| Message ID | 20220304135134.47827-2-yann.gautier@foss.st.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mmc: mmci: stm32: updates for SDIO | expand |
Hi Yann, On Fri, 4 Mar 2022 at 14:52, Yann Gautier <yann.gautier@foss.st.com> wrote: > > On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported > starting from revision v2 of the peripheral. But it has limitations, > as all the buffers should be aligned on block size (except the last one). > But this cannot be guaranteed with SDIO. We should then have a property > to disable the support of LLI. Indeed, the buffer handling with SDIO is somewhat special, which also has been discussed several times on LKML before. In principle, we need the SDIO func drivers to respect buffer limitations that should be specified by the mmc host drivers. Quite similar to what we already have for block devices, like ->max_seg_size, ->max_seg, etc, that is set per mmc host. I realize that implementing something like the above requires bigger changes, which is why mmc host drivers instead validates the sglists and the elements. In some cases that means returning an error code and in others it could mean falling back to a non-DMA based I/O mode. For the stm32_sdmmc variant, it looks like the sglist validation is being managed in sdmmc_idma_validate_data() already. Can it be extended to cover this case too, rather than using a DT property? Kind regards Uffe > > Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> > --- > Documentation/devicetree/bindings/mmc/arm,pl18x.yaml | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml b/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml > index 1e69a5a42439..309a2c0426e5 100644 > --- a/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml > +++ b/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml > @@ -145,6 +145,11 @@ properties: > driver to sample the receive data (for example with a voltage switch > transceiver). > > + st,disable-dma-lli: > + $ref: /schemas/types.yaml#/definitions/flag > + description: ST Micro-specific property, disable DMA linked lists. > + It is used for SDIO. > + > st,cmd-gpios: > maxItems: 1 > description: > -- > 2.25.1 >
On 3/8/22 11:57, Ulf Hansson wrote: > Hi Yann, > > On Fri, 4 Mar 2022 at 14:52, Yann Gautier <yann.gautier@foss.st.com> wrote: >> >> On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported >> starting from revision v2 of the peripheral. But it has limitations, >> as all the buffers should be aligned on block size (except the last one). >> But this cannot be guaranteed with SDIO. We should then have a property >> to disable the support of LLI. > > Indeed, the buffer handling with SDIO is somewhat special, which also > has been discussed several times on LKML before. In principle, we need > the SDIO func drivers to respect buffer limitations that should be > specified by the mmc host drivers. Quite similar to what we already > have for block devices, like ->max_seg_size, ->max_seg, etc, that is > set per mmc host. > > I realize that implementing something like the above requires bigger > changes, which is why mmc host drivers instead validates the sglists > and the elements. In some cases that means returning an error code and > in others it could mean falling back to a non-DMA based I/O mode. > > For the stm32_sdmmc variant, it looks like the sglist validation is > being managed in sdmmc_idma_validate_data() already. Can it be > extended to cover this case too, rather than using a DT property? > > Kind regards > Uffe Hi Ulf, OK, I'll check what can be done for this. Patches 1 and 2 can be dropped, they will be reworked. But patch 3 of this series could be taken, as not linked to LLI management. Should I push it again alone, or could you review it directly? Best regards, Yann > >> >> Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> >> --- >> Documentation/devicetree/bindings/mmc/arm,pl18x.yaml | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml b/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml >> index 1e69a5a42439..309a2c0426e5 100644 >> --- a/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml >> +++ b/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml >> @@ -145,6 +145,11 @@ properties: >> driver to sample the receive data (for example with a voltage switch >> transceiver). >> >> + st,disable-dma-lli: >> + $ref: /schemas/types.yaml#/definitions/flag >> + description: ST Micro-specific property, disable DMA linked lists. >> + It is used for SDIO. >> + >> st,cmd-gpios: >> maxItems: 1 >> description: >> -- >> 2.25.1 >>
