kernel.org, "Noralf Trønnes" <noralf@tronnes.org>, "Mark Brown" <broonie@kernel.org>, "Sam Ravnborg" <sam@ravnborg.org>, "Daniel Mack" <daniel@zonque.org> Subject: [PATCH] spi: pxa2xx: Set controller->max_transfer_size in dma mode Date: Wed, 16 Oct 2019 21:57:21 +0200 [thread overview] Message-ID: <20191016195721.3714-1-daniel.vetter@ffwll.ch> (raw) In DMA mode we have a maximum transfer size, past that the driver falls back to PIO (see the check at the top of pxa2xx_spi_transfer_one). Falling back to PIO for big transfers defeats the point of a dma engine, hence set the max transfer size to inform spi clients that they need to do something smarter. This was uncovered by the drm_mipi_dbi spi panel code, which does large spi transfers, but stopped splitting them after: commit e143364b4c1774f68e923a5a0bb0fca28ac25888 Author: Noralf Trønnes <noralf@tronnes.org> Date: Fri Jul 19 17:59:10 2019 +0200 drm/tinydrm: Remove tinydrm_spi_max_transfer_size() After this commit the code relied on the spi core to split transfers into max dma-able blocks, which also papered over the PIO fallback issue. Fix this by setting the overall max transfer size to the DMA limit, but only when the controller runs in DMA mode. Fixes: e143364b4c17 ("drm/tinydrm: Remove tinydrm_spi_max_transfer_size()") Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Noralf Trønnes <noralf@tronnes.org> Cc: Andy Shevchenko <andriy.shevchenko@intel.com> Reported-and-tested-by: Andy Shevchenko <andriy.shevchenko@intel.com> Cc: Daniel Mack <daniel@zonque.org> Cc: Haojian Zhuang <haojian.zhuang@gmail.com> Cc: Robert Jarzmik <robert.jarzmik@free.fr> Cc: Mark Brown <broonie@kernel.org> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-spi@vger.kernel.org Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> --- drivers/spi/spi-pxa2xx.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c index bb6a14d1ab0f..f77201915033 100644 --- a/drivers/spi/spi-pxa2xx.c +++ b/drivers/spi/spi-pxa2xx.c @@ -1707,6 +1707,7 @@ static int pxa2xx_spi_probe(struct platform_device *pdev) } else { controller->can_dma = pxa2xx_spi_can_dma; controller->max_dma_len = MAX_DMA_LEN; + controller->max_transfer_size = MAX_DMA_LEN; } } -- 2.23.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2019-10-16 19:57 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-16 19:57 Daniel Vetter [this message] 2019-10-16 19:57 ` [PATCH] spi: pxa2xx: Set controller->max_transfer_size in dma mode Daniel Vetter 2019-10-16 21:30 ` Noralf Trønnes 2019-10-16 21:30 ` Noralf Trønnes 2019-10-16 21:49 ` Mark Brown 2019-10-16 21:49 ` Mark Brown 2019-10-17 6:44 ` Daniel Vetter 2019-10-17 7:06 ` Andy Shevchenko 2019-10-17 7:06 ` Andy Shevchenko 2019-10-21 11:08 ` Andy Shevchenko 2019-10-21 11:08 ` Andy Shevchenko 2019-10-21 11:35 ` Mark Brown 2019-10-21 11:35 ` Mark Brown
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