On Thu, 10 Mar 2022 at 17:00, Yann Gautier <yann.gautier@foss.st.com> wrote: > > On 3/8/22 11:57, Ulf Hansson wrote: > > Hi Yann, > > > > On Fri, 4 Mar 2022 at 14:52, Yann Gautier <yann.gautier@foss.st.com> wrote: > >> > >> On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported > >> starting from revision v2 of the peripheral. But it has limitations, > >> as all the buffers should be aligned on block size (except the last one). > >> But this cannot be guaranteed with SDIO. We should then have a property > >> to disable the support of LLI. > > > > Indeed, the buffer handling with SDIO is somewhat special, which also > > has been discussed several times on LKML before. In principle, we need > > the SDIO func drivers to respect buffer limitations that should be > > specified by the mmc host drivers. Quite similar to what we already > > have for block devices, like ->max_seg_size, ->max_seg, etc, that is > > set per mmc host. > > > > I realize that implementing something like the above requires bigger > > changes, which is why mmc host drivers instead validates the sglists > > and the elements. In some cases that means returning an error code and > > in others it could mean falling back to a non-DMA based I/O mode. > > > > For the stm32_sdmmc variant, it looks like the sglist validation is > > being managed in sdmmc_idma_validate_data() already. Can it be > > extended to cover this case too, rather than using a DT property? > > > > Kind regards > > Uffe > > Hi Ulf, > > OK, I'll check what can be done for this. Patches 1 and 2 can be > dropped, they will be reworked. Okay. > But patch 3 of this series could be taken, as not linked to LLI > management. Should I push it again alone, or could you review it directly? I have some comments/questions on it, but perhaps it makes it easier for people to follow the discussion if it is done separately. So please push it alone, then I will review it. [...] Kind regards Uffe
"On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier <yann.gautier@foss.st.com> wrote: > On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported > starting from revision v2 of the peripheral. But it has limitations, > as all the buffers should be aligned on block size (except the last one). > But this cannot be guaranteed with SDIO. We should then have a property > to disable the support of LLI. > > Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> Actually I think this is present also on the ux500 variants. See: commit 2253ed4b36dc876d1598c4dab5587e537ec68c34 "mmc: mmci: Support any block sizes for ux500v2 and qcom variant" Spot the variant data "dma_power_of_2". So whatever property you add to the variant data (not in the device tree please) should be added to the ux500 variants as well, it will *VERY* likely have a problem with LLI elements not being a power of 2 as it is the ancestor of later STMicro variants. It might actually be the reason for some annoying WiFi error messages I have seen :/ Yours, Linus Walleij
On 3/14/22 23:43, Linus Walleij wrote: > "On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier <yann.gautier@foss.st.com> wrote: > >> On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported >> starting from revision v2 of the peripheral. But it has limitations, >> as all the buffers should be aligned on block size (except the last one). >> But this cannot be guaranteed with SDIO. We should then have a property >> to disable the support of LLI. >> >> Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> > > Actually I think this is present also on the ux500 variants. See: > commit 2253ed4b36dc876d1598c4dab5587e537ec68c34 > "mmc: mmci: Support any block sizes for ux500v2 and qcom variant" > > Spot the variant data "dma_power_of_2". > > So whatever property you add > to the variant data (not in the device tree please) should > be added to the ux500 variants as well, it will *VERY* likely > have a problem with LLI elements not being a power of 2 > as it is the ancestor of later STMicro variants. > > It might actually be the reason for some annoying WiFi error > messages I have seen :/ > > Yours, > Linus Walleij Hi Linus, The STM32 variant uses an internal DMA, and the DMA functions are in its dedicated file. So I was planning to do the same as what is done in meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA constraints are not fulfilled. Not sure it can help for Ux500. Ulf, before I send my new series (although it is not ready yet), would you be OK with the bounce buffer idea? Best regards, Yann
On Tue, 15 Mar 2022 at 09:26, Yann Gautier <yann.gautier@foss.st.com> wrote: > > On 3/14/22 23:43, Linus Walleij wrote: > > "On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier <yann.gautier@foss.st.com> wrote: > > > >> On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported > >> starting from revision v2 of the peripheral. But it has limitations, > >> as all the buffers should be aligned on block size (except the last one). > >> But this cannot be guaranteed with SDIO. We should then have a property > >> to disable the support of LLI. > >> > >> Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> > > > > Actually I think this is present also on the ux500 variants. See: > > commit 2253ed4b36dc876d1598c4dab5587e537ec68c34 > > "mmc: mmci: Support any block sizes for ux500v2 and qcom variant" > > > > Spot the variant data "dma_power_of_2". > > > > So whatever property you add > > to the variant data (not in the device tree please) should > > be added to the ux500 variants as well, it will *VERY* likely > > have a problem with LLI elements not being a power of 2 > > as it is the ancestor of later STMicro variants. > > > > It might actually be the reason for some annoying WiFi error > > messages I have seen :/ > > > > Yours, > > Linus Walleij > > Hi Linus, > > The STM32 variant uses an internal DMA, and the DMA functions are in its > dedicated file. So I was planning to do the same as what is done in > meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA > constraints are not fulfilled. Not sure it can help for Ux500. We already have a bounce buffer in mmci_pio_read(), but we need one in mmc_pio_write() too, which hasn't been implemented yet. > > Ulf, before I send my new series (although it is not ready yet), would > you be OK with the bounce buffer idea? Yes, that works for me. On the other hand, it would be even better if we could specify the buffer limitations per mmc host instance, so upper layers (SDIO func drivers) could conform to these - and use better buffers, to achieve a better performance. > > > Best regards, > Yann Kind regards Uffe
On 3/17/22 11:00, Ulf Hansson wrote: > On Tue, 15 Mar 2022 at 09:26, Yann Gautier <yann.gautier@foss.st.com> wrote: >> >> On 3/14/22 23:43, Linus Walleij wrote: >>> "On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier <yann.gautier@foss.st.com> wrote: >>> >>>> On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported >>>> starting from revision v2 of the peripheral. But it has limitations, >>>> as all the buffers should be aligned on block size (except the last one). >>>> But this cannot be guaranteed with SDIO. We should then have a property >>>> to disable the support of LLI. >>>> >>>> Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> >>> >>> Actually I think this is present also on the ux500 variants. See: >>> commit 2253ed4b36dc876d1598c4dab5587e537ec68c34 >>> "mmc: mmci: Support any block sizes for ux500v2 and qcom variant" >>> >>> Spot the variant data "dma_power_of_2". >>> >>> So whatever property you add >>> to the variant data (not in the device tree please) should >>> be added to the ux500 variants as well, it will *VERY* likely >>> have a problem with LLI elements not being a power of 2 >>> as it is the ancestor of later STMicro variants. >>> >>> It might actually be the reason for some annoying WiFi error >>> messages I have seen :/ >>> >>> Yours, >>> Linus Walleij >> >> Hi Linus, >> >> The STM32 variant uses an internal DMA, and the DMA functions are in its >> dedicated file. So I was planning to do the same as what is done in >> meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA >> constraints are not fulfilled. Not sure it can help for Ux500. > Hi Ulf, > We already have a bounce buffer in mmci_pio_read(), but we need one in > mmc_pio_write() too, which hasn't been implemented yet. The idea is to keep using our internal DMA, and not switch to pio mode. > >> >> Ulf, before I send my new series (although it is not ready yet), would >> you be OK with the bounce buffer idea? > > Yes, that works for me. I have patches almost ready, I'll send that soon. > > On the other hand, it would be even better if we could specify the > buffer limitations per mmc host instance, so upper layers (SDIO func > drivers) could conform to these - and use better buffers, to achieve a > better performance. We've seen things that could be improved in the wifi driver. I'll check what could be done. Best regards, Yann > >> >> >> Best regards, >> Yann > > Kind regards > Uffe
On Thu, 17 Mar 2022 at 11:18, Yann Gautier <yann.gautier@foss.st.com> wrote: > > On 3/17/22 11:00, Ulf Hansson wrote: > > On Tue, 15 Mar 2022 at 09:26, Yann Gautier <yann.gautier@foss.st.com> wrote: > >> > >> On 3/14/22 23:43, Linus Walleij wrote: > >>> "On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier <yann.gautier@foss.st.com> wrote: > >>> > >>>> On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported > >>>> starting from revision v2 of the peripheral. But it has limitations, > >>>> as all the buffers should be aligned on block size (except the last one). > >>>> But this cannot be guaranteed with SDIO. We should then have a property > >>>> to disable the support of LLI. > >>>> > >>>> Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> > >>> > >>> Actually I think this is present also on the ux500 variants. See: > >>> commit 2253ed4b36dc876d1598c4dab5587e537ec68c34 > >>> "mmc: mmci: Support any block sizes for ux500v2 and qcom variant" > >>> > >>> Spot the variant data "dma_power_of_2". > >>> > >>> So whatever property you add > >>> to the variant data (not in the device tree please) should > >>> be added to the ux500 variants as well, it will *VERY* likely > >>> have a problem with LLI elements not being a power of 2 > >>> as it is the ancestor of later STMicro variants. > >>> > >>> It might actually be the reason for some annoying WiFi error > >>> messages I have seen :/ > >>> > >>> Yours, > >>> Linus Walleij > >> > >> Hi Linus, > >> > >> The STM32 variant uses an internal DMA, and the DMA functions are in its > >> dedicated file. So I was planning to do the same as what is done in > >> meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA > >> constraints are not fulfilled. Not sure it can help for Ux500. > > > > Hi Ulf, > > > We already have a bounce buffer in mmci_pio_read(), but we need one in > > mmc_pio_write() too, which hasn't been implemented yet. > > The idea is to keep using our internal DMA, and not switch to pio mode. Okay, but doesn't that become awfully inefficient, especially if we end up with several smaller sg-list-elements. The switch to pio would only be temporary for the particular request that has "bogus" buffers. > > > > >> > >> Ulf, before I send my new series (although it is not ready yet), would > >> you be OK with the bounce buffer idea? > > > > Yes, that works for me. > I have patches almost ready, I'll send that soon. Okay! > > > > > On the other hand, it would be even better if we could specify the > > buffer limitations per mmc host instance, so upper layers (SDIO func > > drivers) could conform to these - and use better buffers, to achieve a > > better performance. > > We've seen things that could be improved in the wifi driver. I'll check > what could be done. Great! Kind regards Uffe
On Tue, Mar 15, 2022 at 9:26 AM Yann Gautier <yann.gautier@foss.st.com> wrote: > The STM32 variant uses an internal DMA, and the DMA functions are in its > dedicated file. So I was planning to do the same as what is done in > meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA > constraints are not fulfilled. Not sure it can help for Ux500. > > Ulf, before I send my new series (although it is not ready yet), would > you be OK with the bounce buffer idea? Would it not be better if the bounce buffer is something available for all MMCI variants and not restricted to the STM32 DMA add-on? What I'm thinking is that this is a problem with the MMCI hardware rather than with the DMA hardware, so the problem kind of gets fixed in the wrong place if the bounce buffer is in the DMA add-on code. Maybe this is how you fixed it in later patches, I'll take a look. Yours, Linus Walleij
On 3/25/22 21:12, Linus Walleij wrote: > On Tue, Mar 15, 2022 at 9:26 AM Yann Gautier <yann.gautier@foss.st.com> wrote: > >> The STM32 variant uses an internal DMA, and the DMA functions are in its >> dedicated file. So I was planning to do the same as what is done in >> meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA >> constraints are not fulfilled. Not sure it can help for Ux500. >> >> Ulf, before I send my new series (although it is not ready yet), would >> you be OK with the bounce buffer idea? > Hi Linus, > Would it not be better if the bounce buffer is something available > for all MMCI variants and not restricted to the STM32 DMA add-on? The issue was seen with the internal DMA of the STM32 variant of PL180. > > What I'm thinking is that this is a problem with the MMCI hardware > rather than with the DMA hardware, so the problem kind of gets > fixed in the wrong place if the bounce buffer is in the DMA add-on > code. > > Maybe this is how you fixed it in later patches, I'll take a look. I've pushed a new version there to correct latest remarks from Ulf: https://lore.kernel.org/all/20220328145114.334577-1-yann.gautier@foss.st.com/ > > Yours, > Linus Walleij Best regards, Yann
On Tue, Mar 15, 2022 at 09:26:01AM +0100, Yann Gautier wrote: > On 3/14/22 23:43, Linus Walleij wrote: > > "On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier <yann.gautier@foss.st.com> wrote: > > > > > On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported > > > starting from revision v2 of the peripheral. But it has limitations, > > > as all the buffers should be aligned on block size (except the last one). > > > But this cannot be guaranteed with SDIO. We should then have a property > > > to disable the support of LLI. > > > > > > Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> > > > > Actually I think this is present also on the ux500 variants. See: > > commit 2253ed4b36dc876d1598c4dab5587e537ec68c34 > > "mmc: mmci: Support any block sizes for ux500v2 and qcom variant" > > > > Spot the variant data "dma_power_of_2". > > > > So whatever property you add > > to the variant data (not in the device tree please) should > > be added to the ux500 variants as well, it will *VERY* likely > > have a problem with LLI elements not being a power of 2 > > as it is the ancestor of later STMicro variants. > > > > It might actually be the reason for some annoying WiFi error > > messages I have seen :/ > > > > Yours, > > Linus Walleij > > Hi Linus, > > The STM32 variant uses an internal DMA, and the DMA functions are in its > dedicated file. So I was planning to do the same as what is done in > meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA > constraints are not fulfilled. Not sure it can help for Ux500. > Irrelevant to this patch: May I know why the internal DMA cannot be represented as a dmaengine driver? We started seeing these internal DMA implementations in the other subsystems as well with pointers towards MMC core [1]. Thanks, Mani [1] https://lore.kernel.org/all/CA+V-a8tfUgvzPyMe_FHuz=8mmC6dPHP7E=e+nCzOey04vCcAkg@mail.gmail.com/ > Ulf, before I send my new series (although it is not ready yet), would you > be OK with the bounce buffer idea? > > > Best regards, > Yann
On 3/29/22 17:31, Manivannan Sadhasivam wrote: > On Tue, Mar 15, 2022 at 09:26:01AM +0100, Yann Gautier wrote: >> On 3/14/22 23:43, Linus Walleij wrote: >>> "On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier <yann.gautier@foss.st.com> wrote: >>> >>>> On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported >>>> starting from revision v2 of the peripheral. But it has limitations, >>>> as all the buffers should be aligned on block size (except the last one). >>>> But this cannot be guaranteed with SDIO. We should then have a property >>>> to disable the support of LLI. >>>> >>>> Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> >>> >>> Actually I think this is present also on the ux500 variants. See: >>> commit 2253ed4b36dc876d1598c4dab5587e537ec68c34 >>> "mmc: mmci: Support any block sizes for ux500v2 and qcom variant" >>> >>> Spot the variant data "dma_power_of_2". >>> >>> So whatever property you add >>> to the variant data (not in the device tree please) should >>> be added to the ux500 variants as well, it will *VERY* likely >>> have a problem with LLI elements not being a power of 2 >>> as it is the ancestor of later STMicro variants. >>> >>> It might actually be the reason for some annoying WiFi error >>> messages I have seen :/ >>> >>> Yours, >>> Linus Walleij >> >> Hi Linus, >> >> The STM32 variant uses an internal DMA, and the DMA functions are in its >> dedicated file. So I was planning to do the same as what is done in >> meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA >> constraints are not fulfilled. Not sure it can help for Ux500. >> Hi Mani, > > Irrelevant to this patch: May I know why the internal DMA cannot be represented > as a dmaengine driver? We started seeing these internal DMA implementations in > the other subsystems as well with pointers towards MMC core [1]. As for Prabhakar's answer, the IDMA here is inside our IP, and not used in any other IP. So I'm not sure it is really relevant to move that to another dmaengine driver. > > Thanks, > Mani Best regards, Yann > > [1] https://lore.kernel.org/all/CA+V-a8tfUgvzPyMe_FHuz=8mmC6dPHP7E=e+nCzOey04vCcAkg@mail.gmail.com/ > >> Ulf, before I send my new series (although it is not ready yet), would you >> be OK with the bounce buffer idea? >> >> >> Best regards, >> Yann
On Tue, Mar 29, 2022 at 06:00:26PM +0200, Yann Gautier wrote: > On 3/29/22 17:31, Manivannan Sadhasivam wrote: > > On Tue, Mar 15, 2022 at 09:26:01AM +0100, Yann Gautier wrote: > > > On 3/14/22 23:43, Linus Walleij wrote: > > > > "On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier <yann.gautier@foss.st.com> wrote: > > > > > > > > > On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported > > > > > starting from revision v2 of the peripheral. But it has limitations, > > > > > as all the buffers should be aligned on block size (except the last one). > > > > > But this cannot be guaranteed with SDIO. We should then have a property > > > > > to disable the support of LLI. > > > > > > > > > > Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> > > > > > > > > Actually I think this is present also on the ux500 variants. See: > > > > commit 2253ed4b36dc876d1598c4dab5587e537ec68c34 > > > > "mmc: mmci: Support any block sizes for ux500v2 and qcom variant" > > > > > > > > Spot the variant data "dma_power_of_2". > > > > > > > > So whatever property you add > > > > to the variant data (not in the device tree please) should > > > > be added to the ux500 variants as well, it will *VERY* likely > > > > have a problem with LLI elements not being a power of 2 > > > > as it is the ancestor of later STMicro variants. > > > > > > > > It might actually be the reason for some annoying WiFi error > > > > messages I have seen :/ > > > > > > > > Yours, > > > > Linus Walleij > > > > > > Hi Linus, > > > > > > The STM32 variant uses an internal DMA, and the DMA functions are in its > > > dedicated file. So I was planning to do the same as what is done in > > > meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA > > > constraints are not fulfilled. Not sure it can help for Ux500. > > > > > Hi Mani, > > > > > Irrelevant to this patch: May I know why the internal DMA cannot be represented > > as a dmaengine driver? We started seeing these internal DMA implementations in > > the other subsystems as well with pointers towards MMC core [1]. > > As for Prabhakar's answer, the IDMA here is inside our IP, and not used in > any other IP. So I'm not sure it is really relevant to move that to another > dmaengine driver. > Okay, I think this justification makes sense. I was worried of DMA IPs that get sandwiched into many peripherals like the one on Renesas platforms. It turned out that each subsystem has to add internal DMA support for it :/ Ulf, your thoughts? Thanks, Mani > > > > Thanks, > > Mani > > Best regards, > Yann > > > > > [1] https://lore.kernel.org/all/CA+V-a8tfUgvzPyMe_FHuz=8mmC6dPHP7E=e+nCzOey04vCcAkg@mail.gmail.com/ > > > > > Ulf, before I send my new series (although it is not ready yet), would you > > > be OK with the bounce buffer idea? > > > > > > > > > Best regards, > > > Yann >
On Tue, Mar 29, 2022 at 7:33 PM Manivannan Sadhasivam <mani@kernel.org> wrote: > [Yann] > > As for Prabhakar's answer, the IDMA here is inside our IP, and not used in > > any other IP. So I'm not sure it is really relevant to move that to another > > dmaengine driver. > > Okay, I think this justification makes sense. I was worried of DMA IPs that get > sandwiched into many peripherals like the one on Renesas platforms. It turned > out that each subsystem has to add internal DMA support for it :/ That is a justified worry. Qualcomm has "BAM DMA" (I think it is called?) which is added to each IP that needs DMA. drivers/mmc/host/mmci_qcom_dml.c It's for older Qualcomm platforms but I *think* it is actually not just used for the MMCI, just noone ever got around to adding it to any other peripheral? Srini do you know? Yours, Linus Walleij
On 29/03/2022 22:16, Linus Walleij wrote: > On Tue, Mar 29, 2022 at 7:33 PM Manivannan Sadhasivam <mani@kernel.org> wrote: >> [Yann] >>> As for Prabhakar's answer, the IDMA here is inside our IP, and not used in >>> any other IP. So I'm not sure it is really relevant to move that to another >>> dmaengine driver. >> >> Okay, I think this justification makes sense. I was worried of DMA IPs that get >> sandwiched into many peripherals like the one on Renesas platforms. It turned >> out that each subsystem has to add internal DMA support for it :/ > > That is a justified worry. > > Qualcomm has "BAM DMA" (I think it is called?) which is added to each IP > that needs DMA. drivers/mmc/host/mmci_qcom_dml.c > It's for older Qualcomm platforms but I *think* it is actually not just used > for the MMCI, just noone ever got around to adding it to any other > peripheral? Srini do you know? There are multiple instances of BAM (Bus access manager) on Qcom SoC, some of these instances are dedicated for each peripheral instance. In this particular case we have 4 instances of BAM each of which are dedicated to 4 instances of SD Controllers. BAM dmaengine is used across many Qualcomm peripheral drivers. --srini > > Yours, > Linus Walleij
diff --git a/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml b/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml index 1e69a5a42439..309a2c0426e5 100644 --- a/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml +++ b/Documentation/devicetree/bindings/mmc/arm,pl18x.yaml @@ -145,6 +145,11 @@ properties: driver to sample the receive data (for example with a voltage switch transceiver). + st,disable-dma-lli: + $ref: /schemas/types.yaml#/definitions/flag + description: ST Micro-specific property, disable DMA linked lists. + It is used for SDIO. + st,cmd-gpios: maxItems: 1 description:
On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported starting from revision v2 of the peripheral. But it has limitations, as all the buffers should be aligned on block size (except the last one). But this cannot be guaranteed with SDIO. We should then have a property to disable the support of LLI. Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> --- Documentation/devicetree/bindings/mmc/arm,pl18x.yaml | 5 +++++ 1 file changed, 5 insertions(+)